Association between HbA1c and the development of cystic fibrosis‐related diabetes

Aims To examine HbA1c as a predictor of risk for future development of cystic fibrosis‐related diabetes and to assess the association with the development of retinopathy in people with cystic fibrosis‐related diabetes. Methods A 7‐year retrospective longitudinal study was conducted in 50 adults with cystic fibrosis, comparing oral glucose tolerance test results with HbA1c values in predicting the development of cystic fibrosis‐related diabetes. Retinal screening data were also compared with HbA1c measurements to assess microvascular outcome. Results An HbA1c value ≥37 mmol/mol (5.5%; hazard ratio 3.49, CI 1.5–8.1) was significantly associated with the development of dysglycaemia, as defined by the oral glucose tolerance test over a 7‐year period. Severity of diabetic retinopathy was associated with a higher HbA1c and longer duration of cystic fibrosis‐related diabetes. Conclusion There is a link between HbA1c level and the future development of dysglycaemia in cystic fibrosis based on oral glucose tolerance test, as well as microvascular outcomes. Although current guidance does not advocate the use of HbA1c as a diagnostic tool in cystic fibrosis‐related diabetes, it may be of clinical use in determining individuals at risk of future development of cystic fibrosis‐related diabetes.