Assessment of glomerular filtration rate in diabetic nephropathy using the plasma clearance of 51Cr-EDTA

• Published in: Scandinavian journal of clinical and laboratory investigation Vol. 58; no. 5; pp. 405 - 414
• Main Authors: Hansen, H. P., Rossing, P., Mathiesen, E. R., Hommel, E. E, Smidt, U. M., Parving, H.-H.
• Format: Journal Article
• Language: English
• Published: Oslo Informa UK Ltd 01-08-1998; Taylor & Francis; Scandinavian University Press
• Subjects: Biological and medical sciences; Chromium Radioisotopes; Cross-Sectional Studies; Diabetic Nephropathies - blood; Diabetic Nephropathies - physiopathology; Edetic Acid - blood; Edetic Acid - pharmacokinetics; Female; Glomerular Filtration Rate; Humans; Investigative techniques, diagnostic techniques (general aspects); Longitudinal Studies; Male; Medical sciences; Radionuclide investigations; Urinary system; Endocrinopathy; Kidney disease; Radionuclide study; Human; Biological fluid; Urinary system disease; Glomerular filtration; Renal function; Radiolabelling; Diabetes mellitus; Clearance; Blood plasma; Nephropathy; Microalbuminuria
• ISSN: 0036-5513; 1502-7686
• DOI: 10.1080/00365519850186382

Plasma clearance of 51Cr-EDTA is widely used to assess the glomerular filtration rate (GFR) in diabetic nephropathy. Originally, the ratio between the intravenously injected amount of tracer and the total area under the plasma concentration curve was used for the calculation of total 51Cr-EDTA plasma clearance (CT). Simplified methods, using the final mono-exponential part of the plasma curve, have been suggested, e.g. four samples, taken 180 to 240 min after injection (CIV), or using one sample taken at 240 min (CI). Our aim was to evaluate the agreement between measurements of GFR and rate of in GFR based upon these three methods. Bland & Altman plots were used to illustrate the range of agreement. We investigated 76 insulin-dependent diabetic (IDDM) patients with microalbuminuria or diabetic nephropathy. GFR was measured after a single intravenous injection of 3.7 MBq 51Cr-EDTA by determining the radioactivity in venous blood samples taken 5, 7, 10, 15, 30, 45, 60, 90, 120, 150, 180, 200, 220,and 240 min after the injection. Rate of decline in GFR was assessed using 12 (6?17) determinations of GFR over a period of time of 8 (4?10) years. Mean (SD) GFRT was 123 (21) ml·min-1 compared to GFRIV 123 (21) ml·min-1 (NS) and GFRI 115 (17) ml·min-1 (p<0.00001). The mean difference (95% limits of agreement) between GFRT and GFRIV was + 0.6 (?16.6 to + 17.7) ml·min-1, and between GFRT and GFRI + 8.0 (?6.0 to + 22.2) ml·min-1. The difference between GFRT and GFRI was significantly correlated with their mean value (r=0.56, p<0.00001), indicating increasing underestimation by GFRI with increasing GFR levels. The mean (SD) rate of decline in GFRT was 2.3 (3.9) ml·min-1·year-1, compared to a mean rate of decline in GFRIV of 2.4 (3.6) ml·min-1·year-1 (NS), and a mean rate of decline in GFRI of 2.2 (3.5) ml·min-1·year-1 (NS). The mean difference (95% limits of agreement) between rate of decline in GFRT and rate of decline in GFRIV was + 0.16 (?1.59 to + 1.91) ml·min-1·year-1, and between rate of decline in GFRT and rate of decline in GFRI ?0.01 (?1.64 to + 1.61) ml·min-1·year-1, respectively. In conclusion, our cross-sectional study revealed a close agreement between GFRT and GFRIV with acceptable limits of agreement (precision), while GFRI lacked accuracy. However, a close agreement between rate of decline in GFRT and rate of decline in GFRIV, and between rate of decline in GFRT and rate of decline in GFRI, with acceptable limits of agreement (precision), suggests that both simplified methods are applicable for long-term follow-up.