[Digoxin-like immunoreactivity in newborn infants--a pitfall of digoxin therapy?]

Endogenous digoxin-like immunoreactive substances (DLIS) show crossreactions with different immunoassays used for digoxin drug monitoring. In 61 blood samples of 47 eutrophic healthy newborns with jaundice, digoxin serum concentrations were measured during examination of serum bilirubin using a digoxin polarisation immunoassay. Although there was no digoxin therapy in any case, we found positive serum digoxin immunoreactivity (> or = 0.2 ng/ml) in 86% of serum samples. The mean DLIS-concentration was 0.43 +/- 0.19 ng/ml with a maximum of 0.9 ng/ml. We found a significant indirect correlation (rs = -0.34; p = 0.05) between age and serum DLIS concentration. A case report demonstrates the possibility of DLIS interference on digoxin drug monitoring.