Predicting glomerular function from adjusted serum creatinine in renal transplant patients.

In 22 individuals with a renal graft the correlations between the renal clearance of polyfructosan (CLPF), renal creatinine clearance (CLcr)--established under the same conditions as CLPF--and the value of glomerular function predicted using the equation by Cocroft and Gault (PredCLcr) were followed up, at an interval of 2-3 months, for 8-22 months. A significant linear correlation (r = 0.777, p < 0.001) was found between PredCLcr and CLPF as well as between PredCLcr and CLcr (r = 0.801, p < 0.001). Equally significant correlations, however, were established when relating the serum concentrations of creatinine (Scr) to 1/CLPF (r = 0.784, p < 0.001) and Scr to 1/CLcr (r = 0.744, p < 0.001). The values of the PredCLcr/CLPF and PredCLcr/CLcr ratios during follow-up in one and the same individual may vary significantly. This fluctuation exceeds maximal error of the analytical methods employed in one third of the individuals examined. When considering stabilization or slow changes in graft function on the basis of PredCLcr and CLPF we found significant discrepancies in more than one half of the individuals examined (64%). The findings support the assumption that more accurate methods must be used to assess graft glomerular function on long-term follow-up.