Kidney · LIVE

NRPE

Compute the Rao 2021 natriuretic response prediction equation from a spot urine sample ~2 h after IV loop diuretic using caller-assigned eGFR and BSA, serum and urine creatinine, and urine sodium.

LIVE $0.005 USDC GET /api/calc/nrpe

Markdown: /docs/nrpe.md · Canonical: https://magentlab.com/docs/nrpe

Not a medical device. Not a diagnosis, dose, or listing recommendation.

What it computes

Compute the Rao 2021 natriuretic response prediction equation from a spot urine sample ~2 h after IV loop diuretic using caller-assigned eGFR and BSA, serum and urine creatinine, and urine sodium.

When to use

When an agent needs published Rao 2021 predicted Na and urine output and must not invent a diuretic order, CKD-EPI eGFR, or Du Bois BSA.

When not to use

• Not a medical device. Not a diuretic order and not a diagnosis of diuretic resistance.
• magent does not compute eGFR or BSA. The caller supplies egfr_ml_min_1_73m2 (5-200) and bsa_m2 (0.4-3.5). The paper used CKD-EPI and Du Bois; magent does not implement race-based 2009 CKD-EPI.
• The spot urine sample is caller-timed (~2 h after IV loop diuretic in Rao 2021). magent does not time collection or assay labs. 100-150 mmol is unlabeled in the paper.

Formula

na_output_mmol = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25 * (urine_sodium_mmol_l / 1000); urine_output_ml = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25

Citation

Title

Natriuretic Equation to Predict Loop Diuretic Response in Patients With Heart Failure

Authors

Rao VS, Ivey-Miranda JB, Cox ZL, et al.

Source

J Am Coll Cardiol. 2021;77(6):695-708

DOI

10.1016/j.jacc.2020.12.022

Worked example

Also searched as

• natriuretic response prediction equation
• Rao natriuretic equation
• loop diuretic sodium output
• predicted natriuretic response
• Testani natriuretic equation
• spot urine after loop diuretic
• natriuretic equation heart failure

Try

Opens the live endpoint. Unpaid browser requests show the paywall; agents should send Accept: application/json.

/api/calc/nrpe?egfr_ml_min_1_73m2=80&bsa_m2=1.73&creatinine_mg_dl=1.0&urine_creatinine_mg_dl=25&urine_sodium_mmol_l=90

Full URL: https://api.magentlab.com/api/calc/nrpe?egfr_ml_min_1_73m2=80&bsa_m2=1.73&creatinine_mg_dl=1.0&urine_creatinine_mg_dl=25&urine_sodium_mmol_l=90

Call

Expect HTTP 402 until you retry with PAYMENT-SIGNATURE. Incomplete query params return HTTP 400 before any quote or charge.

curl -i -H "Accept: application/json" "https://api.magentlab.com/api/calc/nrpe?egfr_ml_min_1_73m2=80&bsa_m2=1.73&creatinine_mg_dl=1.0&urine_creatinine_mg_dl=25&urine_sodium_mmol_l=90"

Parameters

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.

POST /api/calc/nrpe Max 25 unit_amount + extra_item_amount * (n - 1) extra $0.002 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 (fixture)

{
  "items": [
    {
      "bsa_m2": "1.73",
      "creatinine_mg_dl": "1.0",
      "egfr_ml_min_1_73m2": "80",
      "urine_creatinine_mg_dl": "25",
      "urine_sodium_mmol_l": "90"
    },
    {
      "bsa_m2": "1.73",
      "creatinine_mg_dl": "1.0",
      "egfr_ml_min_1_73m2": "80",
      "urine_creatinine_mg_dl": "25",
      "urine_sodium_mmol_l": "90"
    }
  ]
}

Open bulk paywall →

Opens a two-item fixture on the API host. Unpaid browsers get the same MetaMask paywall as GET; Pay retries POST with those items.

