Falsely elevated digoxin concentrations in patients with liver disease.

Immunoreactive digoxin was determined in blood samples of 73 patients with liver disease who did not take any cardiac glycoside. Seventeen of these patients reproducibly showed false-positive results, as much as 3.6 ng/ml. Patients with concomitant renal disease had higher assay results (mean 1.9 n/ml) than patients with normal renal function (mean 0.6 ng/ml). It is concluded that blood of a number of patients with liver disease of different causes contains a substance that interferes with digoxin radioimmunoassay.