# Steinhart AHF probability (2009) Steinhart AHF Status: LIVE Price: $0.005 USDC `GET /api/calc/steinhart` HTML: https://magentlab.com/docs/steinhart Markdown: https://magentlab.com/docs/steinhart.md Not a medical device. Not a diagnosis, dose, or listing recommendation. ## What it computes Compute the Steinhart 2009 Equation 1 probability of acute heart failure from caller-assigned age, clinician pretest probability, and NT-proBNP in pg/mL. ## When to use When an agent has Steinhart 2009 age, clinician pretest probability, and NT-proBNP in pg/mL and needs Equation 1 Pr(AHF) from the unrounded probability plus the published ≤0.20 and ≥0.80 flags, not a diuretic or admission order. ## When not to use - Not a medical device. Not a diagnosis. Not a diuretic order or an admission order. magent does not assay NT-proBNP or assign pretest probability. - Steinhart 2009 Equation 1 only. NT-proBNP is pg/mL, not pmol/L. magent does not convert units. - pretest_probability is caller-assigned as a fraction 0-1; values above 1 through 100 are treated as percent. magent does not examine the patient. - ahf_le_0_20 and ahf_ge_0_80 are the published model treatment thresholds (Pr(AHF) ≤0.20 and ≥0.80). magent does not invent intermediate bands. - estimated_probability_percent is a population probability from the unrounded Equation 1 value, not an individual outcome. ## Formula ``` Pr(AHF) = 1 / (1 + exp(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml))); pretest is clinician pretest probability as a fraction 0-1 (0-100 percent is divided by 100); NT-proBNP is pg/mL; logit = -(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml)), 2 decimals; estimated_probability_percent = 100 * Pr(AHF) from the unrounded probability, 2 decimals; ahf_le_0_20 is true when Pr(AHF) <= 0.20; ahf_ge_0_80 is true when Pr(AHF) >= 0.80 (Steinhart 2009) ``` ## Citation [Improving the Diagnosis of Acute Heart Failure Using a Validated Prediction Model](https://doi.org/10.1016/j.jacc.2009.05.065) Steinhart B, Thorpe KE, Bayoumi AM, Moe G, Januzzi JL Jr, Mazer CD J Am Coll Cardiol. 2009;54(16):1515-1521 DOI: [10.1016/j.jacc.2009.05.065](https://doi.org/10.1016/j.jacc.2009.05.065) ## Worked example ### Age 70, pretest 0.50, NT-proBNP 1000 pg/mL Given: `age=70, nt_probnp_pg_ml=1000, pretest_probability=0.50` 1. pretest 0.50 is a fraction (50 percent also enters as 0.50) 2. log10(1000) = 3 3. inner = 1.801 - 0.011*70 - 5.914*0.50 - 0.822*3 4. Pr(AHF) = 1 / (1 + exp(inner)) from the unrounded inner 5. estimated_probability_percent = 100 * Pr(AHF), 2 decimals 6. ahf_ge_0_80 is true when Pr(AHF) >= 0.80; ahf_le_0_20 is true when Pr(AHF) <= 0.20 (Steinhart 2009) ### Same row with pretest 50 percent Given: `age=70, nt_probnp_pg_ml=1000, pretest_probability=50` 1. pretest 50 is greater than 1 so it is divided by 100 → 0.50 2. Equation 1 matches the fraction-0.50 row; magent does not assay NT-proBNP ## Also searched as - Steinhart AHF model - Steinhart NT-proBNP probability - acute heart failure undifferentiated dyspnea - clinician pretest NT-proBNP AHF - Steinhart 2009 JACC AHF - post-test probability acute heart failure - NT-proBNP age pretest AHF ## Parameters - `age` (integer, required): Age in years, integer 18-100. Steinhart 2009 Equation 1 coefficient -0.011 per year. magent does not read an identity document. - `pretest_probability` (number, required): 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. - `nt_probnp_pg_ml` (number, required): NT-proBNP in pg/mL (5-35000). Enters as log10. Not pmol/L; magent does not convert units or assay NT-proBNP. ## Bulk (POST) POST the same path with a JSON items array. The first item is the GET unit; each additional item is $0.002. Invalid items return HTTP 400 before settlement. Method: `POST /api/calc/steinhart` Max items: 25 Price: unit_amount + extra_item_amount * (n - 1) (unit 5000 atomic, extra 2000 atomic) Status: PREVIEW - 1 to 25 items. Each item uses the same keys as the GET query parameters. - POST of 1 item costs the same as GET. Lists longer than 25: chunk into multiple POSTs. Extra items still execute; do not pad dummy rows. - The first invalid item fails the whole request (index in the 400 JSON). You are not charged. - HTTP 200 is {count, path, items}. Each items[i] is the GET 200 body for that row. - Catalog misses (empty matches, found=false) stay paid 200s inside that slot. - x402 resource URL is this path plus n and body_sha256. Browsers