FIB-4 Reliability in Patients With Severe Obesity: Lower Cutoffs Needed?

Liver biopsy is the gold standard to evaluate hepatic fibrosis; however, it has many drawbacks, especially in patients with severe obesity. Noninvasive testing such as the FIB-4 score is increasingly being used as the initial screening tool to identify patients at risk for advanced fibrosis. The broader applicability of FIB-4 and the precision of its cutoff values remain uncertain in metabolic dysfunction-associated steatotic liver disease and patients with severe obesity. Our study explored the correlation between FIB-4 scores and intraoperative liver biopsy in patients with severe obesity undergoing bariatric surgery.

A total of 632 patients with severe obesity underwent preoperative vibration-controlled transient elastography and intraoperative liver biopsy during bariatric surgery from January 2020 to August 2021. Variables collected included patient demographics, laboratory values, abdominal ultrasound, vibration-controlled transient elastography, and liver biopsy results. ANOVA 1-way test, χ 2 tests, and Fisher exact tests were used for quantitative and qualitative variables, respectively. The 95% CIs for the mean FIB-4 scores were used to generate surrogate cutoff values. The proposed FIB-4 cutoffs for F0-1, F2, F3, and F4 were 0.62 (CI: 0.59, 0.64), 0.88 (0.74, 1.01), 1.24 (0.94, 1.54), and 1.53 (0.82, 2.24), respectively. Area under the curve (AUC) methods were used to compare traditional to proposed cutoff values.

Applying the traditional FIB-4 cutoffs to approximate advanced fibrosis yielded an AUC of 0.5748. Use of the proposed FIB-4 cutoffs increased the AUC to 0.6899. The proposed FIB-4 cutoffs correctly identified 40 patients with biopsy-proven advanced fibrosis (F3-F4), all of which would have been missed using traditional cutoffs.

Our study revealed that the use of the currently accepted FIB-4 cutoffs as the screening modality for identifying patients with advanced fibrosis due to metabolic dysfunction-associated steatotic liver disease is insufficient and will result in missing patients with histologically confirmed advanced fibrosis. Use of the revised FIB-4 scores should be considered to diagnose patients with severe obesity at high risk of liver disease progression.