Prediction of Glomerular Filtration Rate by Serum Creatinine and β2-Microglobulin

Abstract
The reciprocal of serum creatinine concentration (1/Cr) is often used to predict glomerular filtration rate (GFR). Serum creatinine also varies with age, size, and muscle mass, and so it may inaccurately estimate GFR. The reciprocal of serum β2 -microglobulin (1/β2µ) has been proposed as an alternative estimator of GFR. This study compares 1/Cr and 1/β2µ as predictors of GFR as measured by 125I-iothalamate clearance (Ciot) and creatinine clearance (Ccr) in 29 subjects with a wide range of age, size and kidney function, and including 12 chronic hemodialysis patients. 1/β2µ was a better predictor of Ciot (r = 0.90) and Ccr (r = 0.87) than 1/Cr (r = 0.50 and 0.78) was. In fact, in the non-dialysis population, 1/β2µ predicted Ciot (r = 0.86) about as well as Ccr predicted Ciot (r = 0.87). β2µ was less dependent on body size than Cr and unlike Cr, was not influenced by dialysis and did increase as GFR decreased with age. β2µ can be useful as an alternative clinical estimate of GFR, particularly when Cr is considerably influenced by factors other than renal function.

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