Calculators · Nephrology · Formula

eGFR — CKD-EPI creatinine–cystatin C (2021) and cystatin C (2012)

Also called eGFRcr-cys, eGFRcys, cystatin C eGFR

Confirmatory eGFR using cystatin C, alone or combined with creatinine; neither equation uses race.

mg/L
years
Sex

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Formula and scoring

cr-cys 2021: 135 × min(Scr/κ,1)^α × max(Scr/κ,1)^−0.544 × min(Scys/0.8,1)^−0.323 × max(Scys/0.8,1)^−0.778 × 0.9961^age × 0.963 [F]; κ 0.7/0.9, α −0.219 (F)/−0.144 (M). cys 2012: 133 × min(Scys/0.8,1)^−0.499 × max(Scys/0.8,1)^−1.328 × 0.996^age × 0.932 [F].

Exam and ward pearls

  • The combined equation is the confirmatory test: it reclassified 16.9% of people with eGFRcr 45–59 as having GFR ≥ 60 (Inker 2012).
  • Combined equations shrink the difference between race groups seen with creatinine alone.

When not to rely on it

  • Requires a cystatin C assay traceable to the international reference material.
  • Validated in ambulatory adults; not for acute illness.

Source

  1. Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737-1749. doi:10.1056/NEJMoa2102953 · PMID 34554658
  2. Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012;367(1):20-9. doi:10.1056/NEJMoa1114248 · PMID 22762315
  3. National Kidney Foundation. CKD-EPI creatinine-cystatin C equation (2021). Link
  4. National Kidney Foundation. CKD-EPI cystatin C equation (2012). Link

Formula and cut-offs checked against these sources on 8 Nov 2026. Educational tool for clinicians; it does not replace clinical judgement.

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