. Author manuscript; available in PMC: 2022 May 1.

Published in final edited form as: Am J Kidney Dis. 2020 Dec 7;77(5):673–683.e1. doi: 10.1053/j.ajkd.2020.11.005

Table 2 :

Variables and Coefficients in 2020 Equations in Development and Internal Validation Population

Sex	Serum Creatinine mg/dl	Serum Cystatin C mg/L	Serum BTP mg/L	Equation for Estimating GFR
2020 Cystatin C-B2M-BTP Equation
Female		≤0.8	≤0.6	110 × (Scys/0.8) ^−0.876 × B2M^−0.205 × (SBTP/0.6) ^0.038 × 0.999^age
			>0.6	110 × (Scys/0.8) ^−0.876 × B2M^−0.205 × (SBTP/0.6) ^−0.243 × 0.999^age
		>0.8	≤0.6	110 × (Scys/0.8) ^−0.697 × B2M^−0.205 × (SBTP/0.6) ^0.038 × 0.999^age
			>0.6	110 × (Scys/0.8) ^−0.697 × B2M^−0.205 × (SBTP/0.6) ^−0.243 × 0.999^age
Male		≤0.8	≤0.6	120 × (Scys/0.8) ^−0.876 × B2M^−0.205 × (SBTP/0.6) ^0.038 × 0.999^age
			>0.6	120 × (Scys/0.8) ^−0.876 × B2M^−0.205 × (SBTP/0.6) ^−0.243 × 0.999^age
		>0.8	≤0.6	120 × (Scys/0.8) ^−0.697 × B2M^−0.205 × (SBTP/0.6) ^0.038 × 0.999^age
			>0.6	120 × (Scys/0.8) ^−0.697 × B2M^−0.205 × (SBTP/0.6) ^−0.243 × 0.999^age
2020 Creatinine-Cystatin C-B2M-BTP Equation
Female	≤0.7	≤0.8	≤0.6	123 × (Scr/0.7) ^−0.243 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	123 × (Scr/0.7) ^−0.243 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.177 x0.996^age
		>0.8	≤0.6	123 × (Scr/0.7) ^−0.243 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	123 × (Scr/0.7) ^−0.243 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age
Female	>0.7	≤0.8	≤0.6	123 × (Scr/0.7) ^−0.471 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	123 × (Scr/0.7) ^−0.471 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age
		>0.8	≤0.6	123 × (Scr/0.7) ^−0.471 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	123 × (Scr/0.7) ^−0.471 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age
Male	≤0.9	≤0.8	≤0.6	131 × (Scr/0.9) ^−0.295 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	131 × (Scr/0.9) ^−0.295 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age
		>0.8	≤0.6	131 × (Scr/0.9) ^−0.295 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	131 × (Scr/0.9) ^−0.295 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age
Male	>0.9	≤0.8	≤0.6	131 × (Scr/0.9) ^−0.471 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	131 × (Scr/0.9) ^−0.471 × (Scys/0.8) ^−0.519 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age
		>0.8	≤0.6	131 × (Scr/0.9) ^−0.471 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.004 × 0.996^age
			>0.6	131 × (Scr/0.9) ^−0.471 × (Scys/0.8) ^−0.423 × B2M^−0.103 × (SBTP/0.6) ^−0.177 × 0.996^age

^**

2020 Cystatin C- B2M-BPT equation can be expressed as a single equation: 120 X min(Scys/0.8,1) ^−0.876 X max(Scys/0.8,1) ^−0.697 X B2M^−0.205 X min(SBTP/0.6,1) ^0.038 X max(SBTP/0.6,1) ^−0.243 X 0.999^age [X 0.922 if female], where Scys is serum cystatin C, B2M, Beta2-Microglobulin; BTP, Beta-Trace Protein

^***

2020 Creatinine-Cystatin C-B2M-BTP Equation can be expressed as a single equation 131 X min(Scr/k,1)^α X max(Scr/k,1) ^−0.471 X min(Scys/0.8,1) ^−0.519 X max(Scys/0.8,1) ^−0.423 X B2M^−0.103 X min(SBTP/0.6,1) ^−0.004 X max(SBTP/0.6,1) ^−0.177 X 0.996^age [X 0.937 if female] where Scr is serum creatinine Scys is serum cystatin C, SB2M is serum B2M, SBTP is serum BTP; B2M, Beta 2-Microglobulin; BTP, Beta-Trace Protein, k is 0.7 for females and 0.9 males, α is -0.243for females and -0.295for males, min indicates the minimum of Scr/k or 1, max indicates the maximum of Scr/k or 1

All equations were developed by the CKD-EPI research group.