The relationship between HbA1c and fasting plasma glucose in patients with increased plasma liver enzyme measurements

Abstract

HbA(1c) is currently being introduced for diagnostic purpose in diabetes. Previous studies have, however, indicated that patients with liver disease have false low HbA(1c) levels. We therefore investigated the correlation between HbA(1c) and plasma glucose in patients with different levels of increased liver enzyme concentrations. Data from 10,065 patients with simultaneous measurement of HbA(1c), venous fasting plasma glucose, alanine aminotransferase and γ-glutamyl transferase were extracted from our laboratory database. Correlations were investigated in four patient groups divided according to their liver enzyme concentrations. The correlation between HbA(1c) and plasma glucose was high in all groups, with r = 0.77 for men and r = 0.78 for women (P < 0.001), a correlation confirmed with multiple regression analysis (P < 0.001). However, interaction analysis revealed that linear regression lines were significantly different for men and women, with increase of both liver enzyme measurements and also, for women, with increased alanine aminotransferase. When compared with biological variation for HbA(1c), only men with increased measurements of both liver enzymes had a clinically important decrease in HbA(1c). Increased liver enzyme concentrations do not bias the correlation between HbA(1c) and fasting plasma glucose. However, men with low plasma glucose and increased concentrations of both liver enzymes do have a slightly decreased HbA(1c) and, if the clinical suspicion is strong enough, one should consider supplement testing.