Modification of Emit assay reagents for improved sensitivity and cost effectiveness in the analysis of hemolyzed whole blood.

ABSTRACT

This report describes an improved method for the direct detection of a broad spectrum of drugs of abuse in hemolyzed whole blood by means of Syva Emit enzyme immunoassay. Improvements include a 1.5 to 10 fold increase in Emit assay sensitivity along with a 2 to 4 times increase in the normal number of assays per kit. This was accomplished by enzyme substrate and cofactor supplementation with a commercially available product (Raichem), assay reagent dilution, and extension of the absorbance measure time. The Emit drug abuse in urine (d.a.u.) assays used in this study included amphetamine, barbiturate, methadone, methaqualone, opiate, benzodiazepine metabolite, phencyclidine, and propoxyphene. The Emit serum assays used were the benzodiazepine and the tricyclic antidepressant assays. The within-run coefficients of variation ranged from 0.25 to 0.66%, and the between-run coefficients of variation ranged from 0.45 to 1.00%. The proposed method allows for the analysis of hemolyzed whole blood using both Emit d.a.u. and serum assays. It is sensitive and can detect therapeutic or subtherapeutic concentrations of drugs in all assays tested. The method is simple, rapid, and allows for the direct analysis of a methanolic extract of whole blood without lengthy sample concentration steps. The method allows for the detection of highly potent drugs and for long-term monitoring of drug metabolites and conjugates. This could be beneficial for therapeutic drug monitoring, assessing patient compliance, and detection of previous drug use.