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Can low-dose aspirin prevent thromboembolic phenomena in patients undergoing surgery for hip fracture or elective arthroplasty?
BACKGROUND: Unfractionated and low-molecular-weight (LMW) heparins are popular and successful agents for preventing pulmonary embolism (PE) and deep vein thrombosis (DVT) after major surgery, but they are usually stopped at hospital discharge. The use of an antiplatelet agent such as low-dose aspirin might provide additional benefits. A meta-analysis of data from 8000 patients indicated several weeks of such therapy reduced the frequency of PE and DVT by 40% to 60%. The Pulmonary Embolism Prevention (PEP) trial of low-dose aspirin was a large randomized control trial (RCT) designed to confirm or refute these findings.
POPULATION STUDIED: This was a multicountry trial (Australia, New Zealand, South Africa, Sweden, and the United Kingdom) of patients with proximal femur fractures or undergoing hip or knee arthroplasty. Patients with a clear indication for aspirin (such as a recent myocardial infarction) or clear contraindication (such as an active peptic ulcer) were not eligible. Concurrent use of other thromboprophylactic agents and previous use of nonsteroidal anti-inflammatory drugs (NSAIDs) were allowed.
STUDY DESIGN AND VALIDITY: The PEP study was a double-blind placebo-controlled trial in which eligible patients who gave consent were randomly assigned to receive either 160 mg enteric-coated aspirin or placebo daily for 5 weeks, starting before surgery. The authors described the methods used to prevent researchers from knowing to which group the patient would be assigned (ie, concealed allocation). Patients were advised to avoid other NSAIDs during this time. A diagnosis of DVT required confirmation by venography or ultrasound; PEs were classified as definite or probable by an independent committee on the basis of a combination of clinical findings, angiogram, ventilation-perfusion scan, or venographic evidence of DVT. Follow-up assessed in-hospital morbidity and mortality and out-of-hospital mortality for the month following surgery. Analysis was by intention to treat. This was a large well-conducted trial involving at least 150 hospitals, with complete follow-up of 99.4% of enrollees. Randomization resulted in equal distribution on the basis of age and sex; no data on race or ethnicity were presented. The concurrent use of heparin agents was equally distributed between the intervention and control groups. Diagnosis of DVT, PE, MI, and cerebrovascular accident was made by a committee unaware of the subjects' group assignment.
OUTCOMES MEASURED: Follow-up was for cause of death through day 35 and for nonfatal events during the hospitalization (mean duration=16 days).
RESULTS: Approximately 13,000 patients with hip fracture were randomized, with 92% initiating treatment preoperatively or immediately postoperatively and 80% taking the assigned medication for the entire 35-day follow-up. Approximately 45% of the participants were receiving a form of heparin (similar numbers in both groups). Symptomatic DVT was confirmed in 1.03% of those assigned aspirin and 1.45% of those assigned placebo (P=.03; number needed to treat [NNT]=238). Definite or probable PE was confirmed in 0.69% of patients taking aspirin and 1.21% of those taking placebo (P=.002; NNT=192). For fatal PE, the NNT was 270 (P=.002). The overall mortality was identical in both groups. Aspirin had statistically significant benefits on total thromboembolic events in those patients taking unfractionated heparin or no heparin but not in those who received LMW heparin. Nonfatal and fatal cardiac ischemic events occurred more frequently in the aspirin group (1.57% vs 1.18%, P=.05). A total of 256 patients would need to receive aspirin for one additional event to occur (number needed to harm [NNH]=256). Fatal bleeding episodes were approximately equal in both groups; however, 2.95% of the patients assigned to aspirin required transfusion versus 2.35% of patients assigned to placebo (P=.04; NNH=167). The number of patients in the arthroplasty section of the trial was smaller (n=4000), and none of the comparisons between the intervention and placebo groups showed statistically significant results.
