Spuriously High Prevalence of Prediabetes Diagnosed by HbA1c in Young Indians Partly Explained by Hematological Factors and Iron Deficiency Anemia.

OBJECTIVE--To examine the influence of glycemic and nonglycemic parameters on HbA1c concentrations in young adults, the majority of whom had normal glucose tolerance. RESEARCH DESIGN AND METHODS--We compared the diagnosis of normal glucose tolerance, prediabetes, and diabetes between a standard oral glucose tolerance test (OGTT; World Health Organization 2006 criteria) and HbA_1c concentrations (American Diabetes Association [ADA] 2009 criteria) in 116 young adults (average age 21.6 years) from the Pune Children's Study. We also studied the contribution of glycemic and nonglycemic determinants to HbA1c concentrations. RESULTS--The OGTT showed that 7.8% of participants were prediabetic and 2.6% were diabetic. By ADA HbA_1c criteria, 23.3% were prediabetic and 2.6% were diabetic. The negative predictive value of HbA_1c was 93% and the positive predictive value was 20% (only 20% had prediabetes or diabetes according to the OGTT; this figure was 7% in anemic participants). Of participants, 34%were anemic, 37%were iron deficient (ferritin<15 ng/mL), 40% were vitamin B₁₂deficient (<150 pmol/L), and 22% were folate deficient (<7 nmol/L). On multiple linear regression analysis, HbA^1c was predicted by higher 2-h glucose (R² = 25.6%) and lower hemoglobin (R²= 7.7%). When hematological parameters were replaced by ferritin, vitamin B₁₂, and folate, HbA_1c was predicted by higher glycemia (R² = 25.6%) and lower ferritin (R² = 4.3%). CONCLUSIONS--The use of HbA_1c to diagnose prediabetes and diabetes in iron-deficient populations may lead to a spuriously exaggerated prevalence. Further investigation is required before using HbA_1c as a screening tool in nutritionally compromised populations. [ABSTRACT FROM AUTHOR]