Normal Limit for Serum Alanine Aminotransferase Level and Distribution of Metabolic Factors in Old Population of Kalaleh, Iran

BACKGROUNDS Normal or elevated values of serum alanine aminotransferase level (ALT) vary in different studies mostly related to characteristics of reference population including age, gender, body mass index, nonalcoholic fatty liver disease (NAFLD), and metabolic syndrome prevalence. OBJECTIVES To measure upper normal limit (UNL) for serum ALT in an apparently healthy Iranian old population (which we had not sufficient data before this study), and its modulating factors. PATIENTS AND METHODS All inhabitants (> 50 years old) of Kalaleh, Golestan, Iran (N = 1986) were invited to the study. ALT measurements were performed for all subjects using the same laboratory method. Upper limit of normal (ULN) ALT was calculated based on its 95th percentile in normal weight subjects. Modulating factors of ALT were determined by multivariate analysis. RESULTS A total of 1309 subjects, with the mean age of 61.5 ± 7.5 years were included. UNL of ALT was 18.8 U/L and 21.4 U/L in women and men, respectively. Based on univariate analysis, waist circumference (r = 0.124, P = 0.01), body mass index (r = 0.118, P = 0.01), triglyceride (r = 0.143, P = 0.01), and having metabolic syndrome (OR = 2.04) modulate ALT levels in men. Also triglyceride (r = 0.119, P = 0.01) modulates ALT levels in women. CONCLUSIONS The calculated level for UNL of ALT is considerably far lower than previous accepted value. Age, gender, ethnicity, and metabolic factors should be accounted in future studies to determine normal ALT level.