Kathleen Rowland, MD

Evidence summary

The Centers for Disease Control and Prevention (CDC) doesn’t use the term obesity to describe weight in children. Instead, the CDC defines overweight as body mass index (BMI) or weight-for-length for age and sex greater than the 95th percentile. Children above the 85th percentile are called “at risk for overweight.” A national expert panel recently recommended changing “at risk for overweight” to “overweight” and “overweight” to “obese”—the terminology used in this Clinical Inquiry.³

Studies find a clear connection

A 2008 systematic review found 25 prospective or retrospective longitudinal studies that examined the risk of overweight in adulthood based on overweight in childhood or adolescence. Studies had to include at least 1 anthropomorphic measurement before age 18 and at least 1 after age 18. The informativeness and validity of the studies were assessed using a standard evaluation tool. Because the review sought to provide results that could be generalized to large populations, it didn’t include studies of specific populations, such as former premature infants.

All of the 13 studies judged to be high quality found an elevated RR or odds ratio (OR) for adult obesity among participants who had been overweight as children. The authors didn’t calculate a composite measure of effect, but RRs in the individual studies ranged from 1.9 to 10.1.⁴

Older overweight children are at heightened risk

The systematic review considered children (≤12 years) and adolescents (>12 years) separately. Four high-quality studies assessed how many overweight children became overweight adults; 2 high-quality studies examined how many overweight children became obese adults. Overweight children had RRs between 1.9 and 3.6 for being overweight in adulthood compared with average-weight children; 1 study reported an OR of 7.0.

One study showed older overweight children to be at greater risk than younger children for overweight in adulthood: children who were overweight at 2 years of age had an RR of 2.7, whereas children who were overweight at 11 years had an RR of 3.6.

Obese children had similar results. A study of 4 age cohorts showed that children who were obese at 1 or 2 years of age had an OR of 1.3 for obesity in adulthood compared with average-weight peers. Obese children in the 3- to 5-year-old cohort had an OR of 4.7; obese children in the 6- to 9-year-old cohort had an OR of 8.8; and obese 10- to 14-year-olds had an OR of 22.3.

Risk increases with age

As with children, overweight adolescents had a higher risk of being overweight in adulthood. And the association between older age and higher ORs persisted into adolescence. One study found an OR of 17.5 for adult overweight among youngsters who were overweight at 10 to 14 years of age and an OR of 22.3 for adolescents who were overweight at 15 to 17 years.

Boys are at greater risk than girls

The systematic review also revealed sex differences. Two studies showed that overweight or obese boys were not only more likely to be overweight in adulthood than their average-weight peers (OR=15.0 in 1 study; RR=9.8 in the other), but also more likely to be overweight later in life than overweight or obese girls. The girls had an OR of 12.0 for adult overweight in 1 study and an RR of 6.8 in the other.

Recommendations

The American Academy of Family Physicians emphasizes that weight management in childhood is an important goal, but notes a lack of evidence regarding the effectiveness of screening and treating overweight in children.⁵ The American Academy of Pediatrics recommends calculating and plotting BMI yearly to identify excessive weight gain.⁶

The United States Preventive Services Task Force, citing lack of evidence for treatment benefit, finds insufficient evidence for or against screening for overweight in children.⁷

Evidence summary

The Centers for Disease Control and Prevention (CDC) doesn’t use the term obesity to describe weight in children. Instead, the CDC defines overweight as body mass index (BMI) or weight-for-length for age and sex greater than the 95th percentile. Children above the 85th percentile are called “at risk for overweight.” A national expert panel recently recommended changing “at risk for overweight” to “overweight” and “overweight” to “obese”—the terminology used in this Clinical Inquiry.³

Studies find a clear connection

A 2008 systematic review found 25 prospective or retrospective longitudinal studies that examined the risk of overweight in adulthood based on overweight in childhood or adolescence. Studies had to include at least 1 anthropomorphic measurement before age 18 and at least 1 after age 18. The informativeness and validity of the studies were assessed using a standard evaluation tool. Because the review sought to provide results that could be generalized to large populations, it didn’t include studies of specific populations, such as former premature infants.

All of the 13 studies judged to be high quality found an elevated RR or odds ratio (OR) for adult obesity among participants who had been overweight as children. The authors didn’t calculate a composite measure of effect, but RRs in the individual studies ranged from 1.9 to 10.1.⁴

Older overweight children are at heightened risk

The systematic review considered children (≤12 years) and adolescents (>12 years) separately. Four high-quality studies assessed how many overweight children became overweight adults; 2 high-quality studies examined how many overweight children became obese adults. Overweight children had RRs between 1.9 and 3.6 for being overweight in adulthood compared with average-weight children; 1 study reported an OR of 7.0.

One study showed older overweight children to be at greater risk than younger children for overweight in adulthood: children who were overweight at 2 years of age had an RR of 2.7, whereas children who were overweight at 11 years had an RR of 3.6.

Obese children had similar results. A study of 4 age cohorts showed that children who were obese at 1 or 2 years of age had an OR of 1.3 for obesity in adulthood compared with average-weight peers. Obese children in the 3- to 5-year-old cohort had an OR of 4.7; obese children in the 6- to 9-year-old cohort had an OR of 8.8; and obese 10- to 14-year-olds had an OR of 22.3.

Risk increases with age

As with children, overweight adolescents had a higher risk of being overweight in adulthood. And the association between older age and higher ORs persisted into adolescence. One study found an OR of 17.5 for adult overweight among youngsters who were overweight at 10 to 14 years of age and an OR of 22.3 for adolescents who were overweight at 15 to 17 years.

Boys are at greater risk than girls

The systematic review also revealed sex differences. Two studies showed that overweight or obese boys were not only more likely to be overweight in adulthood than their average-weight peers (OR=15.0 in 1 study; RR=9.8 in the other), but also more likely to be overweight later in life than overweight or obese girls. The girls had an OR of 12.0 for adult overweight in 1 study and an RR of 6.8 in the other.

Recommendations

The American Academy of Family Physicians emphasizes that weight management in childhood is an important goal, but notes a lack of evidence regarding the effectiveness of screening and treating overweight in children.⁵ The American Academy of Pediatrics recommends calculating and plotting BMI yearly to identify excessive weight gain.⁶

The United States Preventive Services Task Force, citing lack of evidence for treatment benefit, finds insufficient evidence for or against screening for overweight in children.⁷

Evidence summary

The Centers for Disease Control and Prevention (CDC) doesn’t use the term obesity to describe weight in children. Instead, the CDC defines overweight as body mass index (BMI) or weight-for-length for age and sex greater than the 95th percentile. Children above the 85th percentile are called “at risk for overweight.” A national expert panel recently recommended changing “at risk for overweight” to “overweight” and “overweight” to “obese”—the terminology used in this Clinical Inquiry.³

Studies find a clear connection

A 2008 systematic review found 25 prospective or retrospective longitudinal studies that examined the risk of overweight in adulthood based on overweight in childhood or adolescence. Studies had to include at least 1 anthropomorphic measurement before age 18 and at least 1 after age 18. The informativeness and validity of the studies were assessed using a standard evaluation tool. Because the review sought to provide results that could be generalized to large populations, it didn’t include studies of specific populations, such as former premature infants.

