Laboratory Evaluation and Risk Stratification for Hepatic Steatosis

Initial Laboratory Evaluation

• All patients with suspected hepatic steatosis should undergo a comprehensive metabolic panel—including AST, ALT, alkaline phosphatase, GGT, total and conjugated bilirubin, CBC with platelets, fasting glucose or HbA1c, lipid panel, and viral hepatitis serologies—followed immediately by calculation of a fibrosis risk score (FIB‑4 or NAFLD Fibrosis Score) to identify those at risk for advanced fibrosis. 1

• AST and ALT are required to assess hepatocellular injury and to compute fibrosis scores; age‑ and sex‑specific healthy normal ranges should be used rather than generic laboratory reference intervals. 4

• An AST/ALT ratio > 1 suggests more advanced disease or an alcoholic etiology. 5

• Alkaline phosphatase and GGT are measured to evaluate cholestatic injury; GGT is also a key component of the Fatty Liver Index. 4 6

• Total and conjugated bilirubin assess hepatic synthetic function; an elevated conjugated fraction may indicate advanced disease or biliary obstruction. 4

• Platelet count is essential for fibrosis scoring (FIB‑4, APRI) and thrombocytopenia can signal portal hypertension or advanced fibrosis. 2

• Fasting glucose or HbA1c should be obtained to identify diabetes, a major risk factor for NAFLD progression. 1

• Fasting insulin is required when calculating the NAFLD Liver Fat Score. 7

• A lipid panel (triglycerides, cholesterol) is needed for metabolic‑syndrome assessment and for the Fatty Liver Index. 6

• Viral hepatitis serologies (HBsAg, anti‑HCV) must be performed to exclude chronic viral hepatitis as an alternative cause of liver injury. 3

• Alcohol consumption should be screened with validated tools (AUDIT or AUDIT‑C); thresholds of < 14 drinks/week for women and < 21 drinks/week for men are used to differentiate NAFLD from alcohol‑related disease. 2

• Autoimmune markers (ANA, anti‑smooth muscle antibody) are indicated when clinical features suggest an autoimmune liver disorder. 3

Fibrosis Risk Stratification

• Every patient with hepatic steatosis requires immediate calculation of either the FIB‑4 or the NAFLD Fibrosis Score, regardless of presumed etiology. 2

• FIB‑4 formula: Age × AST ÷ (Platelet × √ALT). 2

• FIB‑4 cut‑offs:
   < 1.3 (or < 2.0 if age > 65) → low risk; repeat testing in 2–3 years.
   1.3–2.67 → intermediate risk; proceed to elastography.
  * > 2.67 → high risk for advanced fibrosis; refer to hepatology. 2

• NAFLD Fibrosis Score incorporates age, BMI, presence of diabetes, AST/ALT ratio, platelet count, and albumin. 1 2

• NAFLD Fibrosis Score cut‑offs:
   < ‑1.455 → low risk.
   ‑1.455 to 0.676 → indeterminate.
  * > 0.676 → high risk for advanced fibrosis. 1 2

Non‑Invasive Steatosis Scoring Systems (when imaging unavailable)

Timing, Follow‑Up, and Monitoring

• Laboratory testing should be performed when the patient is clinically stable; acute illness or recent antibiotic use can confound results. 4

• Annual screening for hepatic steatosis and fibrosis is recommended for all at‑risk individuals from the time of diagnosis. 4

• Persistent laboratory abnormalities lasting > 3–6 months warrant further diagnostic evaluation, even if initially mild. 4

• In patients classified as low‑risk by FIB‑4, repeat calculation every 2–3 years is advised to detect disease progression. 2

Common Pitfalls to Avoid

• Do not rely on generic laboratory reference ranges for ALT; use sex‑specific healthy normals.

• Do not omit fibrosis risk stratification simply because steatosis appears mild on imaging. 3

• Recognize that 60–80 % of individuals with steatosis are asymptomatic and may have normal or only minimally elevated aminotransferases. 9

• Normal platelet counts do not exclude cirrhosis; metabolic‑syndrome‑related thrombocytosis can mask relative thrombocytopenia. 4

• Do not delay evaluation awaiting enzyme elevations of 1.5–2 × the upper limit of normal, as this postpones diagnosis. 4