51Cr-EDTA clearance determined by one plasma sample.

51Cr-EDTA clearance was measured in 99 consecutive patients. Based on the individual plasma activity at 180, 200, 220, and 240 min after injection (normalized with respect to injected dose/body surface area), a nomogram and a formula were derived for the relation between clearance and the plasma activity in one sample drawn between 180 and 240 min after injection. The nomogram was tested by the activity in 141 plasma nomogram were compared to the corresponding clearance value calculated by a conventional standard method. The correlation coefficient for this comparison was r = 0.982. It is recommended that the nomogram should only be used if clearance values above 30 ml/min are expected.