Cystic Fibrosis-Related Diabetes Is Not Your Typical Diabetes

BALTIMORE – Cystic fibrosis–related diabetes differs from type 1 and 2 diabetes and requires different management.

"Screening early and knowing which patients are at risk is really important," Amanda Leonard said at a meeting on pediatric nutrition sponsored by Johns Hopkins University.

Nutritional status and pulmonary function begin to decline in cystic fibrosis patients several years before diagnosis of cystic fibrosis–related diabetes (CFRD), so identifying and treating patients with CFRD can have a big impact on life expectancy, said Ms. Leonard, a senior pediatric clinical dietician at the Johns Hopkins Cystic Fibrosis Center.

Although CFRD is very different from type 1 and type 2 diabetes, "it does share some components," she said. She summarized the highlights of the clinical care guidelines for CFRD issued by the American Diabetes Association and the Cystic Fibrosis Foundation (Diabetes Care 2010;33:2697-708).

CFRD is associated with weight loss, protein catabolism, lung function decline, and increased mortality. There does not appear to be an autoimmune etiology for CFRD, and ketones are very rare.

For patients with cystic fibrosis, the incidence of related diabetes is more than 50% at age 40 years. The peak age of onset for CFRD is 20-24 years, whereas type 1 diabetes is more common in children and type 2 diabetes is more common in mid-to-late adulthood, she said.

"In CFRD there is a severe insulin deficiency, but it’s not as complete as in type 1," she said. CFRD is defined as the presence of at least two of the following on two occasions: a fasting glucose level of at least 126 mg/dL, a 2-hour oral glucose tolerance test (OGTT) of plasma glucose that is at least 200 mg/dL, or a hemoglobin A_1c of at least 6.5% (although an HbA_1c less than 6.5% does not exclude CFRD).

"Screening early and knowing which patients are at risk is really important."

In CFRD patients, fasting glucose can range from 100 to 125 mg/dL, and a 2-hour OGTT result can range from 140 to 199 mg/dL. "So it’s not quite diabetes, but it’s not quite right either," she said. CFRD is "not an all or nothing kind of thing. It’s not that either you have it or you don\'t. It can be transient in nature, and there’s a spectrum," she said.

An outpatient OGTT performed when the patient is clinically stable is the test of choice for routine screening. OGTT screening is recommended annually for cystic fibrosis patients who are not already known to have diabetes, and such screening should begin by the time the patient is 10 years old.

HbA_1c cannot be considered a screening test for CFRD because of the high prevalence of false negatives, but a low HbA_1c can be used to confirm diagnosis.

Hospitalized patients who are admitted for pulmonary exacerbation and/or treatment with corticosteroids should have both fasting and 2-hour postprandial blood glucose monitoring. CFRD is diagnosed when fasting or postprandial hyperglycemia persists longer than 48 hours.

Patients receiving overnight continuous drip feedings should have blood glucose monitoring midcycle to screen for CFRD. Diagnosis is based on a midcycle or immediate postfeeding glucose level of at least 200 mg/dL. This should be confirmed on two separate nights.

Insulin is the definitive treatment for all patients with CFRD (with or without fasting hyperglycemia). Other diabetes agents have not been shown to be of benefit in CFRD and cannot be recommended over insulin. "Insulin is the treatment of choice. Oral agents do not seem to work as well," Ms. Leonard said.

Blood glucose goals are the same as for all patients with diabetes but are adjusted for individual patient circumstances. In general, the HbA_1c goal is less than 7.0%.

Diet should be based on current guidelines for the nutritional management of all patients with cystic fibrosis. Counting carbohydrates to guide insulin therapy can help optimize glycemic control.

BALTIMORE – Cystic fibrosis–related diabetes differs from type 1 and 2 diabetes and requires different management.

"Screening early and knowing which patients are at risk is really important," Amanda Leonard said at a meeting on pediatric nutrition sponsored by Johns Hopkins University.

Nutritional status and pulmonary function begin to decline in cystic fibrosis patients several years before diagnosis of cystic fibrosis–related diabetes (CFRD), so identifying and treating patients with CFRD can have a big impact on life expectancy, said Ms. Leonard, a senior pediatric clinical dietician at the Johns Hopkins Cystic Fibrosis Center.

Although CFRD is very different from type 1 and type 2 diabetes, "it does share some components," she said. She summarized the highlights of the clinical care guidelines for CFRD issued by the American Diabetes Association and the Cystic Fibrosis Foundation (Diabetes Care 2010;33:2697-708).

CFRD is associated with weight loss, protein catabolism, lung function decline, and increased mortality. There does not appear to be an autoimmune etiology for CFRD, and ketones are very rare.

For patients with cystic fibrosis, the incidence of related diabetes is more than 50% at age 40 years. The peak age of onset for CFRD is 20-24 years, whereas type 1 diabetes is more common in children and type 2 diabetes is more common in mid-to-late adulthood, she said.

"In CFRD there is a severe insulin deficiency, but it’s not as complete as in type 1," she said. CFRD is defined as the presence of at least two of the following on two occasions: a fasting glucose level of at least 126 mg/dL, a 2-hour oral glucose tolerance test (OGTT) of plasma glucose that is at least 200 mg/dL, or a hemoglobin A_1c of at least 6.5% (although an HbA_1c less than 6.5% does not exclude CFRD).

"Screening early and knowing which patients are at risk is really important."

