Cystic Fibrosis - Insulin Deficiency, Early Action

As well as progressive lung disease, patients with Cystic Fibrosis (CF) suffer pancreatic destruction, leading to slow but progressive insulin deficiency. Deficiency of insulin, a powerful anabolic hormone, causes accelerated decline of weight and lung function (important predictors of early mortality in CF).

We analysed Oral Glucose Tolerance Tests sampled every 30 mins and defined stages of CF Insulin Deficiency (CFID) as early glucose abnormalities, CFID1 (BGmax >=8.2 and <11.1mmol/L) and CFID2 (BGmax >=11.1 and BG120min <11.1), progressing to diabetes without fasting hyperglycaemia (CFID3), and finally to diabetes with fasting hyperglycaemia (CFID4). Currently insulin treatment is standard only for CFID3 and 4, but we have data showing that the earlier stages (CFID1 and 2) are also associated with declining weight and lung function.

In the CF-IDEA Trial, subjects with CF aged >=5 years with early glucose abnormalities (CFID1 or 2) will be randomised to once-daily insulin detemir (Levemir) for 12 months, or to observation only. We aim to determine whether starting insulin earlier than current practice will prevent decline in weight and lung function, reduce frequency of hospitalisation, improve quality of life, and slow progression through CFID categories.

Our pilot studies using once-daily Levemir in children with CFID1 and 2 found that this simple insulin regimen (rather than multiple daily injections) was well accepted by patients, with minimal hypoglycaemia, and resulted in significant weight gain and improved lung function (compared with 12 months prior to insulin). Sample size calculations for the CF-IDEA Trial are based on our pilot studies. When 70-80% of patients have completed the protocol, the study statistician will perform an interim analysis (blinded to the other investigators) to check the original power calculations.

Stages of CF Insulin Deficiency:

CFID1 Peak BG on OGTT >=8.2mmol/L and <11.1mmol/l.

CFID2 Peak BG on OGTT >=11.1mmol/L and 120 minute BG <11.1.

CFID3 120 minute BG on OGTT >=11.1mmol/L.

CFID4 Fasting hyperglycemia (Fasting BG >=7mmol/L).

Inclusion criteria

• Patients with CF aged >=5 yrs attending one of the study sites.
• CFID1 or CFID2 (defined as BGmax >=8.2 and BG120 <11.1mmol/l on OGTT performed within the last 6 months, when respiratory function stable as judged by the treating respiratory team, not taking fluoroquinolone antibiotics, and not taking systemic glucocorticoids).

Exclusion criteria

• Cystic Fibrosis Related Diabetes, defined as CFID3 (BG120 >11.1mmol/L) or CFID4 (fasting BG >7mmol/L). Such patients will be offered insulin treatment as standard clinical care.
• Unstable respiratory disease (hospital admission for treatment of respiratory exacerbation within the last month).
• Treatment with systemic glucocorticoids of more than 1 month duration, within the last 12 months.