Digoxin-like immunoreactive substance in renal transplant patients.

Digoxin-like immunoreactive substance (DLIS) has been detected in several patient populations that were not receiving digoxin, including those patients with end-stage renal disease. The structure and physiologic significance of this compound are unknown, and the fate of DLIS after renal transplantation has not been studied. The authors prospectively evaluated 163 patients (not receiving digoxin) before and after transplantation for the presence of DLIS. Three different assays were used: radioimmunoassay (RIA), affinity mediated immunoassay (ACA), and fluorescence polarization immunoassay (TDX I). Depending on the assay method used, 11% (RIA), 6% (ACA), and 9% (TDX) of patients had detectable DLIS pretransplant. Using all 3 assays, a total of 34 patients (21%) were found to have DLIS. The mean serum digoxin concentration was 0.41 +/- 0.13 ng/mL (range: 0.2-1.2 ng/mL) and DLIS was detectable by greater than 1 assay method in seven patients. DLIS persisted longer in patients who had delayed allograft function (13.7 +/- 7 days) than in those who did not (3 +/- 1.9 days), P less than .05. In summary, detection of DLIS in renal transplant recipients appears to be an infrequent occurrence when using a single digoxin assay method. When detected, the concentration of DLIS is often below the usual therapeutic range for digoxin and disappears once allograft function is established. The authors conclude that the presence of DLIS is unlikely to be clinically significant in the renal transplant population.