All of the 13 studies judged to be high quality found an elevated RR or odds ratio (OR) for adult obesity among participants who had been overweight as children. The authors didn’t calculate a composite measure of effect, but RRs in the individual studies ranged from 1.9 to 10.1.⁴

Older overweight children are at heightened risk

The systematic review considered children (≤12 years) and adolescents (>12 years) separately. Four high-quality studies assessed how many overweight children became overweight adults; 2 high-quality studies examined how many overweight children became obese adults. Overweight children had RRs between 1.9 and 3.6 for being overweight in adulthood compared with average-weight children; 1 study reported an OR of 7.0.

One study showed older overweight children to be at greater risk than younger children for overweight in adulthood: children who were overweight at 2 years of age had an RR of 2.7, whereas children who were overweight at 11 years had an RR of 3.6.

Obese children had similar results. A study of 4 age cohorts showed that children who were obese at 1 or 2 years of age had an OR of 1.3 for obesity in adulthood compared with average-weight peers. Obese children in the 3- to 5-year-old cohort had an OR of 4.7; obese children in the 6- to 9-year-old cohort had an OR of 8.8; and obese 10- to 14-year-olds had an OR of 22.3.

Risk increases with age

As with children, overweight adolescents had a higher risk of being overweight in adulthood. And the association between older age and higher ORs persisted into adolescence. One study found an OR of 17.5 for adult overweight among youngsters who were overweight at 10 to 14 years of age and an OR of 22.3 for adolescents who were overweight at 15 to 17 years.

Boys are at greater risk than girls

The systematic review also revealed sex differences. Two studies showed that overweight or obese boys were not only more likely to be overweight in adulthood than their average-weight peers (OR=15.0 in 1 study; RR=9.8 in the other), but also more likely to be overweight later in life than overweight or obese girls. The girls had an OR of 12.0 for adult overweight in 1 study and an RR of 6.8 in the other.

Recommendations

The American Academy of Family Physicians emphasizes that weight management in childhood is an important goal, but notes a lack of evidence regarding the effectiveness of screening and treating overweight in children.⁵ The American Academy of Pediatrics recommends calculating and plotting BMI yearly to identify excessive weight gain.⁶

The United States Preventive Services Task Force, citing lack of evidence for treatment benefit, finds insufficient evidence for or against screening for overweight in children.⁷

Evidence summary

Feeding difficulties, inadequate weight gain, and unusual physical exam findings may lead providers to assess thyroid function in newborns. Additionally, while measurement of free T4 is more common, some states use TSH as the required newborn screening assay to evaluate for congenital hypothyroidism. Whether ordered as a screening test or in response to symptoms, an elevated TSH in a newborn requires further investigation.

Congenital hypothyroidism is the most serious cause of an elevated TSH in a newborn. If left untreated, congenital hypothyroidism leads to developmental delay and mental retardation; however, with early treatment, intellectual outcomes are greatly improved. Newborns with an elevated TSH should be evaluated with repeat TSH and free T4 measurements in order to assess for congenital hypothyroidism.

TSH >50 mU/L increases chances of congenital hypothyroidism

Not surprisingly, higher levels of TSH increase the likelihood of congenital hypothyroidism. A study from the Netherlands examined diagnoses of infants with an increased TSH on newborn screening heelstick. Of 112 newborns with a TSH >50 mU/L, 110 (98%) had congenital hypothyroidism on further examination. However, only 34 of 594 (5.7%) newborns with a TSH between 9 and 20 mU/L were diagnosed with congenital hypothyroidism. Nineteen of 46 newborns (41%) with levels between 20 and 50 mU/L had congenital hypothyroidism.¹

Other common causes of hypothyroidism

While TSH is generally an accurate measurement of thyroid function, other factors can also lead to an elevated level. The same Dutch study mentioned above explored the presumed causes of elevated TSH among children who were diagnosed with transient hypothyroidism (initially elevated TSH level found to be normal on follow-up testing). The most common causes were thyroid-binding globulin deficiency (200/548 or 36% of newborns with transient hypothyroidism), severe illness (36%), prematurity (8%), and errors in screening procedures (4%).

Another study confirmed that TSH levels were higher in infants born preterm; babies with the earliest gestational ages had the highest TSH levels. The same study also found that TSH levels increased with increasing degrees of illness. Very preterm babies, those with cerebral pathology, low Apgar scores, respiratory distress syndrome, persistent ductus arteriosus requiring treatment, and necrotizing enterocolitis were at highest risk for having abnormally elevated TSH levels in this study.² If a sample is drawn from a newborn exhibiting symptoms (such as poor feeding or hypotonia), the TSH level may be elevated in spite of normal thyroid function.

Maternal thyroid disease can also cause a suppression of thyroid function in the newborn. One study¹ found that of 34 children with transient hypothyroidism, 10 had mothers with undertreated or unrecognized Graves disease.

Finally, either iodine excess or iodine deficiency can cause transient hypothyroidism. Case reports have directly demonstrated the effects of topical iodine exposure on newborn TSH levels.^3-5 Deficiency of dietary iodine is a common cause of both congenital and transient hypothyroidism in newborns worldwide, although it is rare in the United States. The World Health Organization lists 54 countries with inadequate iodine intake; consider children from these countries at high risk for hypothyroidism due to iodine deficiency.⁶

Draw TSH on the second or third day of life

In term, healthy newborns, TSH levels normally increase to levels of 60 mU/L within 30 minutes of delivery. This is followed by a rapid decline in TSH levels over the first 5 days of life to <10 mU/L. An Australian study found more elevated TSH levels for samples drawn on day 2 of life compared with day 3 of life, likely reflecting normal postnatal physiology.³ Age-specific reference ranges are necessary for interpretation of TSH levels during the first 5 days of life. The second or third day of life remains the optimal time for screening when appropriate reference ranges are used.