This well-designed RCT, mainly of patients with hip fractures, shows the incidence of thromboembolic events to be quite low in the first 5 weeks after injury. The addition of low-dose aspirin to these patients' treatment significantly reduced the incidence of DVT and PE, but large numbers need to be treated to realize any benefit (NNT=approximately 200 for nonfatal events and 270 for fatal events), and there was no effect on overall mortality. The aspirin group also had significantly more bleeding complications requiring transfusions and a higher incidence of fatal and nonfatal ischemic heart disease events. Despite aspirin's low cost and ease of use, the benefits of its perioperative use for 35 days in patients with new hip fractures are small, and the rate of complications from its use almost balance its benefits. The increased use of other thromboprophylactic treatments (various forms of heparin and pressure stockings) probably made it difficult for aspirin to produce a marked additional effect that would lower an already low rate of adverse events.
BACKGROUND: Unfractionated and low-molecular-weight (LMW) heparins are popular and successful agents for preventing pulmonary embolism (PE) and deep vein thrombosis (DVT) after major surgery, but they are usually stopped at hospital discharge. The use of an antiplatelet agent such as low-dose aspirin might provide additional benefits. A meta-analysis of data from 8000 patients indicated several weeks of such therapy reduced the frequency of PE and DVT by 40% to 60%. The Pulmonary Embolism Prevention (PEP) trial of low-dose aspirin was a large randomized control trial (RCT) designed to confirm or refute these findings.
POPULATION STUDIED: This was a multicountry trial (Australia, New Zealand, South Africa, Sweden, and the United Kingdom) of patients with proximal femur fractures or undergoing hip or knee arthroplasty. Patients with a clear indication for aspirin (such as a recent myocardial infarction) or clear contraindication (such as an active peptic ulcer) were not eligible. Concurrent use of other thromboprophylactic agents and previous use of nonsteroidal anti-inflammatory drugs (NSAIDs) were allowed.
STUDY DESIGN AND VALIDITY: The PEP study was a double-blind placebo-controlled trial in which eligible patients who gave consent were randomly assigned to receive either 160 mg enteric-coated aspirin or placebo daily for 5 weeks, starting before surgery. The authors described the methods used to prevent researchers from knowing to which group the patient would be assigned (ie, concealed allocation). Patients were advised to avoid other NSAIDs during this time. A diagnosis of DVT required confirmation by venography or ultrasound; PEs were classified as definite or probable by an independent committee on the basis of a combination of clinical findings, angiogram, ventilation-perfusion scan, or venographic evidence of DVT. Follow-up assessed in-hospital morbidity and mortality and out-of-hospital mortality for the month following surgery. Analysis was by intention to treat. This was a large well-conducted trial involving at least 150 hospitals, with complete follow-up of 99.4% of enrollees. Randomization resulted in equal distribution on the basis of age and sex; no data on race or ethnicity were presented. The concurrent use of heparin agents was equally distributed between the intervention and control groups. Diagnosis of DVT, PE, MI, and cerebrovascular accident was made by a committee unaware of the subjects' group assignment.
OUTCOMES MEASURED: Follow-up was for cause of death through day 35 and for nonfatal events during the hospitalization (mean duration=16 days).
RESULTS: Approximately 13,000 patients with hip fracture were randomized, with 92% initiating treatment preoperatively or immediately postoperatively and 80% taking the assigned medication for the entire 35-day follow-up. Approximately 45% of the participants were receiving a form of heparin (similar numbers in both groups). Symptomatic DVT was confirmed in 1.03% of those assigned aspirin and 1.45% of those assigned placebo (P=.03; number needed to treat [NNT]=238). Definite or probable PE was confirmed in 0.69% of patients taking aspirin and 1.21% of those taking placebo (P=.002; NNT=192). For fatal PE, the NNT was 270 (P=.002). The overall mortality was identical in both groups. Aspirin had statistically significant benefits on total thromboembolic events in those patients taking unfractionated heparin or no heparin but not in those who received LMW heparin. Nonfatal and fatal cardiac ischemic events occurred more frequently in the aspirin group (1.57% vs 1.18%, P=.05). A total of 256 patients would need to receive aspirin for one additional event to occur (number needed to harm [NNH]=256). Fatal bleeding episodes were approximately equal in both groups; however, 2.95% of the patients assigned to aspirin required transfusion versus 2.35% of patients assigned to placebo (P=.04; NNH=167). The number of patients in the arthroplasty section of the trial was smaller (n=4000), and none of the comparisons between the intervention and placebo groups showed statistically significant results.
