HOMA-IR and HOMA2-IR estimation based on glycated hemoglobin as an alternative for fasting glucose.

Background: Diabetes mellitus is a major global public health problem. Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) is a key laboratory index in the assessment of insulin resistance. The calculation of HOMA-IR and its updated version HOMA2-IR are partly based on plasma glucose determinations, which are prone to important pre-analytical errors. As glycated hemoglobin (Hb) fractions strongly correlate with fasting glucose levels and are more stable analytes, we explored the possibilities of using glycated Hb fractions for calculating HOMA-IR.

Methods: Labile Hb and HbA_1c fractions were simultaneously assayed on a Tosoh G8 analyzer and expressed as %. Fasting glucose was measured in fluoride plasma using a hexokinase method. A Lumipulse G1200 luminescence immunoassay was used to measure serum insulin. The HOMA-IR and HOMA2-IR values were compared to corresponding indices calculated using glucose and glycated Hb fractions.

Results: Labile Hb could be measured with between-run CVs of 2.2-2.3%. Labile Hb correlated with both glycemia (r = 0.80) and HbA_1c results (r = 0.73). HbA1c-derived estimated average glucose (eAG)-based HOMA calculation correlated very well with HOMA-IR (r² = 0.9972). Based on eAG calculations, HOMA2-IR (%B, %S, and IR) gave comparable results, as compared to labile Hb-based calculations, in particular for fasting plasma glucose values between 4.44 and 6.67 mmol/L.

Conclusions: HbA1c and eAG are practical alternatives for glucose for estimating HOMA-IR. The use of glycated Hb enables home sampling for HOMA-IR and HOMA2-IR calculation.