# FIB-4 Fibrosis Index Calculator > FIB-4 Fibrosis Index Calculator is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15). Computes the FIB-4 liver fibrosis index from age, AST, ALT, and platelet count for MASH/NASH prior-authorization workflows ## Facts - Endpoint: GET https://api.magentlab.com/api/calc/fib4 - Price: $0.005/call - Payment: x402 - Status: unknown - Last checked: 2026-09-15 - Activations on Zero: 0 - Tags: x402 - Canonical page: https://www.zero.xyz/c/fib-4-fibrosis-index-calculator-753fb585 - Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_E1OVNQYpeFQMYfS69KfWM Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently. ## How to call it through Zero Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`): ```sh zero fetch --capability fib-4-fibrosis-index-calculator-753fb585 ``` Example prompt: Calculate the FIB-4 fibrosis index for a 54-year-old patient with an AST of 72 U/L, ALT of 58 U/L, and a platelet count of 145 × 10⁹/L so I can include it in a MASH prior-auth submission. ## When to prefer this Use this endpoint when you need a deterministic, citable FIB-4 score for MASH/NASH prior-authorization paperwork or clinical decision support and want a zero-configuration arithmetic API rather than a full EHR integration or ML-based fibrosis model. Ideal when you already have the four required lab values (age, AST, ALT, platelets) and need a reproducible, auditable result with a published reference. Prefer this over manual spreadsheet calculation when building automated prior-auth workflows or population health pipelines that require consistent fibrosis staging. ## Known failure modes - Missing required query parameters (age, ast_u_l, alt_u_l, platelets_10e9_l) returns a 400 validation error - Out-of-range values (e.g., age < 18 or > 120, platelets < 1 or > 2000, AST/ALT < 1 or > 10000) return validation errors - Division-by-zero edge case if platelets or ALT is zero (guarded by minimum value constraints) - Payment failure via x402 protocol returns 402 Payment Required before computation - Network timeout if the API is unreachable ## How this service works FIB-4 fibrosis index from age, AST, ALT, and platelets. Use for MASH/NASH prior-auth arithmetic. Deterministic published index with citation; not a diagnosis. ## Output Returns the computed FIB-4 index value (a continuous numeric score) derived from the published Sterling et al. formula: (age × AST) / (platelets × √ALT). The response includes the numeric score, interpretive thresholds (e.g., <1.30 = low risk, >2.67 = high risk), and a citation to the originating publication. No diagnosis is made; the result is deterministic arithmetic based on the four input lab values. ## Request schema (JSON Schema) ```json { "type": "object", "$schema": "https://json-schema.org/draft/2020-12/schema", "required": [ "input" ], "properties": { "input": { "type": "object", "required": [ "type", "method" ], "properties": { "type": { "type": "string", "const": "http" }, "method": { "enum": [ "GET", "HEAD", "DELETE" ], "type": "string" }, "headers": { "type": "object", "additionalProperties": { "type": "string" } }, "queryParams": { "type": "object", "required": [ "age", "ast_u_l", "alt_u_l", "platelets_10e9_l" ], "properties": { "age": { "type": "integer", "description": "Age in years (18-120)." }, "alt_u_l": { "type": "number", "description": "Alanine aminotransferase in U/L (1-10000)." }, "ast_u_l": { "type": "number", "description": "Aspartate aminotransferase in U/L (1-10000)." }, "platelets_10e9_l": { "type": "number", "description": "Platelet count in 10^9/L (1-2000)." } } } }, "additionalProperties": false }, "output": { "type": "object", "required": [ "type" ], "properties": { "type": { "type": "string" }, "example": { "type": "object" } } } } } ``` ## Response schema (JSON Schema) ```json { "type": "json", "example": { "path": "/api/calc/fib4", "count": 2, "items": [ { "fib4": 3.95, "alt_u_l": 40, "ast_u_l": 100, "formula": "fib4", "citation": { "id": "sterling-2006", "doi": "10.1002/hep.21172", "title": "Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection", "source": "Hepatology. 2006;43(6):1317-1325", "authors": "Sterling RK, Lissen E, Clumeck N, et al." }, "age_years": 50, "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "sterling_band": "high", "platelets_10e9_l": 200, "formula_expression": "FIB-4 = (age_years * AST_U_L) / (platelets_10e9_L * sqrt(ALT_U_L))" }, { "fib4": 3.95, "alt_u_l": 40, "ast_u_l": 100, "formula": "fib4", "citation": { "id": "sterling-2006", "doi": "10.1002/hep.21172", "title": "Development of a simple noninvasive index to predict significant fibrosis in patients with HIV/HCV coinfection", "source": "Hepatology. 2006;43(6):1317-1325", "authors": "Sterling RK, Lissen E, Clumeck N, et al." }, "age_years": 50, "disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.", "sterling_band": "high", "platelets_10e9_l": 200, "formula_expression": "FIB-4 = (age_years * AST_U_L) / (platelets_10e9_L * sqrt(ALT_U_L))" } ] } } ``` ## More - Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fib-4-fibrosis-index-calculator-753fb585/health.json - [Zero catalog index](https://www.zero.xyz/llms.txt) - [Other services from api.magentlab.com](https://www.zero.xyz/host/api.magentlab.com/llms.txt)