that prefer text/html get the same paywall as GET; Pay retries POST with the same items. Example request: ```json { "items": [ { "age": "70", "nt_probnp_pg_ml": "1000", "pretest_probability": "0.50" }, { "age": "70", "nt_probnp_pg_ml": "1000", "pretest_probability": "0.50" } ] } ``` Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/steinhart Example 200: ```json { "count": 2, "path": "/api/calc/steinhart", "items": [ { "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.", "citation": { "authors": "Steinhart B, Thorpe KE, Bayoumi AM, Moe G, Januzzi JL Jr, Mazer CD", "doi": "10.1016/j.jacc.2009.05.065", "id": "steinhart-2009", "pmid": "19815125", "source": "J Am Coll Cardiol. 2009;54(16):1515-1521", "title": "Improving the Diagnosis of Acute Heart Failure Using a Validated Prediction Model" }, "formula": "steinhart", "formula_expression": "Pr(AHF) = 1 / (1 + exp(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml))); pretest is clinician pretest probability as a fraction 0-1 (0-100 percent is divided by 100); NT-proBNP is pg/mL; logit = -(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml)), 2 decimals; estimated_probability_percent = 100 * Pr(AHF) from the unrounded probability, 2 decimals; ahf_le_0_20 is true when Pr(AHF) <= 0.20; ahf_ge_0_80 is true when Pr(AHF) >= 0.80 (Steinhart 2009)", "age_years": 70, "estimated_probability_percent": 98.78, "logit": 4.39, "ahf_ge_0_80": true, "ahf_le_0_20": false, "nt_probnp_pg_ml": 1.0e3, "pretest_probability": 0.5 }, { "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.", "citation": { "authors": "Steinhart B, Thorpe KE, Bayoumi AM, Moe G, Januzzi JL Jr, Mazer CD", "doi": "10.1016/j.jacc.2009.05.065", "id": "steinhart-2009", "pmid": "19815125", "source": "J Am Coll Cardiol. 2009;54(16):1515-1521", "title": "Improving the Diagnosis of Acute Heart Failure Using a Validated Prediction Model" }, "formula": "steinhart", "formula_expression": "Pr(AHF) = 1 / (1 + exp(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml))); pretest is clinician pretest probability as a fraction 0-1 (0-100 percent is divided by 100); NT-proBNP is pg/mL; logit = -(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml)), 2 decimals; estimated_probability_percent = 100 * Pr(AHF) from the unrounded probability, 2 decimals; ahf_le_0_20 is true when Pr(AHF) <= 0.20; ahf_ge_0_80 is true when Pr(AHF) >= 0.80 (Steinhart 2009)", "age_years": 70, "estimated_probability_percent": 98.78, "logit": 4.39, "ahf_ge_0_80": true, "ahf_le_0_20": false, "nt_probnp_pg_ml": 1.0e3, "pretest_probability": 0.5 } ] } ``` ## Response fields - `formula` (string): steinhart - `formula_expression` (string): Steinhart 2009 Equation 1 Pr(AHF) and published 0.20 / 0.80 flags - `age_years` (integer): Age in years used in Equation 1 - `pretest_probability` (number): Clinician pretest probability as a fraction 0-1 used in Equation 1 - `nt_probnp_pg_ml` (number): NT-proBNP in pg/mL used in log10 - `logit` (number): Log-odds of AHF, 2 decimal places: -(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(NT-proBNP)). Percent uses the unrounded probability. - `estimated_probability_percent` (number): 100 * Pr(AHF) from the unrounded Equation 1 probability, 2 decimals. A population probability, not a diagnosis or admission order. - `ahf_le_0_20` (boolean): true when Pr(AHF) <= 0.20 (Steinhart 2009 published rule-out threshold). Not an invented band. - `ahf_ge_0_80` (boolean): true when Pr(AHF) >= 0.80 (Steinhart 2009 published rule-in threshold). Not an invented band. - `citation` (object): Steinhart 2009 citation - `disclaimer` (string): Not-a-device notice ## Example JSON Frozen fixture. Not a live lookup. ```json { "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.", "citation": { "authors": "Steinhart B, Thorpe KE, Bayoumi AM, Moe G, Januzzi JL Jr, Mazer CD", "doi": "10.1016/j.jacc.2009.05.065", "id": "steinhart-2009", "pmid": "19815125", "source": "J Am Coll Cardiol. 