This well-designed RCT, mainly of patients with hip fractures, shows the incidence of thromboembolic events to be quite low in the first 5 weeks after injury. The addition of low-dose aspirin to these patients' treatment significantly reduced the incidence of DVT and PE, but large numbers need to be treated to realize any benefit (NNT=approximately 200 for nonfatal events and 270 for fatal events), and there was no effect on overall mortality. The aspirin group also had significantly more bleeding complications requiring transfusions and a higher incidence of fatal and nonfatal ischemic heart disease events. Despite aspirin's low cost and ease of use, the benefits of its perioperative use for 35 days in patients with new hip fractures are small, and the rate of complications from its use almost balance its benefits. The increased use of other thromboprophylactic treatments (various forms of heparin and pressure stockings) probably made it difficult for aspirin to produce a marked additional effect that would lower an already low rate of adverse events.
BACKGROUND: Unfractionated and low-molecular-weight (LMW) heparins are popular and successful agents for preventing pulmonary embolism (PE) and deep vein thrombosis (DVT) after major surgery, but they are usually stopped at hospital discharge. The use of an antiplatelet agent such as low-dose aspirin might provide additional benefits. A meta-analysis of data from 8000 patients indicated several weeks of such therapy reduced the frequency of PE and DVT by 40% to 60%. The Pulmonary Embolism Prevention (PEP) trial of low-dose aspirin was a large randomized control trial (RCT) designed to confirm or refute these findings.
POPULATION STUDIED: This was a multicountry trial (Australia, New Zealand, South Africa, Sweden, and the United Kingdom) of patients with proximal femur fractures or undergoing hip or knee arthroplasty. Patients with a clear indication for aspirin (such as a recent myocardial infarction) or clear contraindication (such as an active peptic ulcer) were not eligible. Concurrent use of other thromboprophylactic agents and previous use of nonsteroidal anti-inflammatory drugs (NSAIDs) were allowed.
STUDY DESIGN AND VALIDITY: The PEP study was a double-blind placebo-controlled trial in which eligible patients who gave consent were randomly assigned to receive either 160 mg enteric-coated aspirin or placebo daily for 5 weeks, starting before surgery. The authors described the methods used to prevent researchers from knowing to which group the patient would be assigned (ie, concealed allocation). Patients were advised to avoid other NSAIDs during this time. A diagnosis of DVT required confirmation by venography or ultrasound; PEs were classified as definite or probable by an independent committee on the basis of a combination of clinical findings, angiogram, ventilation-perfusion scan, or venographic evidence of DVT. Follow-up assessed in-hospital morbidity and mortality and out-of-hospital mortality for the month following surgery. Analysis was by intention to treat. This was a large well-conducted trial involving at least 150 hospitals, with complete follow-up of 99.4% of enrollees. Randomization resulted in equal distribution on the basis of age and sex; no data on race or ethnicity were presented. The concurrent use of heparin agents was equally distributed between the intervention and control groups. Diagnosis of DVT, PE, MI, and cerebrovascular accident was made by a committee unaware of the subjects' group assignment.
OUTCOMES MEASURED: Follow-up was for cause of death through day 35 and for nonfatal events during the hospitalization (mean duration=16 days).
