Evaluation of the Rapidrog Cannabis Noninstrumental Immunoassay

Procedures designed to detect cannabis use by analyzing urine samples for the presence of 11-nor-Ag-tetrahydrocannabino!-9-carboxylic acid (THCCOOH) are well-documented. The traditional approach is to screen urine by immunoassay and submit the presumptive positive samples for by gas chromatography-mass spectrometry (GC-MS). Several commercial instrumental and noninstrumental immunoassays are available on the market. Recently, new regulations in Europe concerning driving under the influence of drugs have increased manufacturers' interest in proposing simple and single noninstrumental immunoassays. To document the usefulness of the RapiTest THC (Princeton Biomeditech Corporation, Princeton, N J), which is marketed in France under the trade name Rapidrog Cannabis (J2L Diffusion, Labarthe Inard, France), 92 urine samples obtained from a detoxification center were simultaneously tested by this immunoassay, fluorescence polarization immunoassay (FPIA), and GC-MS. The Rapidrog Cannabis test is based on the principle of detecting drugs by an immunochromatographic reaction, or CICA (colored immuno chromatography assay). The urine sample flows through a membrane by capillary action. The dye conjugate complex on the test membrane and the drug present in the urine compete for the antibody present on the test membrane. In the absence of the drug, the antibody is free to react with the dye conjugate, and a colored band appears in the test window. A control band is included with the test to confirm validity. The positive cutoff value is fixed at 50 ng/mL of THCCOOH (1). The result is obtained 3 min after pipetting five drops of urine into the test sample cavity. If the test is positive, only one band will appear; if the test is negative, two bands will appear. FPIA and GC-MS analyses were achieved according a Table I. Method Comparison for Rapidrog, FPIA, and previous paper (2) with 25 and 15 ng/mL of THCCOOH GC-MS as positive cutoffs, respectively. Method Number of positives Number of negatives Results are presented in Table I. When using the GC-MS cutoff of 15 ng/mL, 54 of the 92 samples were GC-MS 54