Association between HbA_1c and the development of cystic fibrosis‐related diabetes

Abstract

Aims To examine HbA 1c 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 HbA 1c values in predicting the development of cystic fibrosis-related diabetes. Retinal screening data were also compared with HbA 1c measurements to assess microvascular outcome.Results An HbA 1c 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 HbA 1c and longer duration of cystic fibrosis-related diabetes.Conclusion There is a link between HbA 1c 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 HbA 1c 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.

Learning about diabetes through epidemiology

“…In a study of 50 adults with cystic fibrosis, however, Choudhury et al . show that HbA 1c had a higher area under the receiver‐operating characteristic curve for predicting diabetes than fasting glucose, thus HbA 1c discriminated better. The authors propose using HbA 1c ≥ 37 mmol/mol (5.5%) to predict future prediabetes and cystic fibrosis‐related diabetes (CFRD).…”

Diabetes and Prediabetes in Children With Cystic Fibrosis: A Systematic Review of the Literature and Recommendations of the Italian Society for Pediatric Endocrinology and Diabetes (ISPED)

“…According to the ISPAD guidelines ( 5 ), the following two diagnostic categories of CFRD have been established for patients screened with oral glucose tolerance test (OGTT) during periods of stable CF clinical conditions, based on fasting and 2-h glucose values: CFRD without fasting hyperglycemia (CFRD-FH - ) and CFRD with fasting hyperglycemia (CFRD-FH + ) ( Table 11 ). In addition, in symptomatic patients, the CFRD can be diagnosed if random blood glucose level is ≥200 mg/dL (≥11.1 mmol/L) on 2 or more occasions, and if HbA1c is ≥ 48 mmol/mol (6.5%) (48 mmol/mol), even though diagnosis of diabetes can also be made in CF patients that show HbA1c value below this range ( 45 ). During flare-up phases of the disease, when intravenous antibiotic therapy and/or systemic corticosteroid therapy is required, the diagnosis of CFRD can be made if a fasting glycemia ≥126 mg/dL (≥7 mmol/L) or a post-prandial blood glucose ≥200 mg/dL (≥11.1 mmol/L) is present for 48 h.…”

Retinopathy and microalbuminuria are common microvascular complications in cystic fibrosis-related diabetes

“…In their cohort, 36% of patients did not attend for their retinal screening appointment in the year assessed, but of those who did, 42% had evidence of retinopathy, ranging from mild to proliferative, and associated with maculopathy. 17 Choudhury et al 25 performed a retrospective seven-year longitudinal study in this same Welsh cohort and demonstrated that 44% of screened people with CFRD had retinopathy. 25 Yung et al 26 found retinopathy in 16% and 23% of a small cohort of patients at 5 years and 10 years of CFRD respectively, but HbA1c was not significantly different between people with and without retinopathy.…”