Impact of the FIB4 Index on Pre-sarcopenia in Patients with Metabolic-dysfunction Associated Steatotic Liver Disease

Objective To compare the effect of the FIB4 index on skeletal muscle mass (SMM) loss (i.e., pre-sarcopenia) with that of three other liver fibrosis markers [FIB3 index, aminotransferase to platelet ratio index (APRI), and platelet count] or sarcopenia-related factors such as age and body mass index (BMI) in patients with metabolic dysfunction associated with steatotic liver disease (MASLD, 2,093 men and 1,280 women; median age, 55 years). Methods An SMM decrease was defined as a fat-free index, as tested by a bioelectrical impedance analysis, <18 kg/m² in men and <15 kg/m² in women. We compared the diagnostic ability of the above-mentioned six markers to induce an SMM decrease. Results The median BMI was 25.0 kg/m². The median FIB4 index, FIB3 index, APRI, and platelet count were 0.99, -0.40, 2.93 and 25.2 × 10⁴/μL. The prevalence of SMM decrease in men and women was 21.7% (455/2,093) and 16.7% (214/1,280), respectively. For all cases, the percentage of a decreased SMM was 15.0% (372/2,479) in cases with FIB4 index <1.3, 32.1% (268/834) in cases with 1.3< FIB4 index <2.67 and 48.3% (29/60) in cases with FIB4 index >2.67 (overall p<0.0001). In almost all subgroup analyses, the cases were well-stratified according to the FIB4 index. In all cases, the area under the receiver operating characteristic curve (AUC) for SMM decrease was highest for BMI (AUC=0.94), followed by the FIB4 index (AUC=0.67). In all subgroup analyses, except for BMI ≥25 kg/m², the FIB4 index had the second highest AUC for SMM decrease after BMI. Conclusion The FIB4 index may be useful for predicting pre-sarcopenia in patients with MASLD.