Predictors of advanced liver fibrosis and the performance of fibrosis scores: lean compared to non-lean metabolic dysfunction-associated steatotic liver disease (MASLD) patients.

Background: Non-alcoholic fatty liver disease (NAFLD) in lean patients differs from that of NAFLD in non-lean patients. However, current data regarding predictors of advanced fibrosis and the performance of fibrosis-4 index (FIB-4) and NAFLD fibrosis score (NFS) in lean compared to non-lean metabolic dysfunction-associated steatotic liver disease (MASLD) patients is insufficient.
Methods: This was a cross-sectional study. Lean was defined as Body Mass Index <25 kg/m ² . Advanced fibrosis (F3-F4) was detected by liver biopsy or two-dimension shear wave elastography (2D-SWE). Predictors of advanced fibrosis were identified using logistic regression and area under ROC curves (AUROC) were derived for FIB-4 and NFS.
Results: Lean patients (N.=153) comprised 19.2% of the MASLD cohort. Advanced fibrosis was associated with the number of cardiometabolic risk factors (CMRF) in lean (OR=2.06, P=0.011) and non-lean (OR=1.58, P<0.001) patients, however, hypertension and diabetes or impaired fasting glucose were significant only among non-lean. Age was associated with advanced fibrosis in both subgroups with age ≥65 showing higher odds in lean compared to non-lean patients (P=0.016). Non-lean patients had higher odds for advanced fibrosis relative to lean patients (OR=4.8, P=0.048). FIB-4 and NFS predicted advanced fibrosis among lean (AUROC=0.79 and AUROC=0.85, respectively) and non-lean (AUROC=0.79 and AUROC=0.76, respectively) patients. NFS ≥-1.445 showed higher specificity among lean compared to non-lean (P<0.001) and compared to that of FIB-4 ≥1.3 in lean patients (P<0.001).
Conclusions: The number of CMRF was predictive of advanced fibrosis in both subgroups while age ≥65 showed higher odds among lean patients. NFS ≥-1.445 is more specific than FIB-4 ≥1.3 for advanced fibrosis prediction in lean patients. These findings may help identify high-risk lean MASLD patients for further liver fibrosis stage assessment.