Time course of low molecular weight proteins in the early kidney transplantation period--influence of corticosteroids.

Background: Cystatin C (Cys C) is an established new marker of renal function in patients with various renal diseases and in kidney transplantation. However, few data are available for the early post-transplantation period.

Methods: Twenty-two patients who underwent renal transplantation (RTx) were evaluated for the kinetics of Cys C from day 0 to 14 in relation to creatinine and beta-2 microglobulin (B2MG). Blood samples were obtained immediately before and after transplantation and on a daily basis thereafter. Serum levels before transplantation (100%) were used to calculate reduction ratios.

Results: The decrease of the analytes differed considerably: immediately after RTx Cys C declined by 27.3% (P < 0.01). However, after 3 days, on average, all patients showed a significant increase in Cys C levels (15+/-2.5%; P < 0.01). B2MG levels fell quickly by 55.4 and 73.8% after days 1 and 7, respectively, and remained stable thereafter. In contrast, creatinine did not decrease immediately after RTx but fell slowly by 67.5% at the end of the study. Prior to rejection, all analytes showed a similar behaviour. Rejection treatment with high-dose methylprednisolone induced a significant increase in Cys C (+22.8+/-7.9%, P < 0.05), while in parallel, creatinine and B2MG decreased (-12.9+/-3.4 and -8.4+/-6.89%).

Conclusions: Corticosteroid treatment for induction of immunosuppression or rejection therapy significantly induces Cys C, but decreases B2MG. Cys C and B2MG are not helpful in establishing the diagnosis of rejection earlier. Thus, our data indicate that Cys C and B2MG testing does not accurately reflect changes in the glomerular filtration rate early after transplantation.