Optimal ALT threshold for the automated diagnosis of MASLD: A population-based study using iLFT

Introduction and objectives: Early diagnosis of metabolic dysfunction-associated steatotic liver disease (MASLD), especially with advanced fibrosis, is crucial due to the increased risk of complications and mortality. Serum alanine aminotransferase (ALT) is commonly used; however, many patients have normal ranges (<55 U/L) who may remain undetected. We investigated the clinical implications of a lower ALT cut-off (>30 U/L) using intelligent liver function testing (iLFT) to identify MASLD patients with and without advanced fibrosis in primary care. Materials and methods: All patients entering the iLFT diagnostic pathway had liver aetiological screening investigations if ALT >30 U/L. In those with MASLD the proportions with and without advanced fibrosis at different ALT thresholds: 31-41 U/L, 42-54 U/L and >= 55 U/L were compared. Results: 16,373 patients underwent iLFT between March 2016 to April 2022. 762 (5 %) patients had MASLD with abnormal fibrosis scores, while 908 (6 %) had MASLD with normal fibrosis scores. 428 (56 %) patients were assessed in liver clinics, where 169 (39 %) had evidence of fibrosis. Of these, 22 (13 %) had ALT 31-41 U/L, 31 (18 %) had ALT 42-54 U/L and 116 (69 %) had ALT >= 55 U/L. 145 (86 %) patients had advanced fibrosis or cirrhosis, where 20 (14 %) had ALT 31-41 U/L, 28 (19 %) had ALT 42-54 U/L and 97 (67 %) had ALT >= 55 U/L. Conclusions: 33 % of MASLD patients with advanced fibrosis or cirrhosis had ALT 31-54 U/L, who would have been missed using the conventional ALT range. This suggests that lowering the ALT cut-off improves diagnosis of MASLD with advanced fibrosis in primary care.