Recommendations from others

The United States Preventive Services Task Force (USPSTF),⁷ the American Academy of Family Physicians,⁸ the American Academy of Pediatrics,⁹ and the American Thyroid Association (ATA)¹⁰ all recommend routine screening of asymptomatic newborns for congenital hypothyroidism. The USPSTF recommends that clinicians evaluate abnormal thyroid screening results with a supplemental lab test, using TSH as the primary test and T4 as the supplemental test.⁷ Additionally, the ATA endorses a second thyroid screening at 7 to 14 days of life to increase specificity of congenital hypothyroidism screening.¹⁰

Evidence summary

Feeding difficulties, inadequate weight gain, and unusual physical exam findings may lead providers to assess thyroid function in newborns. Additionally, while measurement of free T4 is more common, some states use TSH as the required newborn screening assay to evaluate for congenital hypothyroidism. Whether ordered as a screening test or in response to symptoms, an elevated TSH in a newborn requires further investigation.

Congenital hypothyroidism is the most serious cause of an elevated TSH in a newborn. If left untreated, congenital hypothyroidism leads to developmental delay and mental retardation; however, with early treatment, intellectual outcomes are greatly improved. Newborns with an elevated TSH should be evaluated with repeat TSH and free T4 measurements in order to assess for congenital hypothyroidism.

TSH >50 mU/L increases chances of congenital hypothyroidism

Not surprisingly, higher levels of TSH increase the likelihood of congenital hypothyroidism. A study from the Netherlands examined diagnoses of infants with an increased TSH on newborn screening heelstick. Of 112 newborns with a TSH >50 mU/L, 110 (98%) had congenital hypothyroidism on further examination. However, only 34 of 594 (5.7%) newborns with a TSH between 9 and 20 mU/L were diagnosed with congenital hypothyroidism. Nineteen of 46 newborns (41%) with levels between 20 and 50 mU/L had congenital hypothyroidism.¹

Other common causes of hypothyroidism

While TSH is generally an accurate measurement of thyroid function, other factors can also lead to an elevated level. The same Dutch study mentioned above explored the presumed causes of elevated TSH among children who were diagnosed with transient hypothyroidism (initially elevated TSH level found to be normal on follow-up testing). The most common causes were thyroid-binding globulin deficiency (200/548 or 36% of newborns with transient hypothyroidism), severe illness (36%), prematurity (8%), and errors in screening procedures (4%).

Another study confirmed that TSH levels were higher in infants born preterm; babies with the earliest gestational ages had the highest TSH levels. The same study also found that TSH levels increased with increasing degrees of illness. Very preterm babies, those with cerebral pathology, low Apgar scores, respiratory distress syndrome, persistent ductus arteriosus requiring treatment, and necrotizing enterocolitis were at highest risk for having abnormally elevated TSH levels in this study.² If a sample is drawn from a newborn exhibiting symptoms (such as poor feeding or hypotonia), the TSH level may be elevated in spite of normal thyroid function.

Maternal thyroid disease can also cause a suppression of thyroid function in the newborn. One study¹ found that of 34 children with transient hypothyroidism, 10 had mothers with undertreated or unrecognized Graves disease.

Finally, either iodine excess or iodine deficiency can cause transient hypothyroidism. Case reports have directly demonstrated the effects of topical iodine exposure on newborn TSH levels.^3-5 Deficiency of dietary iodine is a common cause of both congenital and transient hypothyroidism in newborns worldwide, although it is rare in the United States. The World Health Organization lists 54 countries with inadequate iodine intake; consider children from these countries at high risk for hypothyroidism due to iodine deficiency.⁶

Draw TSH on the second or third day of life

In term, healthy newborns, TSH levels normally increase to levels of 60 mU/L within 30 minutes of delivery. This is followed by a rapid decline in TSH levels over the first 5 days of life to <10 mU/L. An Australian study found more elevated TSH levels for samples drawn on day 2 of life compared with day 3 of life, likely reflecting normal postnatal physiology.³ Age-specific reference ranges are necessary for interpretation of TSH levels during the first 5 days of life. The second or third day of life remains the optimal time for screening when appropriate reference ranges are used.

Recommendations from others

The United States Preventive Services Task Force (USPSTF),⁷ the American Academy of Family Physicians,⁸ the American Academy of Pediatrics,⁹ and the American Thyroid Association (ATA)¹⁰ all recommend routine screening of asymptomatic newborns for congenital hypothyroidism. The USPSTF recommends that clinicians evaluate abnormal thyroid screening results with a supplemental lab test, using TSH as the primary test and T4 as the supplemental test.⁷ Additionally, the ATA endorses a second thyroid screening at 7 to 14 days of life to increase specificity of congenital hypothyroidism screening.¹⁰

Evidence summary

Feeding difficulties, inadequate weight gain, and unusual physical exam findings may lead providers to assess thyroid function in newborns. Additionally, while measurement of free T4 is more common, some states use TSH as the required newborn screening assay to evaluate for congenital hypothyroidism. Whether ordered as a screening test or in response to symptoms, an elevated TSH in a newborn requires further investigation.

Congenital hypothyroidism is the most serious cause of an elevated TSH in a newborn. If left untreated, congenital hypothyroidism leads to developmental delay and mental retardation; however, with early treatment, intellectual outcomes are greatly improved. Newborns with an elevated TSH should be evaluated with repeat TSH and free T4 measurements in order to assess for congenital hypothyroidism.

TSH >50 mU/L increases chances of congenital hypothyroidism

Not surprisingly, higher levels of TSH increase the likelihood of congenital hypothyroidism. A study from the Netherlands examined diagnoses of infants with an increased TSH on newborn screening heelstick. Of 112 newborns with a TSH >50 mU/L, 110 (98%) had congenital hypothyroidism on further examination. However, only 34 of 594 (5.7%) newborns with a TSH between 9 and 20 mU/L were diagnosed with congenital hypothyroidism. Nineteen of 46 newborns (41%) with levels between 20 and 50 mU/L had congenital hypothyroidism.¹

Other common causes of hypothyroidism

While TSH is generally an accurate measurement of thyroid function, other factors can also lead to an elevated level. The same Dutch study mentioned above explored the presumed causes of elevated TSH among children who were diagnosed with transient hypothyroidism (initially elevated TSH level found to be normal on follow-up testing). The most common causes were thyroid-binding globulin deficiency (200/548 or 36% of newborns with transient hypothyroidism), severe illness (36%), prematurity (8%), and errors in screening procedures (4%).

Another study confirmed that TSH levels were higher in infants born preterm; babies with the earliest gestational ages had the highest TSH levels. The same study also found that TSH levels increased with increasing degrees of illness. Very preterm babies, those with cerebral pathology, low Apgar scores, respiratory distress syndrome, persistent ductus arteriosus requiring treatment, and necrotizing enterocolitis were at highest risk for having abnormally elevated TSH levels in this study.² If a sample is drawn from a newborn exhibiting symptoms (such as poor feeding or hypotonia), the TSH level may be elevated in spite of normal thyroid function.

Maternal thyroid disease can also cause a suppression of thyroid function in the newborn. One study¹ found that of 34 children with transient hypothyroidism, 10 had mothers with undertreated or unrecognized Graves disease.

