Agreement Between HbA1c and Continuous Glucose Monitoring–Derived Glycemic Metrics in Adults with Cystic Fibrosis Related Diabetes

Ammar Ahmed; Jaspreet Batth; Qi Wang; Timothy B. Vigers; Katie Larson Ode; Christine L. Chan; Amir A. Moheet

doi:10.1016/j.eprac.2026.04.007

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Agreement Between HbA1c and Continuous Glucose Monitoring–Derived Glycemic Metrics in Adults with Cystic Fibrosis Related Diabetes

Journal article

Peer reviewed

Agreement Between HbA1c and Continuous Glucose Monitoring–Derived Glycemic Metrics in Adults with Cystic Fibrosis Related Diabetes

Ammar Ahmed, Jaspreet Batth, Qi Wang, Timothy B. Vigers, Katie Larson Ode, Christine L. Chan and Amir A. Moheet

Endocrine practice

04/20/2026

DOI: 10.1016/j.eprac.2026.04.007

PMID: 42019904

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Abstract

Cystic fibrosis related diabetes (CFRD) is a prevalent complication of cystic fibrosis that requires accurate assessment of glycemic control to guide management. Whether HbA1c reliably reflects mean glycemia in adults with CFRD, particularly in the context of CGM adoption and modern CFTR modulator therapy, remains uncertain. This retrospective cross-sectional study, conducted at a single CF center, evaluated adults with confirmed CFRD who had a laboratory HbA1c paired with at least 30 days of CGM data with ≥70% active sensor time during the preceding 30–90 days. Individuals with conditions that affect HbA1c reliability, such as anemia, advanced chronic kidney disease, or pregnancy, were excluded. Forty-nine adults met the inclusion criteria (mean age 43.9 ± 11.6 years; 69.4% male), with high CGM adherence (median sensor active time of 97%). Their mean HbA1c was 7.3% ± 1.1% (56 ± 12 mmol/mol), while mean GMI and mean sensor glucose were 7.6% ± 1.0% (60 ± 11 mmol/mol) and 178.6 ± 40.3 mg/dL (9.9 ± 2.2 mmol/L), respectively. HbA1c demonstrated strong correlations with GMI (r = 0.90; P < .0001) and mean sensor glucose (r = 0.90; P < .0001). Bland–Altman analysis showed a mean bias of +0.30% (GMI–HbA1c), with 95% limits of agreement from –0.65% to +1.25% and no proportional bias across the glycemic range. These findings indicate that HbA1c closely reflects CGM-derived mean glycemia in adults with established CFRD. While CGM metrics provide complementary clinical information, integrating both measures may improve monitoring and therapeutic decision-making in CFRD care. •In adults with cystic fibrosis–related diabetes receiving CFTR modulator therapy, HbA1c shows a strong correlation with CGM-derived mean glucose.•High CGM adherence in this cohort allows a reliable evaluation of the concordance between HbA1c and CGM metrics.•Minimal systematic bias was observed between HbA1c and GMI, indicating acceptable agreement in modern CFRD care.•These findings challenge earlier assumptions that HbA1c systematically underestimates glycemia in cystic fibrosis.•The results support the use of HbA1c as a practical and accessible marker for glycemic assessment in CFRD when CGM data are unavailable.

CFTR modulator therapy

Continuous glucose monitoring

Cystic fibrosis related diabetes

Glucose Management Indicator

glycemic monitoring in CFRD

Hemoglobin A1c

Details

Title: Subtitle: Agreement Between HbA1c and Continuous Glucose Monitoring–Derived Glycemic Metrics in Adults with Cystic Fibrosis Related Diabetes
Creators: Ammar Ahmed - University of Minnesota Medical Center
Jaspreet Batth - University of Minnesota Medical Center
Qi Wang - University of Minnesota
Timothy B. Vigers - University of Colorado Anschutz Medical Campus
Katie Larson Ode - University of Iowa
Christine L. Chan - Children's Hospital Colorado
Amir A. Moheet - University of Minnesota Medical Center
Resource Type: Journal article
Publication Details: Endocrine practice
DOI: 10.1016/j.eprac.2026.04.007
PMID: 42019904
ISSN: 1530-891X
Publisher: Elsevier Inc
Language: English
Electronic publication date: 04/20/2026
Academic Unit: Endocrinology and Diabetes; Stead Family Department of Pediatrics
Record Identifier: 9985157524302771

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