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

Abstract

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 HbA1c 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 HbA1c criteria, 23.3% were prediabetic and 2.6% were diabetic. The negative predictive value of HbA1c 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 B12 deficient (<150 pmol/L), and 22% were folate deficient (<7 nmol/L). On multiple linear regression analysis, HbA1c 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, HbA1c was predicted by higher glycemia (R2 = 25.6%) and lower ferritin (R2 = 4.3%). CONCLUSIONS The use of HbA1c to diagnose prediabetes and diabetes in iron-deficient populations may lead to a spuriously exaggerated prevalence. Further investigation is required before using HbA1c as a screening tool in nutritionally compromised populations.