Finally, either iodine excess or iodine deficiency can cause transient hypothyroidism. Case reports have directly demonstrated the effects of topical iodine exposure on newborn TSH levels.^3-5 Deficiency of dietary iodine is a common cause of both congenital and transient hypothyroidism in newborns worldwide, although it is rare in the United States. The World Health Organization lists 54 countries with inadequate iodine intake; consider children from these countries at high risk for hypothyroidism due to iodine deficiency.⁶

Draw TSH on the second or third day of life

In term, healthy newborns, TSH levels normally increase to levels of 60 mU/L within 30 minutes of delivery. This is followed by a rapid decline in TSH levels over the first 5 days of life to <10 mU/L. An Australian study found more elevated TSH levels for samples drawn on day 2 of life compared with day 3 of life, likely reflecting normal postnatal physiology.³ Age-specific reference ranges are necessary for interpretation of TSH levels during the first 5 days of life. The second or third day of life remains the optimal time for screening when appropriate reference ranges are used.

Recommendations from others

The United States Preventive Services Task Force (USPSTF),⁷ the American Academy of Family Physicians,⁸ the American Academy of Pediatrics,⁹ and the American Thyroid Association (ATA)¹⁰ all recommend routine screening of asymptomatic newborns for congenital hypothyroidism. The USPSTF recommends that clinicians evaluate abnormal thyroid screening results with a supplemental lab test, using TSH as the primary test and T4 as the supplemental test.⁷ Additionally, the ATA endorses a second thyroid screening at 7 to 14 days of life to increase specificity of congenital hypothyroidism screening.¹⁰

Illustrative case

Your first 4 patients this morning were a 50-year-old woman with metabolic syndrome, a 62-year-old obese man with high blood pressure, a 44-year-old woman with depression, and a 75-year-old man with a recent admission for myocardial infarction. In addition to managing their medications and reviewing lab results, you have already spent a lot of time discussing the benefits of exercise with each of these patients.

As you prepare to talk with your next patient—a 28-year-old woman with a BMI of 29 whose chief complaint is “wants to lose weight”—you wonder if there are any simple, brief, effective interventions to help your patients increase their physical activity.

BACKGROUND: A long way to go

Although there is no evidence that simply advising patients to walk has any effect, primary care physicians frequently recommend walking as a form of exercise—it is free, requires no special equipment, and is readily accessible to most motivated patients.

The Centers for Disease Control and Prevention recommends that adults engage in moderate physical activity for at least 30 minutes a day, at least 5 days per week.² Yet 40% of adults do not engage in any leisure-time physical activity. This percentage is higher in women (43%), African-Americans (52%), and Hispanics (54%).³

The health benefits of exercise are clear. Regular physical activity has been shown to decrease overweight and obesity.⁴ It has also been shown to improve control of type 2 diabetes⁵ and hypertension.⁶ Frequent exercise is associated with a decreased mortality rate.⁷ Walking has been shown to decrease the risk of cardiovascular events in women, regardless of BMI.⁸

Walking has similarly been shown to decrease overall mortality among men.⁹ Cardiovascular fitness has also been shown to decrease mortality in adults over 60, even in the absence of weight loss.¹⁰

CLINICAL CONTEXT: USPSTF: Advice alone won’t kick-start exercise

We realize, of course, that most of our adult patients could benefit from regular exercise. Exercise is included in the treatment guidelines for overweight/obesity, hypertension, type 2 diabetes, metabolic syndrome, cardiovascular disease, chronic pain, peripheral vascular disease, and depression.¹¹

Eureka! a simple, practical intervention

PURLs EDITOR
Bernard Ewigman. MD, MSPH
Department of Family Medicine
The University of Chicago
[email protected]

At last, the humble pedometer gives us a brief intervention for physical exercise that works. yes, we need more research for lots of reasons (always), but this Purl gives us a practical tool that can be recommended in a few minutes, consistent with the realities of daily practice.

The outcomes from this intervention are not dramatic. No lives were saved, no catastrophic diseases averted. yet regular exercise is so fundamentally important to just feeling good and having energy for daily life, not to mention lowering blood pressure and weight.

My guess is that this could become a handy recommendation used daily in family medicine and other primary care practices.

I am interested to know whether you already recommend pedometers to your patients. If not, does this seem like a worthwhile change in your practice?

On a personal note, I made a New year’s resolution to increase my physical activity. as soon as I finish this commentary, I am ordering a pedometer.

However, few office-based interventions have been shown to lead to increased physical activity. Patients sometimes resist making lifestyle changes, and providers are uncertain how to effectively promote physical activity. Furthermore, counseling patients to exercise without a specific intervention has not been shown to lead to long-term increases in physical activity. The US Preventive Services Task Force (USPSTF) finds there is insufficient evidence to recommend behavioral counseling alone for exercise, citing the lack of evidence for long-term efficacy.^12,13

STUDY SUMMARY: Pedometer users walked 2491 additional steps

This meta-analysis included 26 RCTs and observational studies of pedometer use in adult outpatients that reported a change in the number of steps walked per day. The 2767 participants in these studies were 85% women, with a mean age of 49. In the 7 studies that reported race, 93% of patients were white. At baseline, most participants were overweight, with normal blood pressure (mean 129/79 mm Hg) and relatively well-controlled lipid levels (mean total cholesterol 198 mg/dL, HDL 52 mg/dL, LDL 113 mg/dL). The mean baseline activity level was 7473 steps per day (range 2140–12,371). Duration of interventions ranged from 3 to 104 weeks, with a mean of 18 weeks. Sixteen of the studies used the Yamax pedometer, which has been validated for accuracy and reliability.

Participants in the RCTs who used pedometers increased their physical activity by 2491 steps per day more than controls. After excluding 1 study with a much higher increase in physical activity than the others, the increase was 2004 steps per day (95% confidence interval [CI], 878–3129; P<.001). In the observational studies, participants walked 2183 steps per day more than they had at baseline (95% CI, 1571–2796; P<.001). Overall, pedometer users increased their number of steps by 27% over baseline.

Step goal and step diary

Only studies that included a step goal and required participants to keep a step diary showed a significant increase in physical activity with pedometer use. There were no differences in outcomes based on duration of the intervention, inclusion of physical activity counseling, or the brand of pedometer used.

BMI and BP improved; lipids, glucose did not

Intervention participants had a statistically significant decrease in BMI of 0.38, which was associated with older age (P=.001), having a step goal (P=.04), and longer duration of the intervention (P=.07, trend). Intervention participants also had a significant decrease in systolic blood pressure of 3.8 mm Hg and diastolic blood pressure of 0.3 mm Hg (TABLE 1), which was associated with greater systolic blood pressure at baseline (P=.009).

