Screening for human drugs of abuse by particle concentration fluorescence immunoassay (PCFIA)

We have evaluated a panel of Particle Concentration Fluorescence Immunoassay (PCFIA) tests for use in drugs of abuse screening in humans. The tests evaluated include assays for opiates, cocaine, tetrahydrocannabinol, amphetamines, barbiturates and phencyclidine. These tests are exceptionally sensitive and rapid, since PCFIA readers are highly automated. The I-50 values for the major drugs of abuse in each assay were determined. The cocaine assay was half-maximally inhibited by about 50 ng/ml benzoylecgonine and was much more sensitive to parent cocaine. The amphetamine assay was half-maximally inhibited by 10 ng/ml of d,1-amphetamine, the phencyclidine assay by 1 ng/ml of phencyclidine, the tetrahydrocannabinol assay by 350 pg/ml of 11-nor-delta-8-tetra-hydrocannabinol-9-carboxylic acid, the opiate assay by less than 1 ng/ml of morphine and the barbiturate assay by less than 1 ng/ml of secobarbital. The sensitivity of the assays was such that test urines were diluted ten fold prior to testing. No false positives were observed in a series of 50 control urines and very few false negative were observed. On cross-reactivity studies the specificity and sensitivity of our panel of PCFI tests compared favorably with that of the Abott TDx(R) system. In our hands the PCFIA system was more sensitive than the TD(R) and correlated better with the gas chromatograph/mass spectroscopy status of some of these samples. Beyond this, the potential for automation and sample throughput with the Baxter/Pandex Screen Machine and PCFIA technology is currently unmatched by any immunoassay technology.