Objectives To interrogate the UK national data set and explore longitudinal relationships between FEV1, HbA1c and OGTT parameters in young people with CF up to the age of 23 years.

Methods The UK CF data set (2007 to 2012) recording annual measurements of height, weight, BMI,% predicted FEV1 and FVC, HbA1c and 2 h glucose (2 hrGlu) (>10 years only) was interrogated. HbA1c values >6.5% and 5.7–6.5% were used to define ‘undiagnosed’ diabetes and a pre-diabetic state respectively in patients not labelled as having CFRD. Data from cases with known CFRD were censored. Longitudinal models analysed%FEV1 and %FVC as dependent variables and HbA1c or 2 hrGlu, BMI SDS and age as covariates in patients with HbA1c in the pre-diabetic range.

Results 2105 patients (1097 males), 87.9% with DF508 mutations, median (range) age 13.7 (5.6–22) years, mean (SD) BMI Z score -0.11+/-1.1, %FEV1 82.1+/-20.3 at first visit were included. Median range follow up was 3 (1–5) years. 2 hrGlu was available in a subgroup (n = 636). Median HbA1c (Table 1) but not 2 hrGlu (slope -0.1, p = 0.3), within the pre-diabetic range (5.7–6.5%) were inversely associated with %FEV1.

Conclusion In this large UK data set, longitudinal increases in HbA1c within the pre-diabetic range were associated with declining lung function. Our findings support the rationale for trials to invervene early to manage hyperglycaemia in young CF patients with pre-diabetes.