There were no significant differences in serum lipids or fasting serum glucose in the studies that reported these variables.¹

TABLE 1
Pre- and post-intervention body mass index and blood pressure

WHAT’S NEW?: Weight loss without dieting

This study is the first large meta-analysis to show that pedometer use is an effective intervention for promoting physical activity. Another recent meta-analysis shows that pedometer use is also effective for short-term weight loss, even in the absence of dietary changes.¹⁴

Pedometers and goal-setting are simple, relatively inexpensive ways to help patients become physically active. According to systematic reviews,^15,16 telephone-based programs, encouraging stair use, and creating exercise space are other effective interventions to promote physical activity. Some of these interventions are at least as effective as pedometers; however, only encouraging stair walking and pedometer use are practical office-based interventions.

CAVEATS: Price and quality

A 2004 Consumer Reports article ranked pedometers by accuracy, ease of use, and features.¹⁷ Accurate step counts allow patients and physicians to assess whether step goals are being met. Pedometers are more accurate when recording fast walking (2.5–3.0 mph), compared with slow walking. Pedometers may therefore be less accurate in the elderly, very obese, or those who walk slowly.¹⁸

TABLE 2
Consumer Reports top-rated pedometers¹⁷

Negotiate the goal, patient keeps diary

Remember that patients must be counseled to set a step goal and keep a step diary. Most patients will have an initial step goal between 6000 and 10,000 steps per day. The step goal should be individualized to each patient’s current level of activity and gradually increased as activity level increases.

Schedule monthly or semi-monthly follow-up visits to evaluate progress towards activity or weight loss goals and to re-evaluate the step goal. Before beginning an exercise regimen, including walking, patients must be healthy enough for physical activity. In some cases, patients will need stress testing or other evaluation before using a pedometer to increase activity.

CHALLENGES TO IMPLEMENTATION: Time-wise

Counseling patients on the use of pedometers, and coaching them to set an appropriate step goal and keep a step diary, will take up time during the office visit, but it should be a brief intervention and therefore feasible.²¹

Organizing your office staff to assist you, and using a patient handout containing the basic information on pedometers, could reduce the demands on your time. Including information from the 2004 Consumer Reports article and Web sites with pedometers prices (such as www.pedometersusa.com and newlifestyles.com) should provide a good start for those patients who want more information.

PURLs methodology

This study was selected and evaluated using FPIN’s Priority Updates from the Research Literature (PURL) Surveillance System methodology. The criteria and findings leading to the selection of this study as a PURL can be accessed at www.jfponline.com/purls.

Illustrative case

Your first 4 patients this morning were a 50-year-old woman with metabolic syndrome, a 62-year-old obese man with high blood pressure, a 44-year-old woman with depression, and a 75-year-old man with a recent admission for myocardial infarction. In addition to managing their medications and reviewing lab results, you have already spent a lot of time discussing the benefits of exercise with each of these patients.

As you prepare to talk with your next patient—a 28-year-old woman with a BMI of 29 whose chief complaint is “wants to lose weight”—you wonder if there are any simple, brief, effective interventions to help your patients increase their physical activity.

BACKGROUND: A long way to go

Although there is no evidence that simply advising patients to walk has any effect, primary care physicians frequently recommend walking as a form of exercise—it is free, requires no special equipment, and is readily accessible to most motivated patients.

The Centers for Disease Control and Prevention recommends that adults engage in moderate physical activity for at least 30 minutes a day, at least 5 days per week.² Yet 40% of adults do not engage in any leisure-time physical activity. This percentage is higher in women (43%), African-Americans (52%), and Hispanics (54%).³

The health benefits of exercise are clear. Regular physical activity has been shown to decrease overweight and obesity.⁴ It has also been shown to improve control of type 2 diabetes⁵ and hypertension.⁶ Frequent exercise is associated with a decreased mortality rate.⁷ Walking has been shown to decrease the risk of cardiovascular events in women, regardless of BMI.⁸

Walking has similarly been shown to decrease overall mortality among men.⁹ Cardiovascular fitness has also been shown to decrease mortality in adults over 60, even in the absence of weight loss.¹⁰

CLINICAL CONTEXT: USPSTF: Advice alone won’t kick-start exercise

We realize, of course, that most of our adult patients could benefit from regular exercise. Exercise is included in the treatment guidelines for overweight/obesity, hypertension, type 2 diabetes, metabolic syndrome, cardiovascular disease, chronic pain, peripheral vascular disease, and depression.¹¹

Eureka! a simple, practical intervention

PURLs EDITOR
Bernard Ewigman. MD, MSPH
Department of Family Medicine
The University of Chicago
[email protected]

At last, the humble pedometer gives us a brief intervention for physical exercise that works. yes, we need more research for lots of reasons (always), but this Purl gives us a practical tool that can be recommended in a few minutes, consistent with the realities of daily practice.

The outcomes from this intervention are not dramatic. No lives were saved, no catastrophic diseases averted. yet regular exercise is so fundamentally important to just feeling good and having energy for daily life, not to mention lowering blood pressure and weight.

My guess is that this could become a handy recommendation used daily in family medicine and other primary care practices.

I am interested to know whether you already recommend pedometers to your patients. If not, does this seem like a worthwhile change in your practice?

On a personal note, I made a New year’s resolution to increase my physical activity. as soon as I finish this commentary, I am ordering a pedometer.

However, few office-based interventions have been shown to lead to increased physical activity. Patients sometimes resist making lifestyle changes, and providers are uncertain how to effectively promote physical activity. Furthermore, counseling patients to exercise without a specific intervention has not been shown to lead to long-term increases in physical activity. The US Preventive Services Task Force (USPSTF) finds there is insufficient evidence to recommend behavioral counseling alone for exercise, citing the lack of evidence for long-term efficacy.^12,13

STUDY SUMMARY: Pedometer users walked 2491 additional steps

This meta-analysis included 26 RCTs and observational studies of pedometer use in adult outpatients that reported a change in the number of steps walked per day. The 2767 participants in these studies were 85% women, with a mean age of 49. In the 7 studies that reported race, 93% of patients were white. At baseline, most participants were overweight, with normal blood pressure (mean 129/79 mm Hg) and relatively well-controlled lipid levels (mean total cholesterol 198 mg/dL, HDL 52 mg/dL, LDL 113 mg/dL). The mean baseline activity level was 7473 steps per day (range 2140–12,371). Duration of interventions ranged from 3 to 104 weeks, with a mean of 18 weeks. Sixteen of the studies used the Yamax pedometer, which has been validated for accuracy and reliability.

Participants in the RCTs who used pedometers increased their physical activity by 2491 steps per day more than controls. After excluding 1 study with a much higher increase in physical activity than the others, the increase was 2004 steps per day (95% confidence interval [CI], 878–3129; P<.001). In the observational studies, participants walked 2183 steps per day more than they had at baseline (95% CI, 1571–2796; P<.001). Overall, pedometer users increased their number of steps by 27% over baseline.

