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 — Compute race-free CKD-EPI 2021 creatinine eGFR in mL/min/1.73m2.
• FENa — Compute fractional excretion of sodium from plasma and urine sodium and creatinine using Espinel 1976.
• Mosteller BSA — Compute Mosteller body surface area in m^2 from height and weight.

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.