2009;54(16):1515-1521", "title": "Improving the Diagnosis of Acute Heart Failure Using a Validated Prediction Model" }, "formula": "steinhart", "formula_expression": "Pr(AHF) = 1 / (1 + exp(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml))); pretest is clinician pretest probability as a fraction 0-1 (0-100 percent is divided by 100); NT-proBNP is pg/mL; logit = -(1.801 - 0.011*age - 5.914*pretest - 0.822*log10(nt_probnp_pg_ml)), 2 decimals; estimated_probability_percent = 100 * Pr(AHF) from the unrounded probability, 2 decimals; ahf_le_0_20 is true when Pr(AHF) <= 0.20; ahf_ge_0_80 is true when Pr(AHF) >= 0.80 (Steinhart 2009)", "age_years": 70, "estimated_probability_percent": 98.78, "logit": 4.39, "ahf_ge_0_80": true, "ahf_le_0_20": false, "nt_probnp_pg_ml": 1.0e3, "pretest_probability": 0.5 } ``` ## Errors - HTTP 400 `invalid_steinhart`: Steinhart AHF needs 2009 age, clinician pretest probability, and NT-proBNP in published ranges. Returned before settlement; you are not charged. - HTTP 400 `invalid_items`: POST body must be a JSON object with only an items array Returned before settlement; you are not charged. - HTTP 400 `invalid_item_count`: items must be an array of 1 to 25 objects Returned before settlement; you are not charged. - HTTP 400 `invalid_item`: each items entry must be a JSON object Returned before settlement; you are not charged. Shared HTTP 402 and 503: https://magentlab.com/docs/payments ## Related tools - [H2FPEF](https://magentlab.com/docs/h2fpef) — Sum the Reddy 2018 H2FPEF points score (six components, max 9) and return score and max_score only. - [ADHERE](https://magentlab.com/docs/adhere) — Apply the Fonarow 2005 ADHERE classification and regression tree for in-hospital mortality risk in acutely decompensated heart failure from admission BUN, systolic blood pressure, and serum creatinine. ## Payment Unpaid requests return HTTP 402 even if query parameters or POST items are missing or invalid, so CDP and agents can index the path. After a PAYMENT-SIGNATURE, invalid params return HTTP 400 JSON before settlement. magent does not charge. Fix the params, then request a new 402 quote for that complete URL. Catalog misses (empty matches, found=false) are valid paid 200s. - GET the tool with Accept: application/json (do not send Accept: text/html unless you want the human paywall). - HTTP 402 means you have not paid. Decode the base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote. - Sign accepts[0] (exact, EIP-3009) with validBefore = now + maxTimeoutSeconds (600 seconds), or accepts[1] (batch-settlement deposit/voucher) on product GET. Ping and POST {items} stay exact. Magent retries transient facilitator 429/5xx before answering. - Retry the same URL with PAYMENT-SIGNATURE (base64 JSON of accepted and payload). Magent attaches canonical extensions.bazaar on CDP verify/settle; echoing 402 bazaar is optional. - Success is HTTP 200 JSON plus PAYMENT-RESPONSE. exact settles before the tool. batch-settlement verifies (and deposit-settles) before the tool and commits the charge after HTTP 2xx. HTTP 503: retry the same PAYMENT-SIGNATURE. Mint a new exact nonce only after a new HTTP 402. - offered `exact` on eip155:8453: Fixed-price USDC on Base. The buyer authorizes the advertised amount (EIP-3009). magent settles before the tool runs (paymentFlow upfront). extra.assetTransferMethod=eip3009 extra.paymentFlow=upfront. - offered `batch-settlement` on eip155:8453: Payment-channel vouchers claimed later in batches. Exact stays accepts[0]. Same-path POST {items} is still exact. extra.assetTransferMethod=eip3009 extra.paymentFlow=authorization. - not offered `upto`: Not offered. Usage-based: buyer authorizes a ceiling, seller settles the actual amount after work. Reserved for a future metered tool. Not for current calculators or code search. Same-path POST {items} is still scheme exact: one EIP-3009 authorization for GET unit plus $0.002 per extra item. That is not x402 batch-settlement (payment channels / vouchers). Shared HTTP 402 and 503 table: https://magentlab.com/docs/payments Stdio MCP (one process per host): https://magentlab.com/docs/mcp ## Guarantees - HTTP 402 is unpaid, including a missing query. After PAYMENT-SIGNATURE, invalid parameters return HTTP 400 before settlement. You are not charged. HTTP 402 never includes the tool JSON. - exact: settlement finishes before the tool (paymentFlow upfront). batch-settlement: verify/deposit before the tool; chargedCumulativeAmount commits after HTTP 2xx. Uncertain or failed settlement fails closed (HTTP 503). Retry the same PAYMENT-SIGNATURE. - HTTP 402 is unpaid only. Do not sign a second authorization because of a 503. - Execution is timeout-bounded and concurrency-capped. - Calculator inputs are stored encrypted for allowlisted operators (Magent Console). They are not in public logs, SSH lookups, catalog, or rollups. Request logs store path without query.