Lok Index Calculator
Estimates the probability of cirrhosis using platelet count, AST, ALT, and INR.
Patient laboratory values
Enter current laboratory results using the units shown.
Result
Calculated from the laboratory values above.
Enter all values and select Calculate Lok Index.
Calculation and clinical note
Lok Index = 1 / (1 + e−LP), where LP = −5.56 − (0.0089 × platelets) + (1.26 × AST/ALT) + (5.27 × INR).
This tool supports clinical assessment and should not be used as a standalone diagnosis. Interpret results alongside the patient’s clinical history, examination, and appropriate confirmatory testing.
Reference: Lok AS, et al. Hepatology. 2005;42:282–292.
The Lok index (also called Lok score / Lok model) is a non-invasive blood-test–based prediction model that estimates the probability (0 to 1) that a patient has liver cirrhosis, originally developed/validated in chronic viral hepatitis populations.
It uses 4 routine labs:
- Platelet count
- AST
- ALT (to form the AST/ALT ratio)
- INR (or prothrombin time–based coagulation measure)
How it’s calculated (common implementation)
It’s a logistic regression model:
- LP (log-odds) =
-5.56 − 0.0089*(platelets) + 1.26*(AST/ALT) + 5.27*(INR) - Lok index =
exp(LP) / (1 + exp(LP))
(Platelets are typically entered as ×10⁹/L, numerically the same as K/µL.)
How people often interpret it (rule-of-thumb cutoffs)
Cutoffs vary by pathway/study, but commonly:
- Lok < 0.20 → lower probability of cirrhosis (“rule-out leaning”)
- Lok > 0.50 → higher probability of cirrhosis (“rule-in leaning”)
- 0.20–0.50 → indeterminate
Important limitations
It’s a screening/decision-support tool, not a diagnosis by itself. Results can be affected by things that change platelets, AST/ALT, or INR for reasons other than cirrhosis (e.g., acute hepatitis, alcohol use, anticoagulants/vitamin K issues, lab variability). Reviews of noninvasive fibrosis testing emphasize using these scores alongside clinical context and/or elastography when needed.
