Comparative performance of HbA1c 6.5% for FPG >7.0 vs 2hr PG>11.1 criteria for diagnosis of Type 2 diabetes

Background: International expert committee on the use of HbA1c to diagnose diabetes mellitus in 2009 and World Health Organization (WHO) in 2011 has advocated the use of HbA1c to diagnose diabetes mellitus.
Objective: To determine and compare the relationship between the new cut off value of HbA1c with established criteria.
Methods: Thirty-one hypertensive subjects attending Lagos University Teaching Hospital were recruited for HbA1c and standard oral glucose tolerance test. Fasting plasma glucose (FPG) and two-hour plasma glucose (2hrpp) value of e"126mg/ dl and ≤>200mg/dl were used as standard respectively for diagnosis of diabetes. The HbA1c of e"6.5% was used to diagnose diabetes. The performance and correlation of HbA1c with FPG and 2hrpp were calculated and results were compared.
Results: Mean age of the subjects was 53.97±6.27years. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), efficiency and correlation of FPG is 50%, 68%, 27%, 85%, 64% and 0.5 respectively while the sensitivity, specificity, PPV, NPV, efficiency and correlation of 2hrpp is 73.91%, 62.5%,85%, 41.66%, 70.97% and 0.73% respectively. There was a significant difference between FPG and 2hrpp interms of sensitivity, PPV and NPV.
Conclusion: The results of HbA1c with 2hrpp has better correlation, sensitivity, and PPV compared to HbA1c with FPG. Key words: HbA1c, Diabetes diagnosis, Fasting Plasma Glucoe, 2-hour post-prandial glucose.