Determination of ⁵¹Cr-EDTA Clearance Between 15 and 40 Ml/Min/1.73 M² by a Single Plasma Sample

Abstract

A single-sample method for calculation of ⁵¹Cr-EDTA clearance (Cl) between 15 and 40 ml/min/1.73 m² (C1_B) is introduced. It was tested in 109 consecutive patients and compared with a previously published single-sample method for calculation of Cl for C1≥30 ml/min/1.73 m² (C1_A). When Cl≥40 ml/min/1.73 m² the results were more precise when calculated as C1_B than when calculated as C1_A (p≥0.05). The C1_A values were more precise than the C1_B values when Cl was ≥40 ml/min/1.73 m² (p<0.01). Used in combination (Cl_A/B) there was a close correlation with Cl (r=0.98) for the whole range of tested clearance values. It is concluded that Cl can be precisely determined by combined use of the two methods, provided Cl>15 ml/min/1.73 m² and the single blood-sample is drawn between 240 and 300 min after the injection. If Cl_A/B>15 ml/min/1.73 m² it is recommended that a second blood-sample be drawn after 24 h and that C1 is calculated by a conventional slope method.

Key Words:

• ⁵¹Cr-EDTA clearance
• glomerular filtration rate
• renal function