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HbA1c promising as predictive measure for cystic fibrosis-related diabetes
Adults with cystic fibrosis and HbA1c levels of 37 mmol/mol or more are at greater risk for dysglycemia and cystic fibrosis-related diabetes than those with lower HbA1c levels, according to findings published in Diabetic Medicine.
“HbA1c assessment can be undertaken on a random basis, and thus can potentially reduce the burden of annual [oral glucose tolerance test], a cumbersome test that requires individuals to travel from long distances in a fasting state, to a [cystic fibrosis] centre,” Maitrayee Choudhury, of the diabetes research group of the division of infection and immunity at the Cardiff University School of Medicine in Cardiff, U.K., and colleagues wrote. “In light of the debate surrounding the OGTT, we explored the possibility of whether HbA1c assessment could be an adjunctive tool in the prediction of individuals who may later develop [cystic fibrosis-related diabetes].”
Choudhury and colleagues conducted a longitudinal study over 7 years with 50 adults with cystic fibrosis (42% women; mean age, 26 years) who visited the All Wales Adult Cystic Fibrosis Centre in Cardiff. Participants were followed between 2006 and 2012 and had fasting plasma glucose and 2-hour postprandial glucose levels measured by OGTT and HbA1c levels measured by high-performance liquid chromatography.
More participants who had mean HbA1c levels of 37 mmol/mol or more developed dysglycemia (n= 18) than those with lower levels (n =14) during follow-up.
The researchers created a receiver-operating characteristic (ROC) curve to measure the association between HbA1c and OGTT with diabetes development. HbA1c had an area under the fitted ROC curve of 0.76 in 2006 (P = .012) and a larger AUC when used as a baseline variable in comparison with FPG, which “suggests that HbA1c level is closely associated with the development of [cystic fibrosis-related diabetes], using OGTT as the outcome diagnostic test,” the researchers said. In addition, abnormal OGTT results were more likely for participants with HbA1c levels of 37 mmol/mol or more than those with lower levels during the 7 years (HR = 3.49; 95% CI, 1.5-8.1).
The researchers also assessed diabetic retinopathy in the study cohort via diabetes retinal screening. Nearly half (n =19) of the participants with cystic fibrosis-related diabetes (n = 43) developed diabetic retinopathy between 2010 and 2012. HbA1c levels were higher for these participants (mean HbA1c, 68 mmol/mol) than those without diabetic retinopathy (mean HbA1c, 54 mmol/mol).
“Although current guidance does not recommend the use of HbA1c as a screening tool in [cystic fibrosis-related diabetes] and the present study also does not advocate this, there is relatively little information concerning the use of HbA1c in prediction of the development of [cystic fibrosis-related diabetes],” the researchers wrote. “However, the present findings suggest that HbA1c could also be used in assessing individuals at risk of developing [cystic fibrosis-related diabetes], in addition to the OGTT, rather than solely in monitoring once a diagnosis has been made.” – by Phil Neuffer
Disclosures: The authors report no relevant financial disclosures.