Reassessment of the Diagnostic Accuracy of HbA1c and Glucose for Type 2 Diabetes: A Systematic Review and Meta-Analysis of Observational Studies
Abstract
Aims: This systematic review and meta-analysis evaluated the diagnostic performance of HbA1c, fasting plasma glucose (FPG), and 1-h plasma glucose (1hPG) against the 2-h plasma glucose standard (≥ 11.1 mmol/L) in adults without previously diagnosed diabetes.
Methods: A comprehensive search of Medline and CENTRAL (until 09.2025) identified population-based studies considering all available cutoff values for these markers. Diagnostic accuracy was estimated using bivariate random-effects models. Summary ROC curves and optimal cutoff values were derived using a Weibull accelerated failure time approach and the Youden index. Subgroup analyses explored potential differences across continents. The certainty of evidence (CoE) was evaluated using the GRADE approach.
Results: Fifty-eight studies including 276,203 participants were synthesised. Overall, FPG showed higher diagnostic accuracy than HbA1c, with an optimal cutoff of 6.3 mmol/L [95% confidence interval 6.0 mmol/L; 6.5 mmol/L], yielding 73% [68%; 78%] sensitivity and 91% [89%; 94%] specificity. The optimal HbA1c cutoff was 47 [42; 49] mmol/mol (i.e., 6.5% [6.0%; 6.6%]), with 62% [51%; 80%] sensitivity and 92% [77%; 96%] specificity. The CoE was low. Across all regions, FPG consistently outperformed HbA1c. Optimal FPG cutoff values ranged from 5.3 mmol/L in North America to 6.5 mmol/L in Asian countries, and from 41 mmol/mol (5.9%) in Asian countries to 45 mmol/mol (6.3%) in North America for HbA1c.
Conclusions: These results…
How strong is the evidence?
Evidence Hub reads this as a meta-analysis, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid. Reported size: 276,203 participants or records.
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