Glycated Hemoglobin, A Potential Screening Tool for Cystic Fibrosis Related Diabetes

In a study, researchers have reported that glycated haemoglobin (A1C) cutoffs allow early identification of children requiring further CFRD investigations, which may reduce the clinical burden of children with CF. The study findings were published in the Canadian Journal of Diabetes on March 25, 2021.

A recent study carried out by Gilmour et al, suggested a stepwise approach as a first-line screening method for CFRD in adults with CF. It was concluded that only patients with A1C levels between 5.5% and 6.4% should undertake an OGTT annually. However, it has never been tested in patients <18 years of age. Therefore, Dr Geneviève Mailhot and her team conducted a study to document the screening rate for cystic fibrosis-related diabetes (CFRD) in children followed at cystic fibrosis (CF) clinic in Canada. They further evaluated the accuracy of various glycated haemoglobin (A1C) cutoffs to screen for CFRD and impaired glucose tolerance (IGT) in a pediatric CF population.

In this validation study, the researchers calculated the CFRD screening rate over a follow-up period of up to 8 years among children who attended the CF clinic between 1993 and 2018. They compared the test performance of A1C at various thresholds ranging from 5.5% to 6.2% with the oral glucose tolerance test (OGTT) as the reference method. They included children with CF aged ≥10 years with an OGTT performed within 120 days of A1C measurement in the analysis.

Key findings of the study:

• The overall CFRD screening rate was 53.0%.
• Among 256 children, the researchers found that 8.6% had an OGTT-confirmed CFRD diagnosis.
• They noted that the A1C threshold of 5.8% demonstrates an optimal balance between sensitivity (90.9%) and specificity (60.7%) for CFRD screening, leading to a potential reduction of 56.3% of the annual required OGTTs.
• However, they noted that A1C demonstrated poor accuracy for identifying children with IGT.

The authors concluded, "An A1C threshold ≥5.8% allows for identification of children requiring further CFRD investigations, which may reduce the clinical burden of children with CF without compromising the ability of early CFRD diagnosis."

For further information:

DOI: https://doi.org/10.1016/j.jcjd.2021.03.005