Background In children with cystic fibrosis (CF), cystic fibrosis related diabetes (CFRD) typically develops from adolescence onwards and coincides with deteriorating lung function. Currently, diagnosis of CFRD is based on WHO oral glucose tolerance test criteria rather than HbA1c (used as part of the diagnostic criteria for diabetes mellitus).

Objective To interrogate a national data set and determine prevalence of pre-diabetes and diabetes in patients not diagnosed with CFRD as based on HbA1c.

Methods A national CF data set (2007 to 2012) recording annual measurements of height, weight, BMI,%predicted FEV1 and FVC and HbA1c was interrogated. Young people up to the age of 23 years were included. HbA1c values between 5.7–6.5% and >6.5% were used to diagnose pre-diabetes and diabetes respectively in patients not labelled as having CFRD. Prevalence of pre-diabetes, diabetes and%FEV1 were determined by age group using the first visit values for each individual.

Results 3759 patients (1627 males, 87.5% with DF508 mutations), median (range) age 14.5 years (4.5–23 years), BMI Z score -0.17 (-5.7 +/- 3.6) were included. Prevalences of known CFRD, pre-diabetes and undiagnosed diabetes are shown in Table 1. In cross sectional analyses adjusted for gender, age, genotype and BMI, FEV1 was inversely associated with HbA1c, B=-5.0 (95% CI -6.0–3.0, p < 0.0001).

Conclusion In this large UK data set, an additional 6.6% of CF patients aged 16–23 years would be diagnosed with diabetes based on HbA1c values. Furthermore, the prevalence of undiagnosed pre-diabetes was high across all age groups and associated with lower %FEV1.