# Steinhart 2009 Acute Heart Failure Probability Calculator

> Steinhart 2009 Acute Heart Failure Probability 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).

Calculates the probability of acute heart failure using the Steinhart 2009 Equation 1 logistic model from age, clinician pretest probability, and NT-proBNP level, with rule-out and rule-in flags.

## Facts

- Endpoint: GET https://api.magentlab.com/api/calc/steinhart
- 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/steinhart-2009-acute-heart-failure-probability-calculator-4cf7989e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_O7194l3wB0LAZ5_qE_F2w

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 steinhart-2009-acute-heart-failure-probability-calculator-4cf7989e
```

Example prompt: Using the Steinhart 2009 model, what's the probability this 72-year-old patient has acute heart failure? The clinician's pretest probability is 0.45 and the NT-proBNP came back at 3200 pg/mL.

## When to prefer this

Use this endpoint when you need a validated, published logistic model (Steinhart 2009 Equation 1) specifically for acute heart failure probability combining NT-proBNP, clinician pretest probability, and age. Prefer this over generic biomarker lookup tools when you need an interpreted probability with rule-in/rule-out decision thresholds. Not appropriate for chronic heart failure risk scoring (see MAGGIC) or ACS probability (see T-MACS).

## Known failure modes

- Missing required parameters (age, pretest_probability, or nt_probnp_pg_ml) returns a validation error
- Age outside 18-100 range may be rejected or produce out-of-validation-range results
- NT-proBNP outside 5-35000 pg/mL range may produce unreliable results
- Pretest probability provided in percent (e.g. 45) is auto-divided by 100; misuse of scale can yield unexpected results
- NT-proBNP provided in pmol/L instead of pg/mL will silently produce incorrect probabilities since no unit conversion is performed
- Payment failure via x402 protocol returns 402 status with no computation

## How this service works

Steinhart 2009 Equation 1 probability of acute heart failure from caller-assigned age, clinician pretest probability (fraction 0-1 or 0-100 percent), and NT-proBNP in pg/mL. Returns estimated_probability_percent from the unrounded probability plus published ≤0.20 rule-out and ≥0.80 rule-in flags. Not a diagnosis, diuretic, or admission order. magent does not assay NT-proBNP.

## Output

Returns an estimated_probability_percent representing the unrounded Steinhart 2009 Equation 1 logistic model output, plus boolean flags indicating whether the probability meets the published ≤0.20 rule-out or ≥0.80 rule-in thresholds for acute heart failure. Does not provide a diagnosis or clinical order.

## 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",
      "pretest_probability",
      "nt_probnp_pg_ml"
     ],
     "properties": {
      "age": {
       "type": "integer",
       "description": "Age in years, integer 18-100. Steinhart 2009 Equation 1 coefficient -0.011 per year. magent does not read an identity document."
      },
      "nt_probnp_pg_ml": {
       "type": "number",
       "description": "NT-proBNP in pg/mL (5-35000). Enters as log10. Not pmol/L; magent does not convert units or assay NT-proBNP."
      },
      "pretest_probability": {
       "type": "number",
       "description": "Caller-assigned clinician pretest probability of acute heart failure before NT-proBNP. Fraction 0-1, or 0-100 percent (values above 1 are divided by 100). 1 means certainty, not 1 percent. Steinhart 2009 coefficient -5.914 on the fraction. magent does not assign pretest probability or examine the patient."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/steinhart-2009-acute-heart-failure-probability-calculator-4cf7989e/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)