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

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."

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