Prediction of glomerular filtration rate from changes in serum creatinine

The glomerular filtration rate (GFR) was estimated from serum creatinine concentration in patients in whom the individual relation between GFR and serum creatinine had been previously determined. 51Cr-EDTA plasma clearance was used as reference method for GFR. The relation between 51Cr-EDTA clearance and estimated GFR was determined from 340 investigations in 197 adult patients with a variety of infectious and internal diseases. The imprecision of estimated GFR was 46% (1 CV) at 20 ml/min, 23% at 45 ml/min, 20% at 75 ml/min and 18% at 110 ml/min. This poor precision was probably due to the fact that many patients with acute infectious diseases, congestive heart failure, diabetes mellitus, etc., have an unstable renal function and therefore their creatinine distribution is not under steady state. This must always be considered when serum creatinine is used to estimate GFR.