Endogenous digoxin-immunoreactive substance measured in several patient populations.

We have reported the presence of endogenous digoxin-like immunoreactivity in the bloods of patients in renal failure, of newborn infants, and of third-trimester pregnant women. Similar reactivity has also been detected in amniotic fluids and in the urine and serum of normal healthy subjects. The substance(s) giving rise to this immunoactivity cross-react with the antibodies used in many commercially available immunoassays for digoxin. In this brief review I summarize the findings of our laboratory in detecting this activity in the bloods of several clinical populations where the accurate measurement of digoxin may be compromised. Present data suggests the substance or group of substances being detected by these immunoassays are not one or a combination of elevated steroids or polypeptides commonly observed in these same clinical conditions. Some preliminary information on the physical characterization of this activity is also presented.