Given an AST of 50 IU/L and a platelet count of 93,000/µL, what is the aspartate aminotransferase‑to‑platelet ratio index (APRI)?

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APRI Calculation Result

With an AST of 50 IU/L and a platelet count of 93,000/µL, the APRI score is approximately 1.34.

Calculation Method

The APRI is calculated using the formula: APRI = [(AST/ULN AST) × 100] / platelet count (×10⁹/L) 1, 2.

Step-by-Step Calculation:

  • AST value: 50 IU/L
  • Upper limit of normal (ULN) for AST: Typically 40 IU/L (standard reference)
  • Platelet count: 93,000/µL = 93 × 10⁹/L

Formula application:

  • AST/ULN = 50/40 = 1.25
  • (1.25 × 100) / 93 = 125 / 93 = 1.34

Clinical Interpretation

This APRI value of 1.34 falls into an intermediate range that suggests possible significant fibrosis but does not definitively indicate advanced fibrosis or cirrhosis 1, 3.

Fibrosis Risk Stratification:

  • APRI <0.5: Generally excludes significant fibrosis 4, 3
  • APRI 0.5-1.5: Intermediate range; indeterminate for significant fibrosis 1, 3
  • APRI >1.5: Suggests significant fibrosis (Ishak score ≥3) with AUROC of 0.8 1, 2
  • APRI >2.0: Suggests cirrhosis with AUROC of 0.89 1, 2

Context-Specific Thresholds:

Different disease states have varying cutoff values 4:

  • Cystic fibrosis: APRI ≥0.545 suggests advanced CF liver disease
  • Hepatitis C: APRI >1.5 for significant fibrosis, >2.0 for cirrhosis 1, 3
  • General chronic liver disease: Similar thresholds apply 5

Clinical Implications

At APRI 1.34, this patient requires further evaluation with additional noninvasive testing or imaging to clarify fibrosis stage, as this value sits in the indeterminate zone where neither advanced fibrosis can be confirmed nor excluded with confidence 1, 3, 6.

Recommended Next Steps:

  • Consider FIB-4 score for complementary assessment (requires age and ALT) 5
  • Elastography (transient elastography or shear wave elastography) provides superior diagnostic accuracy in this intermediate range 1, 3
  • Clinical context matters: The underlying liver disease etiology (viral hepatitis, MASLD, autoimmune hepatitis, etc.) influences interpretation 1, 5, 7

Important Caveats:

  • APRI can be falsely elevated in acute hepatitis with severe inflammation 1, 2
  • Thrombocytopenia from non-hepatic causes (e.g., hematologic disorders) can artificially elevate APRI
  • The score performs best when AST and platelets are measured during clinical stability, not during acute illness 4
  • APRI has moderate sensitivity (77-82%) but better specificity (78-92%) at higher cutoffs for advanced fibrosis 3, 6

References

1
Guideline

kasl clinical practice guidelines: management of hepatitis c.

Clinical and Molecular Hepatology, 2016

2
Guideline

kasl clinical practice guidelines: management of hepatitis c.

Clinical and Molecular Hepatology, 2014

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