ABSTRACT
Therapeutic monitoring of digitalis compounds has been challenging, despite improvements made in immunochemistry assays over the past several decades. Commercial immunoassays that have been introduced have been plagued with bias and interference caused by exogenous and endogenous substances. Resolving individual cases has lead to the development of a method composed of an initial separation of immunoreactive components by high performance liquid chromatography (HPLC), the collection of eluted fractions, and the measurement of immunoreactive components by immunoassay. We refer to this approach as HPLC-immunoassay (HPLC-IA) technique-a reference method that effectively identifies the desired compound as well as interfering substance(s). This reference method also provides a means of generating purified compounds to confirm observed interference or
discrepancy between immunoassay results and better characterize the immunochemistry detection. This chapter will outline the challenges in clinical monitoring of digoxin, describe the HPLC-IA and present several examples in which this approach was used to resolve discrepant immunoassay results.