Step goal and step diary

Only studies that included a step goal and required participants to keep a step diary showed a significant increase in physical activity with pedometer use. There were no differences in outcomes based on duration of the intervention, inclusion of physical activity counseling, or the brand of pedometer used.

BMI and BP improved; lipids, glucose did not

Intervention participants had a statistically significant decrease in BMI of 0.38, which was associated with older age (P=.001), having a step goal (P=.04), and longer duration of the intervention (P=.07, trend). Intervention participants also had a significant decrease in systolic blood pressure of 3.8 mm Hg and diastolic blood pressure of 0.3 mm Hg (TABLE 1), which was associated with greater systolic blood pressure at baseline (P=.009).

There were no significant differences in serum lipids or fasting serum glucose in the studies that reported these variables.¹

TABLE 1
Pre- and post-intervention body mass index and blood pressure

WHAT’S NEW?: Weight loss without dieting

This study is the first large meta-analysis to show that pedometer use is an effective intervention for promoting physical activity. Another recent meta-analysis shows that pedometer use is also effective for short-term weight loss, even in the absence of dietary changes.¹⁴

Pedometers and goal-setting are simple, relatively inexpensive ways to help patients become physically active. According to systematic reviews,^15,16 telephone-based programs, encouraging stair use, and creating exercise space are other effective interventions to promote physical activity. Some of these interventions are at least as effective as pedometers; however, only encouraging stair walking and pedometer use are practical office-based interventions.

CAVEATS: Price and quality

A 2004 Consumer Reports article ranked pedometers by accuracy, ease of use, and features.¹⁷ Accurate step counts allow patients and physicians to assess whether step goals are being met. Pedometers are more accurate when recording fast walking (2.5–3.0 mph), compared with slow walking. Pedometers may therefore be less accurate in the elderly, very obese, or those who walk slowly.¹⁸

TABLE 2
Consumer Reports top-rated pedometers¹⁷

Negotiate the goal, patient keeps diary

Remember that patients must be counseled to set a step goal and keep a step diary. Most patients will have an initial step goal between 6000 and 10,000 steps per day. The step goal should be individualized to each patient’s current level of activity and gradually increased as activity level increases.

Schedule monthly or semi-monthly follow-up visits to evaluate progress towards activity or weight loss goals and to re-evaluate the step goal. Before beginning an exercise regimen, including walking, patients must be healthy enough for physical activity. In some cases, patients will need stress testing or other evaluation before using a pedometer to increase activity.

CHALLENGES TO IMPLEMENTATION: Time-wise

Counseling patients on the use of pedometers, and coaching them to set an appropriate step goal and keep a step diary, will take up time during the office visit, but it should be a brief intervention and therefore feasible.²¹

Organizing your office staff to assist you, and using a patient handout containing the basic information on pedometers, could reduce the demands on your time. Including information from the 2004 Consumer Reports article and Web sites with pedometers prices (such as www.pedometersusa.com and newlifestyles.com) should provide a good start for those patients who want more information.

PURLs methodology

This study was selected and evaluated using FPIN’s Priority Updates from the Research Literature (PURL) Surveillance System methodology. The criteria and findings leading to the selection of this study as a PURL can be accessed at www.jfponline.com/purls.

Illustrative case

Your first 4 patients this morning were a 50-year-old woman with metabolic syndrome, a 62-year-old obese man with high blood pressure, a 44-year-old woman with depression, and a 75-year-old man with a recent admission for myocardial infarction. In addition to managing their medications and reviewing lab results, you have already spent a lot of time discussing the benefits of exercise with each of these patients.

As you prepare to talk with your next patient—a 28-year-old woman with a BMI of 29 whose chief complaint is “wants to lose weight”—you wonder if there are any simple, brief, effective interventions to help your patients increase their physical activity.

BACKGROUND: A long way to go

Although there is no evidence that simply advising patients to walk has any effect, primary care physicians frequently recommend walking as a form of exercise—it is free, requires no special equipment, and is readily accessible to most motivated patients.

The Centers for Disease Control and Prevention recommends that adults engage in moderate physical activity for at least 30 minutes a day, at least 5 days per week.² Yet 40% of adults do not engage in any leisure-time physical activity. This percentage is higher in women (43%), African-Americans (52%), and Hispanics (54%).³

The health benefits of exercise are clear. Regular physical activity has been shown to decrease overweight and obesity.⁴ It has also been shown to improve control of type 2 diabetes⁵ and hypertension.⁶ Frequent exercise is associated with a decreased mortality rate.⁷ Walking has been shown to decrease the risk of cardiovascular events in women, regardless of BMI.⁸

Walking has similarly been shown to decrease overall mortality among men.⁹ Cardiovascular fitness has also been shown to decrease mortality in adults over 60, even in the absence of weight loss.¹⁰

CLINICAL CONTEXT: USPSTF: Advice alone won’t kick-start exercise

We realize, of course, that most of our adult patients could benefit from regular exercise. Exercise is included in the treatment guidelines for overweight/obesity, hypertension, type 2 diabetes, metabolic syndrome, cardiovascular disease, chronic pain, peripheral vascular disease, and depression.¹¹

Eureka! a simple, practical intervention

PURLs EDITOR
Bernard Ewigman. MD, MSPH
Department of Family Medicine
The University of Chicago
[email protected]

At last, the humble pedometer gives us a brief intervention for physical exercise that works. yes, we need more research for lots of reasons (always), but this Purl gives us a practical tool that can be recommended in a few minutes, consistent with the realities of daily practice.

The outcomes from this intervention are not dramatic. No lives were saved, no catastrophic diseases averted. yet regular exercise is so fundamentally important to just feeling good and having energy for daily life, not to mention lowering blood pressure and weight.

My guess is that this could become a handy recommendation used daily in family medicine and other primary care practices.

I am interested to know whether you already recommend pedometers to your patients. If not, does this seem like a worthwhile change in your practice?

On a personal note, I made a New year’s resolution to increase my physical activity. as soon as I finish this commentary, I am ordering a pedometer.

