The optimal cut-points of alanine aminotransferase for screening metabolic syndrome in Iranian adults

Abstract

Abstract Background Studies reported that the activity of the alanine aminotransferase (ALT) enzyme becomes the main biomarker for screening liver cell damage such as non-alcoholic fatty liver disease (NAFLD). Since individuals with metabolic syndrome (Mets) are at high risk for NAFLD, we aimed to determine the gender-specific ALT thresholds for screening Mets in the Tehranian population. Methods We did a cross-sectional study (2018–2022) of 4968 adults aged 20–70 years (2732 female). Multivariable logistic regression analysis was done to assess the association between ALT level and the prevalence of Mets and each component. Moreover, the gender-specific ALT cut-off point was determined using the maximum Youden's index. The area under the receiver operating characteristics curves (AUC) was calculated to derived thresholds and compared to the previously introduced cut-off points from the American College of Gastroenterology (ACG; ALT > 19 U/L for females, > 29 U/L for males). We also examined the diagnostic performance of the derived cut-off points in the 11,147 individuals (7,154, women) from Atherosclerosis Risk in Communities (ARIC) study. Results The odds ratio (OR) of the logistic regression shows that each 5-U/L increase in ALT level was associated with prevalent Mets [19% for females and 8% for males] and its components (ranging from 7–19% in females and 3–10% in males; all p-value < 0.05). The suggested cut-off point for ALT among men was 21 U/L with a sensitivity of 72.1% and specificity of 47.1%; considering the threshold of 18 U/L the corresponding values were 57.9% and 66.5%, respectively. Compared to the ACG guideline, the AUC of our suggested threshold increased in males (60% vs. 56%, respectively) while for females it remained the same as in the pretest (≈ 62%). Using ARIC data, our suggested threshold showed almost the same AUC values compared to the ACG threshold among females (58% vs. 57%, respectively), while among males, the highest AUC was observed for our suggested cut-off points (56%), followed by ACG thresholds (53%). Conclusion The cut-off point for screening Mets among Iranian women was almost the same with the lower suggested threshold of American guidelines but remarkably lower for defined abnormal ALT levels in males.