Table 2.

Residual Kidney Function Study Equations for Estimating CL_UREA or CL_{UREA, CREAT}

CLUREA, mL/min
Urea, Creatinine	CLUREA (mL/min) = 1.1 × UN0.949 × Creatinine−1.544
BTP	CLUREA (mL/min) = 69 × BTP−2.114 × 1.677 if male
B2M	CLUREA (mL/min) = 1711 × B2M−2.328 × 1.610 if male
Cystatin C	CLUREA (mL/min) = 64 × Cystatin C−2.211
BTP, B2M	CLUREA (mL/min) = 385 × BTP−1 450 × B2M−0.965 × 1.694 if male
CLUREA, CREAT, mL/min/1.73 m2
Urea, Creatinine	CLUREA, CREAT (mL/min/1.73 m2) = 2.4 × UN0.984 × Creatinine−1.868
BTP	CLUREA, CREAT (mL/min/1.73 m2) = 95 × BTP−2.16 × 1.652 if male
B2M	CLUREA, CREAT (mL/min/1.73 m2) = 2852 × B2M−2.417 × 1.592 if male
Cystatin C	CLUREA, CREAT (mL/min/1.73 m2) = 123 × Cystatin C−2.468
BTP, B2M	CLUREA, CREAT (mL/min/1.73 m2) = 673 × BTP−1 406 × B2M−1.096 × 1.670 if male

Abbreviations: CL_UREA, urinary urea clearance (mL/min); CL_{UREA, CREAT,} average of urinary urea and creatinine clearance (mL/min/1.73 m²); UN, serum urea nitrogen; BTP, β-trace protein; B2M, β2 microglobulin

Note: Coefficients for urea nitrogen and creatinine are expressed for concentrations in mg/dL. Conversion factors for units: creatinine in mg/dL to μmol/L, X 88.4; urea nitrogen in mg/dL to mmol/L, X 0.357.