Tentative identification of a digoxin-like immunoreactive substance.

: Three independent immunoassays gave significantly different results when digoxin concentrations were measured in plasma samples from a 68-year-old male patient with renal and liver impairment. These differences were used to provide a means of isolating a digoxin-like immunoreactive substance (DLIS) by high-pressure liquid chromatography. Examination of this fraction by fast atom bombardment-mass spectrometry provided data to support the hypothesis that excess bile acids might be the source of the DLIS in our patient which may also explain the DLIS observed in neonates.