. Author manuscript; available in PMC: 2022 May 4.

Published in final edited form as: N Engl J Med. 2021 Sep 23;385(19):1750–1760. doi: 10.1056/NEJMoa2103753

Table 4.

Comparison of Model Performance and Race Coefficients from GFR Estimating Equations Based on Cystatin C.^*

Model Covariates	Median Difference between iGFR and eGFR (95% CI)		P₃₀ (95% CI)		P₁₀ (95% CI)		Percent Higher iGFR for Black Race or 10% Increase in Percentage of African Ancestry (95% CI)
	Black	Non-Black	Black	Non-Black	Black	Non-Black
	ml/min/1.73 m²
Cystatin C, age, and sex	0.33 (−1.43 to 1.92)	0.29 (−0.84 to 1.36)	85 (79 to 90)	83 (78 to 87)	41 (34 to 49)	39 (33 to 45)	—
Cystatin C, age, sex, and race as reported by the participants	0.85 (−1.05 to 2.51)	0.03 (−1.00 to 1.12)	85 (79 to 90)	83 (78 to 87)	42 (35 to 50)	39 (33 to 45)	−1.6 (−4.7 to 1.4)^†
Cystatin C, age, sex, and percentage of African ancestry	0.90 (−1.14 to 2.34)	0.04 (−0.95 to 1.14)	85 (79 to 90)	83 (78 to 87)	42 (35 to 50)	39 (33 to 45)	−0.2 (−0.6 to 0.2)^†

Coefficients for race as reported by the participants and genetic ancestry are not significant in GFR estimating equations that rely on cystatin C; those equations perform similarly to GFR estimating equations that rely on serum creatinine. Models were derived from a development subgroup of 844 participants (68%), and performance of estimated GFR was reported in a validation set of 404 participants (32%). All 95% confidence intervals correspond to the 2.5th and 97.5th percentile values from 1000 bootstrapped samples of the validation set.

^†

The percentage difference was obtained by exponentiating the coefficient for Black race or the percentage of African ancestry in models derived in the development data set (844 participants).