RESULTS: Approximately 13,000 patients with hip fracture were randomized, with 92% initiating treatment preoperatively or immediately postoperatively and 80% taking the assigned medication for the entire 35-day follow-up. Approximately 45% of the participants were receiving a form of heparin (similar numbers in both groups). Symptomatic DVT was confirmed in 1.03% of those assigned aspirin and 1.45% of those assigned placebo (P=.03; number needed to treat [NNT]=238). Definite or probable PE was confirmed in 0.69% of patients taking aspirin and 1.21% of those taking placebo (P=.002; NNT=192). For fatal PE, the NNT was 270 (P=.002). The overall mortality was identical in both groups. Aspirin had statistically significant benefits on total thromboembolic events in those patients taking unfractionated heparin or no heparin but not in those who received LMW heparin. Nonfatal and fatal cardiac ischemic events occurred more frequently in the aspirin group (1.57% vs 1.18%, P=.05). A total of 256 patients would need to receive aspirin for one additional event to occur (number needed to harm [NNH]=256). Fatal bleeding episodes were approximately equal in both groups; however, 2.95% of the patients assigned to aspirin required transfusion versus 2.35% of patients assigned to placebo (P=.04; NNH=167). The number of patients in the arthroplasty section of the trial was smaller (n=4000), and none of the comparisons between the intervention and placebo groups showed statistically significant results.
This well-designed RCT, mainly of patients with hip fractures, shows the incidence of thromboembolic events to be quite low in the first 5 weeks after injury. The addition of low-dose aspirin to these patients' treatment significantly reduced the incidence of DVT and PE, but large numbers need to be treated to realize any benefit (NNT=approximately 200 for nonfatal events and 270 for fatal events), and there was no effect on overall mortality. The aspirin group also had significantly more bleeding complications requiring transfusions and a higher incidence of fatal and nonfatal ischemic heart disease events. Despite aspirin's low cost and ease of use, the benefits of its perioperative use for 35 days in patients with new hip fractures are small, and the rate of complications from its use almost balance its benefits. The increased use of other thromboprophylactic treatments (various forms of heparin and pressure stockings) probably made it difficult for aspirin to produce a marked additional effect that would lower an already low rate of adverse events.
In patients with stable persistent asthma, can lower doses of inhaled corticosteroid medication control symptoms and maintain optimal pulmonary function as well as high doses?
BACKGROUND: In patients with chronic asthma, inflammation caused by numerous stimuli leads to recurrent symptoms, variable airflow obstruction, and bronchial hyperresponsiveness. Effective long-term control of persistent asthma requires daily administration of an anti-inflammatory agent, preferably an inhaled corticosteroid. Although inhaled steroids are generally well tolerated and safe, the lowest effective dose should be used to reduce the potential for adverse effects.1
POPULATION STUDIED: The investigators enrolled 220 adult patients with perennial asthma from 14 outpatient clinics in Italy. Patients in this study had to be using an inhaled corticosteroid and an inhaled b2-agonist daily, had a baseline forced expiratory volume in 1 second between 50% and 90% predicted, and had symptoms present that interfered with normal daily activity during the previous 2 weeks. Patients were not included if they required systemic corticosteroids within the past month or used more than 1000 μg per day of inhaled beclomethasone dipropionate.
STUDY DESIGN AND VALIDITY: The appropriate study design was used for this article about therapy. It was a prospective randomized double-blind trial funded by the manufacturer of budesonide (available in the United States as Pulmicort). Following a 2-week observation period to establish asthma severity, all patients were treated with high-dose (800 μg twice daily) inhaled budesonide for 1 month. Patients were then randomized to receive either 400 μg (standard dose) or 100 μg (low dose) of budesonide twice daily for 6 months. The high-dose group received a placebo inhaler for use during exacerbations. The low-dose group was further divided to receive either a placebo inhaler or budesonide 200 μg 4 times daily during exacerbations. Exacerbations were identified using daily peak flow measurements to trigger the short-term use of either higher doses of inhaled budesonide or the placebo inhaler. Patients were assessed monthly and were asked to maintain a daily record of asthma symptoms, exacerbations, peak flow values, and use of b2-agonists. The patients and those assessing response to therapy were not aware of the budesonide dose. Concealed allocation to treatment group at each study site was assured through central randomization. Eighty percent of the enrolled patients completed the study, and all withdrawals were explained. Only adults (18 years and older) were studied, and the results may not be applicable to children.
