Lok Index (Cirrhosis Probability) Calculator
Inputs: Platelets, AST, ALT, INR. Output: Lok index (0–1) and %.
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.