However, few office-based interventions have been shown to lead to increased physical activity. Patients sometimes resist making lifestyle changes, and providers are uncertain how to effectively promote physical activity. Furthermore, counseling patients to exercise without a specific intervention has not been shown to lead to long-term increases in physical activity. The US Preventive Services Task Force (USPSTF) finds there is insufficient evidence to recommend behavioral counseling alone for exercise, citing the lack of evidence for long-term efficacy.^12,13

STUDY SUMMARY: Pedometer users walked 2491 additional steps

This meta-analysis included 26 RCTs and observational studies of pedometer use in adult outpatients that reported a change in the number of steps walked per day. The 2767 participants in these studies were 85% women, with a mean age of 49. In the 7 studies that reported race, 93% of patients were white. At baseline, most participants were overweight, with normal blood pressure (mean 129/79 mm Hg) and relatively well-controlled lipid levels (mean total cholesterol 198 mg/dL, HDL 52 mg/dL, LDL 113 mg/dL). The mean baseline activity level was 7473 steps per day (range 2140–12,371). Duration of interventions ranged from 3 to 104 weeks, with a mean of 18 weeks. Sixteen of the studies used the Yamax pedometer, which has been validated for accuracy and reliability.

Participants in the RCTs who used pedometers increased their physical activity by 2491 steps per day more than controls. After excluding 1 study with a much higher increase in physical activity than the others, the increase was 2004 steps per day (95% confidence interval [CI], 878–3129; P<.001). In the observational studies, participants walked 2183 steps per day more than they had at baseline (95% CI, 1571–2796; P<.001). Overall, pedometer users increased their number of steps by 27% over baseline.

Step goal and step diary

Only studies that included a step goal and required participants to keep a step diary showed a significant increase in physical activity with pedometer use. There were no differences in outcomes based on duration of the intervention, inclusion of physical activity counseling, or the brand of pedometer used.

BMI and BP improved; lipids, glucose did not

Intervention participants had a statistically significant decrease in BMI of 0.38, which was associated with older age (P=.001), having a step goal (P=.04), and longer duration of the intervention (P=.07, trend). Intervention participants also had a significant decrease in systolic blood pressure of 3.8 mm Hg and diastolic blood pressure of 0.3 mm Hg (TABLE 1), which was associated with greater systolic blood pressure at baseline (P=.009).

There were no significant differences in serum lipids or fasting serum glucose in the studies that reported these variables.¹

TABLE 1
Pre- and post-intervention body mass index and blood pressure

WHAT’S NEW?: Weight loss without dieting

This study is the first large meta-analysis to show that pedometer use is an effective intervention for promoting physical activity. Another recent meta-analysis shows that pedometer use is also effective for short-term weight loss, even in the absence of dietary changes.¹⁴

Pedometers and goal-setting are simple, relatively inexpensive ways to help patients become physically active. According to systematic reviews,^15,16 telephone-based programs, encouraging stair use, and creating exercise space are other effective interventions to promote physical activity. Some of these interventions are at least as effective as pedometers; however, only encouraging stair walking and pedometer use are practical office-based interventions.

CAVEATS: Price and quality

A 2004 Consumer Reports article ranked pedometers by accuracy, ease of use, and features.¹⁷ Accurate step counts allow patients and physicians to assess whether step goals are being met. Pedometers are more accurate when recording fast walking (2.5–3.0 mph), compared with slow walking. Pedometers may therefore be less accurate in the elderly, very obese, or those who walk slowly.¹⁸

TABLE 2
Consumer Reports top-rated pedometers¹⁷

Negotiate the goal, patient keeps diary

Remember that patients must be counseled to set a step goal and keep a step diary. Most patients will have an initial step goal between 6000 and 10,000 steps per day. The step goal should be individualized to each patient’s current level of activity and gradually increased as activity level increases.

Schedule monthly or semi-monthly follow-up visits to evaluate progress towards activity or weight loss goals and to re-evaluate the step goal. Before beginning an exercise regimen, including walking, patients must be healthy enough for physical activity. In some cases, patients will need stress testing or other evaluation before using a pedometer to increase activity.

CHALLENGES TO IMPLEMENTATION: Time-wise

Counseling patients on the use of pedometers, and coaching them to set an appropriate step goal and keep a step diary, will take up time during the office visit, but it should be a brief intervention and therefore feasible.²¹

Organizing your office staff to assist you, and using a patient handout containing the basic information on pedometers, could reduce the demands on your time. Including information from the 2004 Consumer Reports article and Web sites with pedometers prices (such as www.pedometersusa.com and newlifestyles.com) should provide a good start for those patients who want more information.

PURLs methodology

This study was selected and evaluated using FPIN’s Priority Updates from the Research Literature (PURL) Surveillance System methodology. The criteria and findings leading to the selection of this study as a PURL can be accessed at www.jfponline.com/purls.

Evidence summary

In areas where tuberculosis is prevalent, the World Health Organization recommends BCG vaccination at birth, without booster doses, to prevent childhood complications of TB infection;¹ however, the vaccine’s efficacy is known to be inconsistent. Though BCG vaccine given at birth can decrease the risk of miliary TB and TB meningitis among children, estimates of its effectiveness in preventing adult pulmonary TB range widely from 0% to 80%.¹

Though prior BCG vaccination increases the risk of a reactive PPD, this effect is also known to be inconsistent. A 2002 meta-analysis showed that the person’s age at the time of their BCG vaccination and the years since vaccination influence the relative risk of a positive PPD (TABLE). The highest relative risk of a positive PPD occurred among patients who received BCG vaccination after infancy and within 15 years of the PPD testing. This same meta-analysis also examined the significance of the size of the PPD response; a subset of 4 studies showed that equal proportions of BCG vaccinated and unvaccinated patients had indurations of 14 mm or more.²

BCG vaccine may confound PPD readings, but several studies indicate that PPD can still be a useful screening tool for tuberculosis infection after vaccination. A Brazilian case-control study found that reactions by those BCG recipients later exposed to TB were significantly greater than those with no TB exposure.³ The study noted that 47.5% of exposed children (defined as those with a household contact) had PPD readings of >10 mm, compared with just 3.6% of control children. In a Quebec cohort of 1198 foreign-born children and young adults, prior BCG vaccination could account for 50% of PPDs with induration of 5 to 9 mm, but only 4% of reactions 10 mm or greater. This study also showed that patients from countries with a high or moderate incidence of TB were more likely to have reactive PPDs than those from countries of low incidence, suggesting that exposure to TB accounts for some of the positive PPDs.⁴

Where it is available, the QuantiFERON-TB Gold test may be used in place of, or in addition to, the PPD for patients who are known to have received a BCG vaccine. This blood test detects interferon-gamma in the serum of people sensitized to Mycobacterium tuberculosis. Because the test is specific to proteins found in M tuberculosis, there is no cross-reactivity with BCG. A Japanese study of 216 BCG-vaccinated individuals showed interferon-gamma assays to be 98.1% specific. The same study reported 89.0% sensitivity for the combination of 2 interferon-gamma assays among 118 TB culture-confirmed individuals.⁵ A published report estimated the cost to the health care system per patient tested by a single interferon-gamma release assay as $33.67, compared with approximately $11 for PPD testing.⁶

