Endogenous digitalis-like immunoreactive substances in cord serum characterized by anti-digitoxin and anti-digoxin antibodies. Effect of modulated incubation conditions

Abstract

Digoxin-like immunoreactive substances (DLIS) have been extensively described in biological fluids of pregnant women, neonates and renal impaired patients, by the use of several digoxin immunoassays. In this paper a similar interference with anti-digitoxin antibodies is reported by investigating 20 cord sera. By increasing both the time and the temperature of the incubation, the levels of digitalis-like immunoreactive substances may be modulated and decreased to zero. Digitoxin- and digoxin-like immunoreactive substances have been successfully extracted with methanol and concentrated from cord serum. Our data suggest the competitive nature of DTLIS and DLIS interactions with digitalis antibodies. They also show a means of minimizing these interferences in routine digitalis immunoassays.