OUTCOMES MEASURED: Both patient-oriented outcomes (symptom control and number of exacerbations) and disease-oriented outcomes (pulmonary function) were used to assess treatment response.
RESULTS: Of 220 enrolled patients, 213 were randomized to different doses of budesonide. The results for 209 of these (4 withdrew just after randomization) were analyzed appropriately by intention to treat. Treatment groups were well matched demographically and for confounding factors that might influence response to treatment. All patients responded well to the 4 weeks of high-dose therapy, showing progressive improvement in pulmonary function, with the majority reporting no symptoms at the end of the month. Standard-dose and low-dose budesonide controlled symptoms equally throughout the study, with no statistically significant differences reported for any symptom. Patients receiving standard-dose budesonide experienced fewer exacerbations than those receiving low-dose therapy. However, low-dose therapy patients using increased budesonide doses during exacerbations experienced significantly fewer exacerbations and fewer days of worsened symptoms than those continuing on low doses. The low-dose group using as-needed higher doses did not differ from the standard-dose group with respect to the number of days with exacerbations.
For adults with chronic asthma, a regimen of low-dose inhaled budesonide plus higher doses during exacerbations was as effective as continuous standard doses for controlling symptoms and minimizing exacerbations. For patients willing to perform daily peak flow monitoring to allow early treatment of mild exacerbations with increased doses of inhaled corticosteroid medication, this approach can result in good long-term asthma control with lower doses of inhaled corticosteroids.
BACKGROUND: In patients with chronic asthma, inflammation caused by numerous stimuli leads to recurrent symptoms, variable airflow obstruction, and bronchial hyperresponsiveness. Effective long-term control of persistent asthma requires daily administration of an anti-inflammatory agent, preferably an inhaled corticosteroid. Although inhaled steroids are generally well tolerated and safe, the lowest effective dose should be used to reduce the potential for adverse effects.1
POPULATION STUDIED: The investigators enrolled 220 adult patients with perennial asthma from 14 outpatient clinics in Italy. Patients in this study had to be using an inhaled corticosteroid and an inhaled b2-agonist daily, had a baseline forced expiratory volume in 1 second between 50% and 90% predicted, and had symptoms present that interfered with normal daily activity during the previous 2 weeks. Patients were not included if they required systemic corticosteroids within the past month or used more than 1000 μg per day of inhaled beclomethasone dipropionate.
STUDY DESIGN AND VALIDITY: The appropriate study design was used for this article about therapy. It was a prospective randomized double-blind trial funded by the manufacturer of budesonide (available in the United States as Pulmicort). Following a 2-week observation period to establish asthma severity, all patients were treated with high-dose (800 μg twice daily) inhaled budesonide for 1 month. Patients were then randomized to receive either 400 μg (standard dose) or 100 μg (low dose) of budesonide twice daily for 6 months. The high-dose group received a placebo inhaler for use during exacerbations. The low-dose group was further divided to receive either a placebo inhaler or budesonide 200 μg 4 times daily during exacerbations. Exacerbations were identified using daily peak flow measurements to trigger the short-term use of either higher doses of inhaled budesonide or the placebo inhaler. Patients were assessed monthly and were asked to maintain a daily record of asthma symptoms, exacerbations, peak flow values, and use of b2-agonists. The patients and those assessing response to therapy were not aware of the budesonide dose. Concealed allocation to treatment group at each study site was assured through central randomization. Eighty percent of the enrolled patients completed the study, and all withdrawals were explained. Only adults (18 years and older) were studied, and the results may not be applicable to children.
OUTCOMES MEASURED: Both patient-oriented outcomes (symptom control and number of exacerbations) and disease-oriented outcomes (pulmonary function) were used to assess treatment response.
