Discordance between adiposity and FIB-4 risk classification in US adults

Purpose The fibrosis-4 index (FIB-4) is a widely used noninvasive tool for fibrosis risk stratification, however, the relationship between adiposity and FIB-4-based risk classification remains unclear. We evaluated the associations between multiple measurements of adiposity and FIB-4 risk classification in a nationally representative sample of U.S. adults. Methods We analyzed data from 10,711 adults aged 35–65 years from the 2011–2018 NHANES. Examined anthropometric measures included body mass index (BMI), total body fat percentage (TBFP), waist circumference (WC), and waist-to-hip ratio (WH). We conducted logistic regression models to evaluate the association between anthropometric measurements and high-risk FIB-4 classification and to assess whether these associations differed by age group. Results Most participants had low-risk FIB-4 scores (72.9%), followed by intermediate-risk (25.1%) and high-risk (2%). Individuals with low FIB-4 risk classification had higher BMI, TBFP and WC ( p < 0.01). In interaction models, the inverse associations between adiposity measures and high-risk FIB-4 classifications varied by age group. Among adults aged 51–65 years, higher BMI and TBFP were associated with lower odds of high-risk FIB-4 classification, whereas these associations were not significant for adults aged 35–50 years. Conclusion Higher adiposity was associated with lower likelihood of high-risk FIB-4 classification. Age-stratified analyses suggested a potential discordance in the association between adiposity and FIB-4 risk classification across age groups. These findings suggest a potential discordance between adiposity-related metabolic risk and FIB-4-based risk classification, suggesting the need for age- and adiposity-informed risk assessment strategies for individuals at risk for hepatic fibrosis.