Insulin therapy is recommended by the Cystic Fibrosis Foundation when cystic fibrosis-related diabetes has been diagnosed. Diagnosis is based on an elevated fasting blood glucose level greater than 6.94 mmol/liter (125 mg/deciliter) or symptomatic diabetes for random glucose levels greater than 11.11 mmol/liter (200 mg/deciliter).
To examine the evidence that, when treated with agents for managing diabetes, people with cystic fibrosis improve their sugar metabolic control resulting in beneficial impact on lung function and the ability to maintain optimal weight.
We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.
We also handsearched abstracts from pulmonary and North American Cystic Fibrosis Conference symposia.
Date of the most recent search of the Group's Trials Register: April 2008.
Randomized controlled trials comparing all methods of diabetes therapy in people with cystic fibrosis.
Data collection and analysis
Two authors independently extracted data and assessed the risk of bias from the single included study.
Twenty references to fourteen studies were identified by the searches. One study (seven participants) comparing insulin with oral repaglinide has been included. We were unable to present the data graphically as they had been more appropriately reported in the primary paper, which states that at the doses given (not comparable), insulin was more beneficial than repaglinide to people with cystic fibrosis-related diabetes. Three incidences of hypoglycemia (two in the insulin group and one in the repaglinide group) were reported, all occurring an average of four hours after the test meal and resolved without further treatment.
While some cystic fibrosis centers use oral medications to help control diabetes, insulin therapy is the recommended and most widely used treatment method. This systematic review to date only identifies one short-term (five-hour) study, with little clinical relevance relating to the poor long-term prognosis recognized for cystic fibrosis-related diabetes. The need for a multicentre randomized controlled trial assessing both the efficacy of insulin or other insulin-releasing or insulin-sensitizing medications and their possible adverse effects in managing cystic fibrosis-related diabetes and which relates more realistically to long-term glycemic control continues to be a priority.