RESULTS: Of 220 enrolled patients, 213 were randomized to different doses of budesonide. The results for 209 of these (4 withdrew just after randomization) were analyzed appropriately by intention to treat. Treatment groups were well matched demographically and for confounding factors that might influence response to treatment. All patients responded well to the 4 weeks of high-dose therapy, showing progressive improvement in pulmonary function, with the majority reporting no symptoms at the end of the month. Standard-dose and low-dose budesonide controlled symptoms equally throughout the study, with no statistically significant differences reported for any symptom. Patients receiving standard-dose budesonide experienced fewer exacerbations than those receiving low-dose therapy. However, low-dose therapy patients using increased budesonide doses during exacerbations experienced significantly fewer exacerbations and fewer days of worsened symptoms than those continuing on low doses. The low-dose group using as-needed higher doses did not differ from the standard-dose group with respect to the number of days with exacerbations.
For adults with chronic asthma, a regimen of low-dose inhaled budesonide plus higher doses during exacerbations was as effective as continuous standard doses for controlling symptoms and minimizing exacerbations. For patients willing to perform daily peak flow monitoring to allow early treatment of mild exacerbations with increased doses of inhaled corticosteroid medication, this approach can result in good long-term asthma control with lower doses of inhaled corticosteroids.
BACKGROUND: In patients with chronic asthma, inflammation caused by numerous stimuli leads to recurrent symptoms, variable airflow obstruction, and bronchial hyperresponsiveness. Effective long-term control of persistent asthma requires daily administration of an anti-inflammatory agent, preferably an inhaled corticosteroid. Although inhaled steroids are generally well tolerated and safe, the lowest effective dose should be used to reduce the potential for adverse effects.1
POPULATION STUDIED: The investigators enrolled 220 adult patients with perennial asthma from 14 outpatient clinics in Italy. Patients in this study had to be using an inhaled corticosteroid and an inhaled b2-agonist daily, had a baseline forced expiratory volume in 1 second between 50% and 90% predicted, and had symptoms present that interfered with normal daily activity during the previous 2 weeks. Patients were not included if they required systemic corticosteroids within the past month or used more than 1000 μg per day of inhaled beclomethasone dipropionate.
STUDY DESIGN AND VALIDITY: The appropriate study design was used for this article about therapy. It was a prospective randomized double-blind trial funded by the manufacturer of budesonide (available in the United States as Pulmicort). Following a 2-week observation period to establish asthma severity, all patients were treated with high-dose (800 μg twice daily) inhaled budesonide for 1 month. Patients were then randomized to receive either 400 μg (standard dose) or 100 μg (low dose) of budesonide twice daily for 6 months. The high-dose group received a placebo inhaler for use during exacerbations. The low-dose group was further divided to receive either a placebo inhaler or budesonide 200 μg 4 times daily during exacerbations. Exacerbations were identified using daily peak flow measurements to trigger the short-term use of either higher doses of inhaled budesonide or the placebo inhaler. Patients were assessed monthly and were asked to maintain a daily record of asthma symptoms, exacerbations, peak flow values, and use of b2-agonists. The patients and those assessing response to therapy were not aware of the budesonide dose. Concealed allocation to treatment group at each study site was assured through central randomization. Eighty percent of the enrolled patients completed the study, and all withdrawals were explained. Only adults (18 years and older) were studied, and the results may not be applicable to children.
OUTCOMES MEASURED: Both patient-oriented outcomes (symptom control and number of exacerbations) and disease-oriented outcomes (pulmonary function) were used to assess treatment response.
RESULTS: Of 220 enrolled patients, 213 were randomized to different doses of budesonide. The results for 209 of these (4 withdrew just after randomization) were analyzed appropriately by intention to treat. Treatment groups were well matched demographically and for confounding factors that might influence response to treatment. All patients responded well to the 4 weeks of high-dose therapy, showing progressive improvement in pulmonary function, with the majority reporting no symptoms at the end of the month. Standard-dose and low-dose budesonide controlled symptoms equally throughout the study, with no statistically significant differences reported for any symptom. Patients receiving standard-dose budesonide experienced fewer exacerbations than those receiving low-dose therapy. However, low-dose therapy patients using increased budesonide doses during exacerbations experienced significantly fewer exacerbations and fewer days of worsened symptoms than those continuing on low doses. The low-dose group using as-needed higher doses did not differ from the standard-dose group with respect to the number of days with exacerbations.
