# Previous eGFR Equations for Reference

**Glomerular filtration rate (GFR) estimating equations that include a race coefficient are provided for reference purposes only.**

NIDDK supports the National Kidney Foundation–American Society of Nephrology Task Force’s recommendation to calculate estimated GFR (eGFR) using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) estimating equations that do not include a race coefficient.

However, because the race-free equations may yield slightly different eGFR values compared to older equations, trends in eGFR should be assessed using results from a single equation. During the transition to the race-free equations, understanding how results from the older race-based equations compare to results using the race-free equations will allow patients and clinicians to better understand changes in eGFR over time, independent of changes caused by a transition in estimating equations.

It may be useful to reference information on the following race-based equations, for use in individuals ages 18 and older, when assessing eGFR results calculated prior to the transition to the race-free equations.

## Equations

NIDDK calculates eGFR using creatinine determinations that are traceable to an isotope dilution mass spectrometry (IDMS) reference measurement procedure and cystatin C determinations that are traceable to ERM-DA471_IFCC HUMAN SERUM (cystatin C) certified reference material.

### 2009 CKD-EPI Creatinine Equation

The 2009 CKD-EPI creatinine equation was the most commonly used eGFR equation in the United States at the time the race-free 2021 CKD-EPI equations were developed. The equation uses a 2-slope “spline” to model the relationship between GFR and age, sex, race, and serum creatinine.^{1} The equation can be calculated in conventional or SI units.

#### Conventional Units

The equation can be expressed as a single equation in conventional units:

**eGFR = 141 × min(SCr/κ, 1) ^{α} × max(SCr/κ, 1)^{-1.209} × 0.993^{Age} × 1.018 [if female] × 1.159 [if African American]**

Abbreviations/units

- eGFR = estimated GFR in mL/min/1.73 m
^{2} - SCr = standardized serum creatinine in mg/dL
- κ = 0.7 (females) or 0.9 (males)
- α = -0.329 (females) or -0.411 (males)
- min = indicates the minimum of SCr/κ or 1
- max = indicates the maximum of SCr/κ or 1
- age = years

Alternately, the equation can be expressed as a series of equations for different race, sex, and creatinine conditions, as shown in Table 1.

**Table 1. 2009 CKD-EPI creatinine equation for estimating GFR expressed for specified race, sex, and serum creatinine in mg/dL (conventional units)**

Race | Sex | Serum creatinine, SCr (mg/dL) | Equation (age in years for ≥ 18) |
---|---|---|---|

Black | female | ≤ 0.7 | GFR = 166 × (SCr/0.7)^{-0.329} × (0.993)^{Age} |

Black | female | > 0.7 | GFR = 166 × (SCr/0.7)^{-1.209} × (0.993)^{Age} |

Black | male | ≤ 0.9 | GFR = 163 × (SCr/0.9)^{-0.411} × (0.993)^{Age} |

Black | male | > 0.9 | GFR = 163 × (SCr/0.9)^{-1.209} × (0.993)^{Age} |

White or other | female | ≤ 0.7 | GFR = 144 × (SCr/0.7)^{-0.329} × (0.993)^{Age} |

White or other | female | > 0.7 | GFR = 144 × (SCr/0.7)^{-1.209} × (0.993)^{Age} |

White or other | male | ≤ 0.9 | GFR = 141 × (SCr/0.9)^{-0.411} × (0.993)^{Age} |

White or other | male | > 0.9 | GFR = 141 × (SCr/0.9)^{-1.209} × (0.993)^{Age} |

#### SI Units

The equation can be expressed as a single equation in SI units:

**eGFR = 141 × min(SCr/κ, 1) ^{α} × max(SCr/κ, 1)^{-1.209} × 0.993^{Age} × 1.018 [if female] × 1.159 [if African American]**

Abbreviations/units

- eGFR = estimated GFR in mL/min/1.73 m
^{2} - SCr = standardized serum creatinine in µmol/L
- κ = 61.9 (females) or 79.6 (males)
- α = -0.329 (females) or -0.411 (males)
- min = indicates the minimum of SCr/κ or 1
- max = indicates the maximum of SCr/κ or 1
- age = years

Alternately, the equation can be expressed as a series of equations for different race, sex, and creatinine conditions, as shown in Table 2.

**Table 2. 2009 CKD-EPI creatinine equation for estimating GFR expressed for specified race, sex, and serum creatinine in µmol/L (SI units)**

Race | Sex | Serum Creatinine, SCr (µmol/L) | Equation (age in years for ≥ 18) |
---|---|---|---|

Black | female | ≤ 61.9 | GFR = 166 × (SCr/61.9)^{-0.329} × (0.993)^{Age} |

Black | female | > 61.9 | GFR = 166 × (SCr/61.9)^{-1.209} × (0.993)^{Age} |

Black | male | ≤ 79.6 | GFR = 163 × (SCr/79.6)^{-0.411} × (0.993)^{Age} |

Black | male | > 79.6 | GFR = 163 × (SCr/79.6)^{-1.209} × (0.993)^{Age} |

White or other | female | ≤ 61.9 | GFR = 144 × (SCr/61.9)^{-0.329} × (0.993)^{Age} |

White or other | female | > 61.9 | GFR = 144 × (SCr/61.9)^{-1.209} × (0.993)^{Age} |

White or other | male | ≤ 79.6 | GFR = 141 × (SCr/79.6)^{-0.411} × (0.993)^{Age} |

White or other | male | > 79.6 | GFR = 141 × (SCr/79.6)^{-1.209} × (0.993)^{Age} |

### MDRD Study Equation

The MDRD Study equation estimates GFR using age, sex, race, and serum creatinine.^{2} The equation can be calculated in conventional or SI units.

#### Conventional Units

**eGFR = 175 × (SCr) ^{–1.154} × (Age)^{–0.203} × (0.742 if female) × (1.212 if African American)**

Abbreviations/units

- eGFR = estimated GFR in mL/min/1.73 m
^{2} - SCr = standardized serum creatinine in mg/dL
- age = years

#### SI Units

**eGFR = 175 × (SCr/88.4) ^{–1.154} × (Age)^{–0.203} × (0.742 if female) × (1.212 if African American)**

Abbreviations/units

- eGFR = estimated GFR in mL/min/1.73 m
^{2} - SCr = standardized serum creatinine in µmol/L
- age = years