Evaluation of the CEDIA DAU assays and the AxSym system for the analysis of cannabinoids in whole blood.

The Microgenics CEDIA DAU (EIA) and the Abbott AxSym system (FPIA) cannabinoids assays were evaluated for their combined effectiveness in the analysis of cannabinoids in whole blood. Blood samples were treated with acetone, evaporated, and reconstituted, and the supernatant was analyzed by the EIA cannabinoids assay. Blood samples determined positive by EIA were then treated with acetonitrile and sodium sulfate, and the resultant protein-free supernatant was analyzed using the FPIA cannabinoids assay. A total of 98 blood samples determined to be presumptively positive by both EIA and FPIA were further analyzed for the presence of 11-nor-carboxy-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH). All 98 blood samples could be confirmed for the presence of THCCOOH by gas chromatography-mass spectrometry (GC-MS) at concentrations greater than the 10 ng/mL cutoff. The GC-MS results were found to correlate significantly better with those of the FPIA cannabinoids assay (r = 0.75) than with EIA (r = 0.22). Procedures for the rapid analysis of whole blood for cannabinoids using CEDIA DAU reagents and the AxSym system are presented.