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College

Seattle University

Major

Eabha-chemistry Jennifer-Chemistry & Criminal Justice

Faculty Mentor

Kristen Skogerboe

Abstract

Drug testing, a crucial tool in clinical, occupational, parental, and forensic settings, aims to detect and deter illicit substance use. The accuracy of a urine drug test is determined by both sensitivity, the ability to correctly identify true positives, and specificity, the ability to correctly identify true negatives. This study assesses the accuracy of five different lateral flow immunoassay (LFI) testing devices for marijuana usage on 22 anonymous urine samples (12 positives and 10 negatives) as performed by students in Seattle University’s forensic science laboratory. Students on site interpreted the results of their tests, and photographs of the tests were interpreted by four blind participants. Overall, 10 of the 22 samples had a false result with at least one of the LFI tests. Of the five test devices that were investigated, only one demonstrated 100% accuracy with sensitivity and specificity. The other four devices had sensitivities ranging from 45 to 100% and specificities ranging from 80 to 100%. These findings underscore the considerable variability in sensitivity and specificity, factors that are contingent on the test kit itself and the person interpreting the test results. Four different types of errors were identified to account for these inaccurate results: 1) false invalid interpretation, 2) switching the sign of a positive and negative result, 3) difficulty in visual confirmation of the presence of a test line, and 4) sample matrix variability, which occurs when constituents in the sample, other than the substance being measured, impact the result. The primary consumers of drug tests—healthcare workers, employers, parents, law enforcement agencies, and forensic experts—have tremendous influence on our society; the results of this study generate a valuable, challenging discussion about the need for standardized interpretation and enhanced accuracy within the drug testing industry.

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