Kidney · LIVE

CKiD U25 eGFR

Compute Pierce 2021 CKiD U25 eGFR in mL/min/1.73m2 from age-dependent K with height and creatinine, cystatin C, or both.

LIVE $0.005 USDC GET /api/calc/ckid_u25

Markdown: /docs/ckid-u25.md · Canonical: https://magentlab.com/docs/ckid-u25

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

What it computes

Compute Pierce 2021 CKiD U25 eGFR in mL/min/1.73m2 from age-dependent K with height and creatinine, cystatin C, or both.

When to use

When an agent needs the CKiD under-25 eGFR for ages 1–25 and must not invent Schwartz 2009 bedside 0.413, adult CKD-EPI, or a CKD stage.

When not to use

• Not a medical device. magent does not dose drugs.
• Validated for ages 1–25 years (CKiD under-25 equations). Not an adult CKD-EPI equation.
• This is the Pierce 2021 age-dependent K model (creatinine, cystatin C, or the average of both). It is not the Schwartz 2009 bedside 0.413 formula and not the constant-K CKiD models.
• Does not assign CKD stages.

Formula

egfr_cr = K_cr * (height_m / creatinine_mg_dl); egfr_cys = K_cys * (1 / cystatin_c_mg_l); combined = (egfr_cr + egfr_cys) / 2 when both markers; K_cr and K_cys are Pierce 2021 Table 2 age-dependent (not constant-K models); height in meters; ages 1-25

Citation

Title

Age- and sex-dependent clinical equations to estimate glomerular filtration rates in children and young adults with chronic kidney disease

Authors

Pierce CB, Muñoz A, Ng DK, Warady BA, Furth SL, Schwartz GJ

Source

Kidney Int. 2021;99(4):948-956

DOI

10.1016/j.kint.2020.10.047

Worked example

Also searched as

• CKiD U25
• pediatric eGFR
• CKiD under 25
• Pierce 2021 eGFR
• age-dependent K eGFR
• cystatin C pediatric eGFR
• CKiD creatinine cystatin

Try

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

/api/calc/ckid_u25?age_years=10&sex=male&height_cm=140&creatinine_mg_dl=1.0

Full URL: https://api.magentlab.com/api/calc/ckid_u25?age_years=10&sex=male&height_cm=140&creatinine_mg_dl=1.0

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/ckid_u25?age_years=10&sex=male&height_cm=140&creatinine_mg_dl=1.0"

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/ckid_u25 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": [
    {
      "age_years": "10",
      "creatinine_mg_dl": "1.0",
      "height_cm": "140",
      "sex": "male"
    },
    {
      "age_years": "10",
      "creatinine_mg_dl": "1.0",
      "height_cm": "140",
      "sex": "male"
    }
  ]
}

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/ckid_u25",
  "items": [
    {
      "units": "mL/min/1.73m2",
      "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": "Pierce CB, Muñoz A, Ng DK, Warady BA, Furth SL, Schwartz GJ",
        "doi": "10.1016/j.kint.2020.10.047",
        "id": "pierce-2021-ckid-u25",
        "pmid": "33301749",
        "source": "Kidney Int. 2021;99(4):948-956",
        "title": "Age- and sex-dependent clinical equations to estimate glomerular filtration rates in children and young adults with chronic kidney disease"
      },
      "formula": "ckid_u25_cr",
      "formula_expression": "egfr_cr = K_cr * (height_m / creatinine_mg_dl); egfr_cys = K_cys * (1 / cystatin_c_mg_l); combined = (egfr_cr + egfr_cys) / 2 when both markers; K_cr and K_cys are Pierce 2021 Table 2 age-dependent (not constant-K models); height in meters; ages 1-25",
      "age_years": 10.0,
      "creatinine_mg_dl": 1.0,
      "sex": "male",
      "height_cm": 140.0,
      "egfr_ml_min_1_73m2": 53.7,
      "k_cr": 38.3834
    },
    {
      "units": "mL/min/1.73m2",
      "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": "Pierce CB, Muñoz A, Ng DK, Warady BA, Furth SL, Schwartz GJ",
        "doi": "10.1016/j.kint.2020.10.047",
        "id": "pierce-2021-ckid-u25",
        "pmid": "33301749",
        "source": "Kidney Int. 2021;99(4):948-956",
        "title": "Age- and sex-dependent clinical equations to estimate glomerular filtration rates in children and young adults with chronic kidney disease"
      },
      "formula": "ckid_u25_cr",
      "formula_expression": "egfr_cr = K_cr * (height_m / creatinine_mg_dl); egfr_cys = K_cys * (1 / cystatin_c_mg_l); combined = (egfr_cr + egfr_cys) / 2 when both markers; K_cr and K_cys are Pierce 2021 Table 2 age-dependent (not constant-K models); height in meters; ages 1-25",
      "age_years": 10.0,
      "creatinine_mg_dl": 1.0,
      "sex": "male",
      "height_cm": 140.0,
      "egfr_ml_min_1_73m2": 53.7,
      "k_cr": 38.3834
    }
  ]
}

Response

Example JSON

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

{
  "units": "mL/min/1.73m2",
  "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": "Pierce CB, Muñoz A, Ng DK, Warady BA, Furth SL, Schwartz GJ",
    "doi": "10.1016/j.kint.2020.10.047",
    "id": "pierce-2021-ckid-u25",
    "pmid": "33301749",
    "source": "Kidney Int. 2021;99(4):948-956",
    "title": "Age- and sex-dependent clinical equations to estimate glomerular filtration rates in children and young adults with chronic kidney disease"
  },
  "formula": "ckid_u25_cr",
  "formula_expression": "egfr_cr = K_cr * (height_m / creatinine_mg_dl); egfr_cys = K_cys * (1 / cystatin_c_mg_l); combined = (egfr_cr + egfr_cys) / 2 when both markers; K_cr and K_cys are Pierce 2021 Table 2 age-dependent (not constant-K models); height in meters; ages 1-25",
  "age_years": 10.0,
  "creatinine_mg_dl": 1.0,
  "sex": "male",
  "height_cm": 140.0,
  "egfr_ml_min_1_73m2": 53.7,
  "k_cr": 38.3834
}

Client errors (HTTP 400)

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

Related tools

• Schwartz 2009 eGFR — Compute the 2009 Schwartz bedside CKiD eGFR in mL/min/1.73m2 from height and serum creatinine.
• CKD-EPI 2021 eGFR — Compute race-free CKD-EPI 2021 creatinine eGFR in mL/min/1.73m2.
• KFRE — Compute 2-year and 5-year risk of kidney failure (dialysis or preemptive transplant) from the Tangri 2011 4-variable Kidney Failure Risk Equation (age, sex, eGFR, urine ACR).

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.