Falsely elevated serum digitoxin concentrations due to cross-reactivity ofwater-extractable digitoxin-like immunoreactivity of Chinese medicine ChanSU: elimination of interference by use of a chemiluminescent assay
Da. Biddle et al., Falsely elevated serum digitoxin concentrations due to cross-reactivity ofwater-extractable digitoxin-like immunoreactivity of Chinese medicine ChanSU: elimination of interference by use of a chemiluminescent assay, CLIN CHIM A, 300(1-2), 2000, pp. 151-158
Chinese medicines are available without prescription in health food stores.
One such Chinese preparation, Chan SU, is used as a cardiotonic agent. Dig
oxin-like immunoreactivity of Chan SU has been reported in the past. in thi
s report we demonstrated significant digitoxin-like immunoreactivity of Cha
n SU. For example, when a 20-mu l aliquot of an aqueous extract of Chan SU
(2 mg/ml) was added to drug-free serum, the observed digitoxin-like immunor
eactivity was 51.40 ng/ml by the fluorescence polarization assay. In contra
st, a new chemiluminescent assay for digitoxin did not show any immunoreact
ivity. When very small amount of aqueous extract of Chan SU was added into
serum containing digitoxin, the observed digitoxin concentrations were fals
ely elevated when measured by the fluorescence polarization immunoassay (FP
IA) but did not change significantly when measured by the chemiluminescent
immunoassay (CLIA), Significant digitoxin-like immunoreactivity was also ob
served (FPIA) in mice after feeding with Chan SU. Because bufalin, cinobufo
talin and cinobufugin are major components of Chan SU, digitoxin-like immun
oreactivity of these purified compounds was also studied. Bufalin was ident
ified as the major digitoxin-like immunoreactive compound responsible for m
ost of the interference in serum digitoxin measurement using the FPIA. (C)
2000 Elsevier Science B.V. All rights reserved.