For adults with chronic asthma, a regimen of low-dose inhaled budesonide plus higher doses during exacerbations was as effective as continuous standard doses for controlling symptoms and minimizing exacerbations. For patients willing to perform daily peak flow monitoring to allow early treatment of mild exacerbations with increased doses of inhaled corticosteroid medication, this approach can result in good long-term asthma control with lower doses of inhaled corticosteroids.
Is spiral (helical) computed tomography useful for diagnosing pulmonary embolism?
BACKGROUND: An estimated 175,000 Americans have a pulmonary embolism (PE) each year. Pulmonary angiography is the accepted gold standard for diagnosing PE, but it is invasive, expensive, and causes cardiopulmonary complications in 3% to 4% of patients. A ventilation-perfusion (V/Q) scan is less invasive, but also less accurate. Used in combination with clinical assessment, it fails to find 20% of PEs.1 Recent studies evaluating the use of spiral computed tomography (CT) have reported favorable results in diagnosing PE. However, the role of CT for this use is not yet fully defined.
POPULATION STUDIED: In this systematic review, neither specific patient characteristics nor exclusion criteria were mentioned. Enrollment criteria were described as inconsistent.
STUDY DESIGN AND VALIDITY: The authors conducted a systematic review of the literature evaluating the use of spiral CT in diagnosing PE. They searched MEDLINE and Current Contents through July 1998 and reviewed pertinent references. Eleven articles met their preset inclusion criteria. The articles were rated by using a set of 11 basic methodologic standards for addressing diagnostic test research. None of the 11 studies met all of the criteria; only 5 studies met 5 or more criteria. All studies compared CT with either pulmonary angiography or another reference standard (high-probability V/Q scan plus high clinical suspicion) to confirm the diagnosis of PE. The studies were not methodologically similar enough to perform a meta-analysis.
OUTCOMES MEASURED: The primary outcome was the presence of a PE.
RESULTS: Compared with the gold standard of pulmonary angiography, the sensitivity of spiral CT ranged from 64% to 93%. If a PE is present, the probability of a positive CT scan is 64% to 93%. That means up to one third of PEs could be missed. The reported specificity ranged from 89% to 100%, which corresponds to a false-positive rate of 0% to 11%. These results are similar to those of another recent systematic review in which the authors reported a sensitivity range of 53% to 100% and a specificity range of 81% to 100%.1 Nine of the studies differentiated between large central and small subsegmental vessel embolism. When stratified by site, the sensitivity for spiral CT was much higher for central vessel PE (83% to 100%) than for subsegmental vessel PE (29%).
A review of the current available literature does not support the use of spiral CT for diagnosing PE. Although it appears that CT is better for identifying larger vessel PEs, the high false-negative rate prohibits its routine use as a rule-out test. In addition, many of the currently available studies employ methods that do not answer questions about the role and cost-effectiveness of spiral CT. More information is needed before we can recommend the routine use of spiral CT for the diagnosis of PE in clinical practice.
BACKGROUND: An estimated 175,000 Americans have a pulmonary embolism (PE) each year. Pulmonary angiography is the accepted gold standard for diagnosing PE, but it is invasive, expensive, and causes cardiopulmonary complications in 3% to 4% of patients. A ventilation-perfusion (V/Q) scan is less invasive, but also less accurate. Used in combination with clinical assessment, it fails to find 20% of PEs.1 Recent studies evaluating the use of spiral computed tomography (CT) have reported favorable results in diagnosing PE. However, the role of CT for this use is not yet fully defined.
POPULATION STUDIED: In this systematic review, neither specific patient characteristics nor exclusion criteria were mentioned. Enrollment criteria were described as inconsistent.
