'Digoxin-like' substance in serum of elderly patients.

The Amersham Amerlex Radio-immunoassay was used to detect 'digoxin-like' substance in the sera of 37 elderly subjects, nine with renal impairment, 14 with hepatobiliary disease and 14 over-65-years-old controls with no renal or hepatic impairment. In the patients with hepatobiliary disease, digoxin-like substance was detected in 11 out of 14, the level being closely correlated with serum bilirubin (P less than 5.5 X 10(-10)) and significantly but less closely with serum alkaline phosphatase activity (P less than 10(-3)). While serum digoxin-like substance was detectable in seven out of nine patients with renal impairment, there was no correlation between the degree of renal impairment as reflected by blood urea and serum creatinine and serum digoxin-like activity. We suggest that in elderly subjects with renal impairment or hepatobiliary disease these findings should be borne in mind especially when considering digoxin toxicity.