Bedogni 2006: Original Fatty Liver Index Validation

Background

The Fatty Liver Index (FLI) was developed by Dr. Giorgio Bedogni and colleagues at the Italian Liver Research Unit as a simple, non-invasive algorithm to predict hepatic steatosis. Published in BMC Gastroenterology in 2006, this study established FLI as the first widely validated fatty liver screening tool using routine clinical parameters.

Study Design and Population

Derivation Cohort:

• •216 patients with suspected liver disease from Campogalliano, Italy
• •Hepatic steatosis confirmed by ultrasonography (reference standard)
• •Age range: 18-75 years
• •Prevalence of hepatic steatosis: 61%

Validation Cohort:

• •496 subjects from the general population (Dionysos Nutrition and Liver Study)
• •Same ultrasound criteria for steatosis diagnosis
• •Lower steatosis prevalence: 34%

Formula Development

The researchers used logistic regression to identify the strongest independent predictors of hepatic steatosis:

FLI Formula:

FLI = (e^L / (1 + e^L)) × 100

Where L = 0.953 × ln(TG) + 0.139 × BMI + 0.718 × ln(GGT) + 0.053 × waist − 15.745

Components:

1. •Triglycerides (mg/dL): Reflects hepatic lipid export and insulin resistance
2. •BMI (kg/m²): Surrogate for overall adiposity
3. •GGT (U/L): Marker of hepatic oxidative stress and steatosis
4. •Waist circumference (cm): Reflects visceral adiposity

Diagnostic Performance

Derivation Cohort:

• •AUROC: 0.84 (95% CI: 0.81-0.87)
• •FLI <30: Rules OUT steatosis (sensitivity 87%)
• •FLI ≥60: Rules IN steatosis (specificity 86%)

Validation Cohort:

• •AUROC: 0.83 (95% CI: 0.79-0.86)
• •Similar cutoff performance maintained

Interpretation Framework:

FLI Score	Interpretation	Clinical Action
<30	Low probability	Fatty liver unlikely
30-59	Intermediate	Further evaluation may be needed
≥60	High probability	Likely fatty liver, consider imaging

Methodological Strengths

1. •Population-based validation: Both clinical and community samples
2. •Practical components: All from routine clinical assessments
3. •Clear cutoffs: Actionable thresholds for clinical decision-making
4. •Transparent formula: Fully disclosed, allowing independent validation

Limitations Acknowledged

• •Ultrasound reference: Less sensitive than MRI for mild steatosis
• •Italian population: May require calibration for other ethnicities
• •Steatosis only: Does not assess inflammation or fibrosis
• •GGT variability: Can be elevated from non-hepatic causes

Subsequent Validation

Since publication, FLI has been validated in numerous populations:

• •Finnish, German, Dutch, Korean, Chinese cohorts
• •Consistent AUROC 0.80-0.85 across studies
• •Correlation with liver biopsy-proven steatosis
• •Association with metabolic outcomes beyond liver disease

Metabolic Health Perspective

The FLI components beautifully capture metabolic dysfunction:

1. •Triglycerides: Direct marker of hepatic lipogenesis and insulin resistance
2. •GGT: Reflects oxidative stress from fatty liver metabolism
3. •BMI and waist: Capture the adiposity driving hepatic fat accumulation

For metabolic health optimization, FLI serves as:

• •Screening tool: Identifies those likely to have fatty liver
• •Progress marker: Tracks response to lifestyle intervention
• •Risk stratification: Higher FLI predicts cardiovascular events and diabetes
• •Motivation tool: Tangible number for patient engagement

The simplicity of FLI — requiring only a tape measure, scale, and basic blood tests — makes it ideal for primary care screening and longitudinal monitoring of metabolic health interventions.