Example 200 (fixture)

{
  "count": 2,
  "path": "/api/calc/nrpe",
  "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": "Rao VS, Ivey-Miranda JB, Cox ZL, et al.",
        "doi": "10.1016/j.jacc.2020.12.022",
        "id": "rao-2021",
        "pmid": "33573739",
        "source": "J Am Coll Cardiol. 2021;77(6):695-708",
        "title": "Natriuretic Equation to Predict Loop Diuretic Response in Patients With Heart Failure"
      },
      "formula": "nrpe",
      "formula_expression": "na_output_mmol = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25 * (urine_sodium_mmol_l / 1000); urine_output_ml = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25",
      "creatinine_mg_dl": 1.0,
      "bsa_m2": 1.73,
      "egfr_ml_min_1_73m2": 80.0,
      "urine_creatinine_mg_dl": 25.0,
      "urine_sodium_mmol_l": 90.0,
      "excellent_response": false,
      "na_output_mmol": 56.2,
      "poor_response": false,
      "suboptimal_response": true,
      "urine_output_ml": 624.0
    },
    {
      "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": "Rao VS, Ivey-Miranda JB, Cox ZL, et al.",
        "doi": "10.1016/j.jacc.2020.12.022",
        "id": "rao-2021",
        "pmid": "33573739",
        "source": "J Am Coll Cardiol. 2021;77(6):695-708",
        "title": "Natriuretic Equation to Predict Loop Diuretic Response in Patients With Heart Failure"
      },
      "formula": "nrpe",
      "formula_expression": "na_output_mmol = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25 * (urine_sodium_mmol_l / 1000); urine_output_ml = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25",
      "creatinine_mg_dl": 1.0,
      "bsa_m2": 1.73,
      "egfr_ml_min_1_73m2": 80.0,
      "urine_creatinine_mg_dl": 25.0,
      "urine_sodium_mmol_l": 90.0,
      "excellent_response": false,
      "na_output_mmol": 56.2,
      "poor_response": false,
      "suboptimal_response": true,
      "urine_output_ml": 624.0
    }
  ]
}

Response

Example JSON

Machine form of the same example. Frozen fixture. Not a live lookup.

{
  "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": "Rao VS, Ivey-Miranda JB, Cox ZL, et al.",
    "doi": "10.1016/j.jacc.2020.12.022",
    "id": "rao-2021",
    "pmid": "33573739",
    "source": "J Am Coll Cardiol. 2021;77(6):695-708",
    "title": "Natriuretic Equation to Predict Loop Diuretic Response in Patients With Heart Failure"
  },
  "formula": "nrpe",
  "formula_expression": "na_output_mmol = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25 * (urine_sodium_mmol_l / 1000); urine_output_ml = egfr_ml_min_1_73m2 * (bsa_m2 / 1.73) * (creatinine_mg_dl / urine_creatinine_mg_dl) * 60 * 3.25",
  "creatinine_mg_dl": 1.0,
  "bsa_m2": 1.73,
  "egfr_ml_min_1_73m2": 80.0,
  "urine_creatinine_mg_dl": 25.0,
  "urine_sodium_mmol_l": 90.0,
  "excellent_response": false,
  "na_output_mmol": 56.2,
  "poor_response": false,
  "suboptimal_response": true,
  "urine_output_ml": 624.0
}

Client errors (HTTP 400)

Invalid params return 400 without charge. Shared HTTP 402 and 503 meanings: Payments.

Related tools

• CKD-EPI 2021 eGFR — Agents must not invent eGFR from model memory. This endpoint computes published race-free CKD-EPI 2021 creatinine eGFR in mL/min/1.73m2; pay per request with x402 USDC on Base.
• FENa — Compute fractional excretion of sodium from plasma and urine sodium and creatinine using Espinel 1976.
• Mosteller BSA — Agents must not invent BSA from model memory. This endpoint computes published Mosteller body surface area in m^2 from height and weight; pay per request with x402 USDC on Base.

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. Unpaid valid requests return HTTP 402 with a base64 PAYMENT-REQUIRED header. HTTP 503 is not a new quote: retry the same PAYMENT-SIGNATURE. Full handshake and shared payment errors: Payments. Stdio MCP: /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.