Estimation of glomerular filtration rate by serum creatinine and serum beta 2-microglobulin

51Cr-EDTA clearance, serum beta 2-microglobulin and serum creatinine were measured simultaneously on 271 occasions in 114 patients. Serum beta 2-microglobulin was more sensitive than serum creatinine for detection of changes of glomerular filtration rate (GFR) and for detection of a moderately reduced GFR. However, serum beta 2-microglobulin also had severe limitations when used to estimate GFR. The serum levels of the protein varied considerably in patients with similar GFR, probably due to different rates of synthesis of beta 2-microglobulin.