Poor Sensitivity of the Fatty Liver Index Among Lean Individuals

Area of Science:

• Hepatology
• Medical Diagnostics
• Public Health

Background:

• Fatty Liver Index (FLI) is a common tool for detecting steatotic liver disease (SLD).
• Its utility in lean individuals, a specific subgroup, remains unvalidated.
• FLI's reliance on body-size measures raises concerns about its suitability for lean populations.

Purpose of the Study:

• To validate the performance of the Fatty Liver Index (FLI) in detecting steatotic liver disease (SLD) among lean adults.
• To assess the accuracy of FLI thresholds in identifying SLD in lean versus the general population.

Main Methods:

• Utilized National Health and Nutrition Examination Survey (NHANES) 2017-20 data.
• Defined SLD using controlled attenuation parameter (CAP) ≥263 dB/m.
• Assessed FLI diagnostic performance (rule-in ≥60, rule-out <30) overall and in lean individuals identified by ethnicity-adjusted BMI cutoffs.

Main Results:

• The study included 7191 participants; 50% had SLD, including 13.7% of 1739 lean individuals.
• FLI performed poorly in lean participants (sensitivity 6.3% for rule-in), misidentifying individuals.
• Lean individuals flagged by FLI differed significantly from confirmed cases, showing higher BMI and cardiometabolic risk factors.

Conclusions:

• Fatty Liver Index (FLI) is inaccurate for detecting steatotic liver disease (SLD) in lean individuals due to its dependence on body-size measures.
• FLI application to lean populations leads to overestimation of disease severity and misclassification.
• FLI should be avoided in population-based studies focusing on lean individuals with SLD.