Volume 38, Issue 6 (November 1993)
Method Comparison of EMIT II and OnLine with RIA for Drug Screening
The newest formulation of the EMIT assay for drugs of abuse, EMIT II, and a new immunoassay, OnLine, using the kinetic interaction of microparticles in solution methodology, were evaluated for marijuana, cocaine, opiates, barbiturates, and phencyclidine. Both types of immunoassays were performed on an Hitachi 717 analyzer. Calibration curves, the degree of separation between negative and cutoff calibrators, precision, probability of carryover from positive to negative samples, and overall ease and speed of analysis were evaluated. EMIT II and OnLine were compared with RIA tests for the five drugs to determine each assay's ability to detect samples which confirm positive by GC/MS. The RIA and OnLine marijuana tests detected >99% of confirmed positive samples while EMIT II detected about 90%. All three immunoassays performed equivalently for cocaine and opiates, each assay detecting at least 98% of positives. Barbiturates showed the greatest disparity with OnLine detecting 96%, EMIT II 85%, and RIA 79% of confirmed positive samples. Too few phencyclidine positive samples were detected for a method comparison study. The fully automated EMIT II and OnLine assays are preferable for a variety of reasons to our laboratory's current semi-automated RIA tests for large volume urine testing. The immunoassays offer comparable performance for some drugs but not for others.