In CFRD patients, fasting glucose can range from 100 to 125 mg/dL, and a 2-hour OGTT result can range from 140 to 199 mg/dL. "So it’s not quite diabetes, but it’s not quite right either," she said. CFRD is "not an all or nothing kind of thing. It’s not that either you have it or you don\'t. It can be transient in nature, and there’s a spectrum," she said.

An outpatient OGTT performed when the patient is clinically stable is the test of choice for routine screening. OGTT screening is recommended annually for cystic fibrosis patients who are not already known to have diabetes, and such screening should begin by the time the patient is 10 years old.

HbA_1c cannot be considered a screening test for CFRD because of the high prevalence of false negatives, but a low HbA_1c can be used to confirm diagnosis.

Hospitalized patients who are admitted for pulmonary exacerbation and/or treatment with corticosteroids should have both fasting and 2-hour postprandial blood glucose monitoring. CFRD is diagnosed when fasting or postprandial hyperglycemia persists longer than 48 hours.

Patients receiving overnight continuous drip feedings should have blood glucose monitoring midcycle to screen for CFRD. Diagnosis is based on a midcycle or immediate postfeeding glucose level of at least 200 mg/dL. This should be confirmed on two separate nights.

Insulin is the definitive treatment for all patients with CFRD (with or without fasting hyperglycemia). Other diabetes agents have not been shown to be of benefit in CFRD and cannot be recommended over insulin. "Insulin is the treatment of choice. Oral agents do not seem to work as well," Ms. Leonard said.

Blood glucose goals are the same as for all patients with diabetes but are adjusted for individual patient circumstances. In general, the HbA_1c goal is less than 7.0%.

Diet should be based on current guidelines for the nutritional management of all patients with cystic fibrosis. Counting carbohydrates to guide insulin therapy can help optimize glycemic control.

BALTIMORE – Cystic fibrosis–related diabetes differs from type 1 and 2 diabetes and requires different management.

"Screening early and knowing which patients are at risk is really important," Amanda Leonard said at a meeting on pediatric nutrition sponsored by Johns Hopkins University.

Nutritional status and pulmonary function begin to decline in cystic fibrosis patients several years before diagnosis of cystic fibrosis–related diabetes (CFRD), so identifying and treating patients with CFRD can have a big impact on life expectancy, said Ms. Leonard, a senior pediatric clinical dietician at the Johns Hopkins Cystic Fibrosis Center.

Although CFRD is very different from type 1 and type 2 diabetes, "it does share some components," she said. She summarized the highlights of the clinical care guidelines for CFRD issued by the American Diabetes Association and the Cystic Fibrosis Foundation (Diabetes Care 2010;33:2697-708).

CFRD is associated with weight loss, protein catabolism, lung function decline, and increased mortality. There does not appear to be an autoimmune etiology for CFRD, and ketones are very rare.

For patients with cystic fibrosis, the incidence of related diabetes is more than 50% at age 40 years. The peak age of onset for CFRD is 20-24 years, whereas type 1 diabetes is more common in children and type 2 diabetes is more common in mid-to-late adulthood, she said.

"In CFRD there is a severe insulin deficiency, but it’s not as complete as in type 1," she said. CFRD is defined as the presence of at least two of the following on two occasions: a fasting glucose level of at least 126 mg/dL, a 2-hour oral glucose tolerance test (OGTT) of plasma glucose that is at least 200 mg/dL, or a hemoglobin A_1c of at least 6.5% (although an HbA_1c less than 6.5% does not exclude CFRD).

"Screening early and knowing which patients are at risk is really important."

In CFRD patients, fasting glucose can range from 100 to 125 mg/dL, and a 2-hour OGTT result can range from 140 to 199 mg/dL. "So it’s not quite diabetes, but it’s not quite right either," she said. CFRD is "not an all or nothing kind of thing. It’s not that either you have it or you don\'t. It can be transient in nature, and there’s a spectrum," she said.

An outpatient OGTT performed when the patient is clinically stable is the test of choice for routine screening. OGTT screening is recommended annually for cystic fibrosis patients who are not already known to have diabetes, and such screening should begin by the time the patient is 10 years old.

HbA_1c cannot be considered a screening test for CFRD because of the high prevalence of false negatives, but a low HbA_1c can be used to confirm diagnosis.

Hospitalized patients who are admitted for pulmonary exacerbation and/or treatment with corticosteroids should have both fasting and 2-hour postprandial blood glucose monitoring. CFRD is diagnosed when fasting or postprandial hyperglycemia persists longer than 48 hours.

Patients receiving overnight continuous drip feedings should have blood glucose monitoring midcycle to screen for CFRD. Diagnosis is based on a midcycle or immediate postfeeding glucose level of at least 200 mg/dL. This should be confirmed on two separate nights.

Insulin is the definitive treatment for all patients with CFRD (with or without fasting hyperglycemia). Other diabetes agents have not been shown to be of benefit in CFRD and cannot be recommended over insulin. "Insulin is the treatment of choice. Oral agents do not seem to work as well," Ms. Leonard said.

Blood glucose goals are the same as for all patients with diabetes but are adjusted for individual patient circumstances. In general, the HbA_1c goal is less than 7.0%.

Diet should be based on current guidelines for the nutritional management of all patients with cystic fibrosis. Counting carbohydrates to guide insulin therapy can help optimize glycemic control.