Efficacy of screening tests for 11-nor-delta-9-tetrahydrocannabinol -carboxylic acid detection in urine

Abstract

Context: Cannabis-abused drivers in Thailand were lower prevalence than alcoholic and amphetamine addicts and police officers were often disregarded. Thus, determination of cannabis metabolites by Thai screening test kits was most important driver inspection. However, missing of interpretation on results of cannabis screening test kits were commonly happening, which according by different of immunoassay application and/or procedure. Urine storage condition was affected to screening results and also may affect to results of confirmatory test by gas chromatography/mass spectrometry (GC/MS). Aims: To compare efficacy of test kits for 11-nor-delta-9-tetrahydrocannabinol-carboxylic acid (THC-COOH) detection in urine and studied on urine storage condition effects on THC-COOH detection using different test kits and GC/MS for screening and confirmatory method, respectively. Materials and Methods: Each standard THC-COOH solution was dissolved in pooled-urine (10–200 ng/ml), which was applied to three commercial test kits. The calculation of sensitivity, specificity, positive predictive value, negative predictive value, and efficiency of test was done. Each pooled-urine containing with THC-COOH (50 ng/ml) was stored in different temperatures and duration prior analysis by test kits and GC/MS. Results and Discussion: Three commercial test kits were gave positive results at 50–200 ng/ml of THC-COOH. No false positive result was appeared. THC-COOH in pooled-urine was detected at 25, 4, and −20°C during 1, 7, and 14 days for all test kits. THC-COOH in storage urine at room temperature (25°C) and longest period (14 days) was able to detect by GC-MS, however, in low concentration. Conclusions: Research finding was providing useful information for forensic laboratory where perform THC-COOH detection for both screening and confirmatory tests