TABLE
PPD reactions >10 mm when BCG was given during and after infancy

Recommendations from others

While the US Preventive Services Task Force (USPSTF) does not make a specific recommendation regarding PPD readings after BCG vaccine, it does recommend screening high-risk populations. The USPSTF further notes that reactions >10 mm should not be attributed to prior BCG vaccine.⁷

The Centers for Disease Control and Prevention (CDC) and American Thoracic Society joint statement recommends against altering guidelines for testing and interpretation among BCG recipients.⁸ In 2005, the CDC recommended the QuantiFERON-TB Gold test be used under the same indications as the PPD, noting its potential benefit among those previously immunized with BCG.⁹

Evidence summary

In areas where tuberculosis is prevalent, the World Health Organization recommends BCG vaccination at birth, without booster doses, to prevent childhood complications of TB infection;¹ however, the vaccine’s efficacy is known to be inconsistent. Though BCG vaccine given at birth can decrease the risk of miliary TB and TB meningitis among children, estimates of its effectiveness in preventing adult pulmonary TB range widely from 0% to 80%.¹

Though prior BCG vaccination increases the risk of a reactive PPD, this effect is also known to be inconsistent. A 2002 meta-analysis showed that the person’s age at the time of their BCG vaccination and the years since vaccination influence the relative risk of a positive PPD (TABLE). The highest relative risk of a positive PPD occurred among patients who received BCG vaccination after infancy and within 15 years of the PPD testing. This same meta-analysis also examined the significance of the size of the PPD response; a subset of 4 studies showed that equal proportions of BCG vaccinated and unvaccinated patients had indurations of 14 mm or more.²

BCG vaccine may confound PPD readings, but several studies indicate that PPD can still be a useful screening tool for tuberculosis infection after vaccination. A Brazilian case-control study found that reactions by those BCG recipients later exposed to TB were significantly greater than those with no TB exposure.³ The study noted that 47.5% of exposed children (defined as those with a household contact) had PPD readings of >10 mm, compared with just 3.6% of control children. In a Quebec cohort of 1198 foreign-born children and young adults, prior BCG vaccination could account for 50% of PPDs with induration of 5 to 9 mm, but only 4% of reactions 10 mm or greater. This study also showed that patients from countries with a high or moderate incidence of TB were more likely to have reactive PPDs than those from countries of low incidence, suggesting that exposure to TB accounts for some of the positive PPDs.⁴

Where it is available, the QuantiFERON-TB Gold test may be used in place of, or in addition to, the PPD for patients who are known to have received a BCG vaccine. This blood test detects interferon-gamma in the serum of people sensitized to Mycobacterium tuberculosis. Because the test is specific to proteins found in M tuberculosis, there is no cross-reactivity with BCG. A Japanese study of 216 BCG-vaccinated individuals showed interferon-gamma assays to be 98.1% specific. The same study reported 89.0% sensitivity for the combination of 2 interferon-gamma assays among 118 TB culture-confirmed individuals.⁵ A published report estimated the cost to the health care system per patient tested by a single interferon-gamma release assay as $33.67, compared with approximately $11 for PPD testing.⁶

TABLE
PPD reactions >10 mm when BCG was given during and after infancy

Recommendations from others

While the US Preventive Services Task Force (USPSTF) does not make a specific recommendation regarding PPD readings after BCG vaccine, it does recommend screening high-risk populations. The USPSTF further notes that reactions >10 mm should not be attributed to prior BCG vaccine.⁷

The Centers for Disease Control and Prevention (CDC) and American Thoracic Society joint statement recommends against altering guidelines for testing and interpretation among BCG recipients.⁸ In 2005, the CDC recommended the QuantiFERON-TB Gold test be used under the same indications as the PPD, noting its potential benefit among those previously immunized with BCG.⁹

Evidence summary

In areas where tuberculosis is prevalent, the World Health Organization recommends BCG vaccination at birth, without booster doses, to prevent childhood complications of TB infection;¹ however, the vaccine’s efficacy is known to be inconsistent. Though BCG vaccine given at birth can decrease the risk of miliary TB and TB meningitis among children, estimates of its effectiveness in preventing adult pulmonary TB range widely from 0% to 80%.¹

Though prior BCG vaccination increases the risk of a reactive PPD, this effect is also known to be inconsistent. A 2002 meta-analysis showed that the person’s age at the time of their BCG vaccination and the years since vaccination influence the relative risk of a positive PPD (TABLE). The highest relative risk of a positive PPD occurred among patients who received BCG vaccination after infancy and within 15 years of the PPD testing. This same meta-analysis also examined the significance of the size of the PPD response; a subset of 4 studies showed that equal proportions of BCG vaccinated and unvaccinated patients had indurations of 14 mm or more.²

BCG vaccine may confound PPD readings, but several studies indicate that PPD can still be a useful screening tool for tuberculosis infection after vaccination. A Brazilian case-control study found that reactions by those BCG recipients later exposed to TB were significantly greater than those with no TB exposure.³ The study noted that 47.5% of exposed children (defined as those with a household contact) had PPD readings of >10 mm, compared with just 3.6% of control children. In a Quebec cohort of 1198 foreign-born children and young adults, prior BCG vaccination could account for 50% of PPDs with induration of 5 to 9 mm, but only 4% of reactions 10 mm or greater. This study also showed that patients from countries with a high or moderate incidence of TB were more likely to have reactive PPDs than those from countries of low incidence, suggesting that exposure to TB accounts for some of the positive PPDs.⁴

Where it is available, the QuantiFERON-TB Gold test may be used in place of, or in addition to, the PPD for patients who are known to have received a BCG vaccine. This blood test detects interferon-gamma in the serum of people sensitized to Mycobacterium tuberculosis. Because the test is specific to proteins found in M tuberculosis, there is no cross-reactivity with BCG. A Japanese study of 216 BCG-vaccinated individuals showed interferon-gamma assays to be 98.1% specific. The same study reported 89.0% sensitivity for the combination of 2 interferon-gamma assays among 118 TB culture-confirmed individuals.⁵ A published report estimated the cost to the health care system per patient tested by a single interferon-gamma release assay as $33.67, compared with approximately $11 for PPD testing.⁶

TABLE
PPD reactions >10 mm when BCG was given during and after infancy

Recommendations from others

While the US Preventive Services Task Force (USPSTF) does not make a specific recommendation regarding PPD readings after BCG vaccine, it does recommend screening high-risk populations. The USPSTF further notes that reactions >10 mm should not be attributed to prior BCG vaccine.⁷

The Centers for Disease Control and Prevention (CDC) and American Thoracic Society joint statement recommends against altering guidelines for testing and interpretation among BCG recipients.⁸ In 2005, the CDC recommended the QuantiFERON-TB Gold test be used under the same indications as the PPD, noting its potential benefit among those previously immunized with BCG.⁹