# CKD-EPI 2021 eGFR

Status: LIVE
Price: $0.005 USDC
`GET /api/calc/egfr_ckd_epi`
HTML: https://magentlab.com/docs/egfr
Markdown: https://magentlab.com/docs/egfr.md

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

## What it computes

Compute race-free CKD-EPI 2021 creatinine eGFR in mL/min/1.73m2.

## When to use

When an agent must not guess kidney function from a language model and needs the published 2021 equation.

## When not to use

- Not a treatment recommendation and not a dosing recommendation.
- Creatinine-only 2021 equation. No race coefficient. Cystatin C is not accepted.
- Does not apply pediatric equations.

## Formula

```
142 * min(Scr/κ,1)^α * max(Scr/κ,1)^(-1.200) * 0.9938^age * (1.012 if female)
```

## Citation

New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race
Inker LA, Eneanya ND, Coresh J, et al.
N Engl J Med. 2021;385(19):1737-1749
DOI: [10.1056/NEJMoa2102953](https://doi.org/10.1056/NEJMoa2102953)

## Worked example

### Scr 1.1, age 65, female

Given: `age=65, creatinine_mg_dl=1.1, sex=female`

1. κ=0.7, α=-0.241, sex factor=1.012
2. Evaluate 142 * min(Scr/κ,1)^α * max(Scr/κ,1)^(-1.200) * 0.9938^age * 1.012
3. Round to 1 decimal


## Parameters

- `creatinine_mg_dl` (number, optional): Serum creatinine in mg/dL. Provide this or creatinine_umol_l.
- `creatinine_umol_l` (number, optional): Serum creatinine in µmol/L. Converted as mg/dL = µmol/L / 88.42.
- `age` (integer, required): Age in years (18-120). CKD-EPI 2021 is validated in adults.
- `sex` (string, required): Sex used by the published equation. female or male.

## Bulk (POST)

POST the same path with a JSON items array. Price is n times the GET unit. Invalid items return HTTP 400 before settlement.

Method: `POST /api/calc/egfr_ckd_epi`
Max items: 25
Price: unit_amount * n (unit 5000 atomic)
Status: PREVIEW

- 1 to 25 items. Each item uses the same keys as the GET query parameters.
- 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": "65",
      "creatinine_mg_dl": "1.1",
      "sex": "female"
    },
    {
      "age": "65",
      "creatinine_mg_dl": "1.1",
      "sex": "female"
    }
  ]
}
```

Human paywall (two-item fixture): https://api.magentlab.com/paywall/bulk/egfr

Example 200:

```json
{
  "count": 2,
  "path": "/api/calc/egfr_ckd_epi",
  "items": [
    {
      "units": "mL/min/1.73m2",
      "disclaimer": "Not a medical device. Deterministic published-formula or coded-ontology output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Inker LA, Eneanya ND, Coresh J, et al.",
        "doi": "10.1056/NEJMoa2102953",
        "id": "inker-2021",
        "source": "N Engl J Med. 2021;385(19):1737-1749",
        "title": "New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race"
      },
      "formula": "ckd_epi_2021_creatinine",
      "formula_expression": "142 * min(Scr/κ,1)^α * max(Scr/κ,1)^(-1.200) * 0.9938^age * (1.012 if female)",
      "age_years": 65,
      "creatinine_mg_dl": 1.1,
      "egfr_ml_min_1_73m2": 55.8,
      "sex": "female"
    },
    {
      "units": "mL/min/1.73m2",
      "disclaimer": "Not a medical device. Deterministic published-formula or coded-ontology output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
      "citation": {
        "authors": "Inker LA, Eneanya ND, Coresh J, et al.",
        "doi": "10.1056/NEJMoa2102953",
        "id": "inker-2021",
        "source": "N Engl J Med. 2021;385(19):1737-1749",
        "title": "New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race"
      },
      "formula": "ckd_epi_2021_creatinine",
      "formula_expression": "142 * min(Scr/κ,1)^α * max(Scr/κ,1)^(-1.200) * 0.9938^age * (1.012 if female)",
      "age_years": 65,
      "creatinine_mg_dl": 1.1,
      "egfr_ml_min_1_73m2": 55.8,
      "sex": "female"
    }
  ]
}
```

## Response fields

- `formula` (string): ckd_epi_2021_creatinine
- `formula_expression` (string): Exact expression used
- `creatinine_mg_dl` (number): Normalized creatinine
- `age_years` (integer): Age used in the equation
- `sex` (string): female or male
- `egfr_ml_min_1_73m2` (number): Estimated GFR, 1 decimal place
- `units` (string): mL/min/1.73m2
- `citation` (object): NEJM 2021 citation
- `disclaimer` (string): Not-a-device notice

## Example JSON

Frozen fixture. Not a live lookup.

```json
{
  "units": "mL/min/1.73m2",
  "disclaimer": "Not a medical device. Deterministic published-formula or coded-ontology output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
  "citation": {
    "authors": "Inker LA, Eneanya ND, Coresh J, et al.",
    "doi": "10.1056/NEJMoa2102953",
    "id": "inker-2021",
    "source": "N Engl J Med. 2021;385(19):1737-1749",
    "title": "New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race"
  },
  "formula": "ckd_epi_2021_creatinine",
  "formula_expression": "142 * min(Scr/κ,1)^α * max(Scr/κ,1)^(-1.200) * 0.9938^age * (1.012 if female)",
  "age_years": 65,
  "creatinine_mg_dl": 1.1,
  "egfr_ml_min_1_73m2": 55.8,
  "sex": "female"
}
```

## Errors

- HTTP 400 `invalid_creatinine`: creatinine_mg_dl (0.1-20) or creatinine_umol_l (9-1768) is required Returned before settlement; you are not charged.
- HTTP 400 `invalid_age`: age must be an integer from 18 to 120 Returned before settlement; you are not charged.
- HTTP 400 `invalid_sex`: sex must be female or male 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.
- HTTP 402 `payment_required`: Missing or invalid PAYMENT-SIGNATURE; decode the PAYMENT-REQUIRED header
- HTTP 409 `payment_in_progress`: The same authorization nonce is already being settled; retry shortly
- HTTP 429 `rate_limited`: Too many requests from this client
- HTTP 503 `settlement_uncertain`: Settlement is unconfirmed; retry with the same PAYMENT-SIGNATURE
- HTTP 503 `facilitator_unavailable`: Payment facilitator unavailable
- HTTP 503 `facilitator_misconfigured`: Payment facilitator is not configured
- HTTP 503 `facilitator_unauthorized`: Payment facilitator rejected credentials
- HTTP 503 `ledger_unavailable`: Payment ledger unavailable
- HTTP 503 `payment_unavailable`: Payment processing unavailable

## Related tools

- [Cockcroft–Gault CrCl](https://magentlab.com/docs/crcl) — Compute Cockcroft–Gault creatinine clearance in mL/min using total body weight.

## Also searched as

- CKD-EPI 2021
- race-free eGFR
- Inker eGFR
- creatinine GFR

## Payment

Required query parameters must be present and valid. 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.

## Guarantees

- Invalid query parameters return HTTP 400 before settlement. You are not charged.
- Settlement finishes before the tool executes. Uncertain settlement fails closed (HTTP 503).
- Execution is timeout-bounded and concurrency-capped.
- Calculator inputs are not persisted. Request logs store path without query.