Nonalcoholic Fatty Liver Disease and Liver Fibrosis in Bariatric Patients: Tehran Obesity Treatment Study (TOTS)

Non-alcoholic fatty liver disease (NAFLD) has become a leading cause of chronic liver disease worldwide. We aimed to study this condition and liver fibrosis in bariatric patients at baseline using ultrasound, NAFLD fibrosis score (NFS), and fibrosis index-4 (FIB-4).
Adult patients with morbid obesity without other possible causes of liver pathology were evaluated. Liver biopsy was performed in a subset of patients. Diagnostic accuracy of tests was assessed using area under the receiver operating-characteristic curve (AUROC).
Overall, 1944 patients with mean age of 38.3 ± 10.8 years and body mass index of 44.6 ± 6.4 kg/m2 comprised the study population. Liver Biopsy showed features of NAFLD in 70%; 60.3% had nonalcoholic fatty liver and 9.6% steatohepatitis. Older age and higher transaminase levels were associated with higher NAFLD activity score. Fibrosis was present in 23.3% with the majority having F1. Ultrasound detected steatosis in 76.8%, with two-thirds having grade I to II fatty liver. Metabolic syndrome, hemoglobin A1c, age, and alanine transaminase were the strongest risk factors for fatty liver. Ultrasound showed an AUROC of 0.75 (95% confidence interval 0.63-0.86) for NAFLD with a sensitivity and specificity of 72.5% and 68.2%, respectively (cutoff of grade II). For diagnosis of fibrosis, FIB-4 had an AUROC of 0.72 (0.58-0.86) with 93.3% sensitivity and 43.1% specificity (cutoff of 0.50). NFS failed to show a significant AUROC curve for diagnosing fibrosis.
Our findings confirmed a high prevalence of NAFLD in morbidly obese patients. Despite this high prevalence, fibrosis was uncommon and low-grade. This study questions the use of current cutoffs for NFS and FIB-4 in all patients.