Detectability of Phencyclidine and 11-nor-Δ9-Tetrahydrocannabinol-9-Carboxylic Acid in Adulterated Urine by Radioimmunoassay and Fluorescence Polarization Immunoassay

The ability to alter immunoassay test results by the addition of some commonly available chemicals to drug-positive and drug-negative urine specimens was investigated. Urine specimens containing either phencyclidine (PCP) of Δ9-tetrahydrocannabinol-9-carboxylic acid (9-THC-COOH) were adulterated with sodium chloride, bleach, vinegar, potassium hydroxide, liquid soap, 2-propanol, and ammonia. Subsequent analyses by radioimmunoassay (RIA) and fluorescence polarization immunoassay (FPIA) demonstrated false positive and false negative results with some adulterants. Radioimmunoassay false positives occurred with potassium hydroxide (PCP and THC-COOH assays) and bleach (THC-COOH assay) adulterants. Bleach (PCP assay) and soap (THC-COOH assay) additives resulted in false negative analyses by RIA. No adulterant caused FPIA false positives. FPIA false negatives occurred with bleach (PCP and THC-COOH assays) and potassium hydroxide (PCP assay) adulterants.