Although our sample size was limited, it comprised the recommended
number of individuals for identification of differences between
methods, assuming 90% statistical power. One strength of our paper
was the use of a reference method for GFR measurement, therefore
enabling comparison of the performance of creatinine-based GFR estimation
equations to a reference method. Although the clearance of
51Cr-EDTA is about 5–10% less than that of inulin (possibly due to activity
bound by plasma proteins), and also if an allowance of about 10% is
made for the arteriovenous concentration difference (higher venous
concentration), a composite correction factor applied to the slope clearance
provides a reasonable estimate of the GFR [14,39]. This simplified
one-compartment approach of GFR measurement is, nevertheless, less
reliable than a two-compartment system (double slope analysis) [40].