Spuriously High Prevalence of Prediabetes Diagnosed by HbA1c in Young Indians Partly Explained by Hematological Factors and Iron Deficiency Anemia
Diabetes Care, 02/20/2012

Hardikar PS et al. – 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.

• The authors 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.
• They also studied the contribution of glycemic and nonglycemic determinants to HbA1c concentrations.

• 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%).