Serum copeptin level predicts a rapid decrease of overhydration after kidney transplantation.

Background: The assessment of proper hydration status in hemodialysis patients is difficult. None of currently available markers or measures is clinically relevant. Recently, human pre-pro-vasopressin (1-164) split product [copeptin (CPP)] - a new surrogate marker of hydration status - was introduced. The aim of the study was to analyze body weight changes in the early post-transplant period in relation to serum CPP levels before kidney transplantation.

Methods: Serum CPP and NT-proBNP concentrations and osmolality were measured in 130 kidney recipients directly prior to transplantation and, additionally, in 78 of them at 14th day post-transplant. Hydration status at transplantation was calculated from the difference in the patient's body weight before transplantation and at the discharge.

Results: During the post-transplant hospitalization, the average weight change was -1.6 kg, varying from 10.5 kg loss to weight gain of 5 kg. The overall weight loss was significantly related to pretransplant serum concentration of CPP (r=0.238), but not of NT-proBNP or osmolality. Patients with the lowest initial CPP level (first tertile) had smaller post-transplant weight loss. The early kidney graft function was unrelated to pretransplant CPP. Multivariate regression model revealed that variability of post-transplant weight loss is explained by the number of antihypertensive drugs used prior to transplantation [β=0.213 (0.049-0.377)] and pretransplant CPP values [β=0.233 (0.069-0.397)].

Conclusions: Elevated serum CPP level predicts a rapid weight loss after kidney transplantation and seems to characterize the subgroup of patients with the greatest overhydration. These results suggest the dysregulation of physiological mechanisms of CPP secretion in hemodialysis patients.