STUDY DESIGN AND VALIDITY: The authors conducted a systematic review of the literature evaluating the use of spiral CT in diagnosing PE. They searched MEDLINE and Current Contents through July 1998 and reviewed pertinent references. Eleven articles met their preset inclusion criteria. The articles were rated by using a set of 11 basic methodologic standards for addressing diagnostic test research. None of the 11 studies met all of the criteria; only 5 studies met 5 or more criteria. All studies compared CT with either pulmonary angiography or another reference standard (high-probability V/Q scan plus high clinical suspicion) to confirm the diagnosis of PE. The studies were not methodologically similar enough to perform a meta-analysis.
OUTCOMES MEASURED: The primary outcome was the presence of a PE.
RESULTS: Compared with the gold standard of pulmonary angiography, the sensitivity of spiral CT ranged from 64% to 93%. If a PE is present, the probability of a positive CT scan is 64% to 93%. That means up to one third of PEs could be missed. The reported specificity ranged from 89% to 100%, which corresponds to a false-positive rate of 0% to 11%. These results are similar to those of another recent systematic review in which the authors reported a sensitivity range of 53% to 100% and a specificity range of 81% to 100%.1 Nine of the studies differentiated between large central and small subsegmental vessel embolism. When stratified by site, the sensitivity for spiral CT was much higher for central vessel PE (83% to 100%) than for subsegmental vessel PE (29%).
A review of the current available literature does not support the use of spiral CT for diagnosing PE. Although it appears that CT is better for identifying larger vessel PEs, the high false-negative rate prohibits its routine use as a rule-out test. In addition, many of the currently available studies employ methods that do not answer questions about the role and cost-effectiveness of spiral CT. More information is needed before we can recommend the routine use of spiral CT for the diagnosis of PE in clinical practice.
BACKGROUND: An estimated 175,000 Americans have a pulmonary embolism (PE) each year. Pulmonary angiography is the accepted gold standard for diagnosing PE, but it is invasive, expensive, and causes cardiopulmonary complications in 3% to 4% of patients. A ventilation-perfusion (V/Q) scan is less invasive, but also less accurate. Used in combination with clinical assessment, it fails to find 20% of PEs.1 Recent studies evaluating the use of spiral computed tomography (CT) have reported favorable results in diagnosing PE. However, the role of CT for this use is not yet fully defined.
POPULATION STUDIED: In this systematic review, neither specific patient characteristics nor exclusion criteria were mentioned. Enrollment criteria were described as inconsistent.
STUDY DESIGN AND VALIDITY: The authors conducted a systematic review of the literature evaluating the use of spiral CT in diagnosing PE. They searched MEDLINE and Current Contents through July 1998 and reviewed pertinent references. Eleven articles met their preset inclusion criteria. The articles were rated by using a set of 11 basic methodologic standards for addressing diagnostic test research. None of the 11 studies met all of the criteria; only 5 studies met 5 or more criteria. All studies compared CT with either pulmonary angiography or another reference standard (high-probability V/Q scan plus high clinical suspicion) to confirm the diagnosis of PE. The studies were not methodologically similar enough to perform a meta-analysis.
OUTCOMES MEASURED: The primary outcome was the presence of a PE.
RESULTS: Compared with the gold standard of pulmonary angiography, the sensitivity of spiral CT ranged from 64% to 93%. If a PE is present, the probability of a positive CT scan is 64% to 93%. That means up to one third of PEs could be missed. The reported specificity ranged from 89% to 100%, which corresponds to a false-positive rate of 0% to 11%. These results are similar to those of another recent systematic review in which the authors reported a sensitivity range of 53% to 100% and a specificity range of 81% to 100%.1 Nine of the studies differentiated between large central and small subsegmental vessel embolism. When stratified by site, the sensitivity for spiral CT was much higher for central vessel PE (83% to 100%) than for subsegmental vessel PE (29%).
A review of the current available literature does not support the use of spiral CT for diagnosing PE. Although it appears that CT is better for identifying larger vessel PEs, the high false-negative rate prohibits its routine use as a rule-out test. In addition, many of the currently available studies employ methods that do not answer questions about the role and cost-effectiveness of spiral CT. More information is needed before we can recommend the routine use of spiral CT for the diagnosis of PE in clinical practice.