Validity testing of the accu pinch tm thc test

Self-contained drug-testing kits are currently being marketed for a variety of drugs of abuse. These tests are designed to provide rapid access to test results without the need for laboratory facilities. This report describes a validity study of the accu PINCH TM THC test, a self-contained test for cannabinoids in urine. Three healthy male volunteers with a history of marijuana use participated in the clinical study. Each subject smoked one, two, or four marijuana cigarettes (2.6% THC) on each test day. Urine samples were collected and incorporated into a specimen set consisting of 178 clinical samples, 72 urine samples containing known amounts of drug, and 50 drug-free urine samples. The specimen set was randomized and analyzed under blind conditions by the accuPINCH test and by gas chromatography-mass spectrometry (GC-MS) for 11-nor-9-carboxy-Δ⁹-tetrahydrocannabinol (THCCOOH). AccuPINCH results were interpreted independently by three readers as positive at either two calibration points (positive A < 100 ng/mL THCCOOH; positive B ≥ 100 ng/mL THCCOOH) or negative. Concordance analysis was performed by comparison of the accuPINCH results with GC-MS. In addition, the effects of changes in sample turbidity, temperature, and assay reading time on test outcome were assessed. For the clinical samples, positive B results were associated exclusively with THCCOOH concentrations greater than or equal to 15 ng/mL, whereas positive A and negative results were obtained at all concentrations. All drug-free urine samples were interpreted as either negative or positive A. The test demonstrated relatively low cross-reactivity with THC and other cannabinoids. AccuPINCH was highly sensitive to sample turbidity but relatively insensitive to changes in sample temperature. Reading times longer than the recommended 5 min resulted in an increase in positive results. Overall, the accuPINCH test was easy to perform and generally produced valid positive B readings. However, positive A and negative readings were not always confirmed by GC-MS.