Source: https://guthlabs.ai/docs/instruments/egfr-ckd-epi-2021-race-free/implementation/

instrument implementation / implementation-contract

# eGFR (CKD-EPI 2021, race-free) implementation

A source-bound implementation contract for eGFR (CKD-EPI 2021, race-free); deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-014

**Effect**: Computation or source lookup only

## Input and validation requirements

A serum creatinine input of exactly 0 causes the negative power 0^(-0.302), producing an undefined or non-finite result. The instrument should reject this input instead of assigning an eGFR or CKD stage.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "age_years": 40,
    "sex": "male",
    "serum_creatinine_mg_dL": 0.9
  },
  "expected_outputs": {
    "eGFR_mL_min_1_73m2": 110.73,
    "stage_label": "G1"
  },
  "working": "Male: k = 0.9, alpha = -0.302. SCr/k = 0.9/0.9 = 1. Therefore min(1,1)^(-0.302) = 1 and max(1,1)^(-1.200) = 1. Age factor = 0.9938^40 = 0.77976. eGFR = 142 × 1 × 1 × 0.77976 = 110.73 mL/min/1.73 m². Since 110.73 >= 90, the eGFR category is G1."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/egfr-ckd-epi-2021-race-free/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/egfr-ckd-epi-2021-race-free/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/egfr-ckd-epi-2021-race-free/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche4/tranche4-results.json`