Why use it

Standard method for estimating GFR and staging CKD. Required for drug dosing adjustments. Recommended by KDIGO 2024 guidelines. The 2021 race-free equation is now the preferred standard.

About

The 2021 CKD-EPI creatinine equation estimates glomerular filtration rate (eGFR) from serum creatinine, age, and sex. This updated equation removed the race coefficient following recommendations by the NKF-ASN Task Force, providing a single equation for all races. It is more accurate than the older MDRD equation, especially at higher GFR values.

When to use

Screening and staging of chronic kidney disease
Drug dose adjustments for renally cleared medications
Monitoring renal function over time
Pre-operative renal assessment

Formula

eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(-1.200) × 0.9938^Age × (1.012 if female) κ = 0.7 (female), 0.9 (male) α = -0.241 (female), -0.302 (male) Scr = serum creatinine (mg/dL)

Pearls & pitfalls

The 2021 CKD-EPI equation does NOT use race — applicable to all populations.
Creatinine-based eGFR is inaccurate in extremes of muscle mass (bodybuilders, amputees, cachexia).
Cystatin C-based eGFR can be used for confirmation when creatinine is unreliable.
eGFR should be combined with albuminuria (UACR) for complete CKD staging.
Acute kidney injury: eGFR is unreliable — use urine output and creatinine trends instead.
Serum creatinine must be in steady state for eGFR to be valid.

Next steps

eGFR ≥ 90: Normal (Stage 1 if albuminuria present). 60-89: Mildly decreased (Stage 2). 45-59: Stage 3a. 30-44: Stage 3b. 15-29: Stage 4, nephrology referral. < 15: Stage 5, prepare for RRT.

Evidence

The 2021 CKD-EPI equation (Inker et al., NEJM 2021) was developed from 23,652 participants across 25 studies. Endorsed by KDIGO, NKF, ASN. Performs better than MDRD at eGFR > 60.

References

Inker LA et al. New Creatinine- and Cystatin C-Based Equations to Estimate GFR without Race. N Engl J Med. 2021;385(19):1737-1749. — link

CKD-EPI (eGFR)

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