Reference data for 51Cr-EDTA measurements of the glomerular filtration rate derived from live kidney donors

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Abstract
51Cr-Ethylenediaminetetraacetic acid (51Cr-EDTA) is widely used to measure the glomerular filtration rate (GFR) for the assessment of renal function. The aims of this study were to assess the dependence of GFR on age and gender and to produce reference data for the interpretation of 51Cr-EDTA GFR measurements in adults. This was a retrospective study of 428 subjects (218 females, 210 males; age range, 19–72 years) undergoing assessment as live kidney donors. GFR was evaluated from 51Cr-EDTA plasma clearance using blood samples taken at 2, 3 and 4 h. The slope–intercept GFR was corrected for body surface area using the Haycock formula and for the fast exponential using the Brochner–Mortensen equation. The data were analysed for the dependence on age and gender using multivariate regression analysis. Precision was evaluated from duplicate measurements in 22 subjects. For 187 subjects, aged 19–40 years, the dependence of GFR on age was not statistically significant (P=0.51). The mean GFR was 103.4 ml·min−1·(1.73 m2)−1 with a root mean standard error (RMSE) of 15.5 ml·min−1·(1.73 m2)−1. GFR was 1.3 ml·min−1·(1.73 m2)−1 higher in men than in women, although the difference was not significant (P=0.56). In 241 subjects, aged 40–73 years, GFR decreased by 0.91 ml·min−1·(1.73 m2)−1 per year [standard error, 0.06 ml·min−1·(1.73 m2)−1 per year] with an RMSE of 13.6 ml·min−1·(1.73 m2)−1. Over both age groups GFR was 0.4 ml·min−1·(1.73 m2)−1 higher in men than in women [P=0.80; 95% confidence interval, −2.4 to +3.1 ml·min−1·(1.73 m2)−1]. For the 22 subjects with duplicate measurements, the root mean square coefficient of variation was 10.4%. A model for the decline of GFR with age was produced in which GFR remains constant at 103.4 ml·min−1·(1.73 m2)−1 until the age of 40 years and then declines at a rate of 9.1 ml·min−1·(1.73 m2)−1 per decade. The data can be used to report the results of adult 51Cr-EDTA GFR investigations.