Abstract
Immunochromatographic strips for urine drug screening tests (UDSTs) are common and very suitable for drug abuse monitoring, but are also highly susceptible to adulterants kept in the household, which can significantly alter test results. The aim of this study was to see how some of these common adulterants affect UDST results in practice and whether they can be detected by sample validity tests with pH and URIT 11G test strips. To this end we added household chemicals (acids, alkalis, oxidizing agents, surfactants, and miscellaneous substances) to urine samples positive for amphetamine, 3,4-methylenedioxymethamphetamine (MDMA), tetrahydrocannabinol, heroin, cocaine, or benzodiazepines (diazepam or alprazolam) and tested them with one-component immunochromatographic UDST strips. The UDST for cocaine resisted adulteration the most, while the cannabis test produced the most false negative results. The most potent adulterant that barely changed the physiological properties of urine specimens and therefore escaped adulteration detection was vinegar. Besides lemon juice, it produced the most false negative test results. In conclusion, some urine adulterants, such as vinegar, could pass urine specimen validity test and remain undetected by laboratory testing. Our findings raise concern about this issue of preventing urine tampering and call for better control at sampling, privacy concerns notwithstanding, and better sample validity tests.
Highlights
Immunochromatographic strips for urine drug screening tests (UDSTs) are common and very suitable for drug abuse monitoring, but are highly susceptible to adulterants kept in the household, which can significantly alter test results
UDST devices are based on competition between a drug and a drug-dye conjugate for binding an anti-drug antibody immobilised on nitrocellulose membrane
Urine samples used in this study made part of those submitted to our toxicological laboratory for drug screening and were confirmed positive for one of the following substances: amphetamine, MDMA, tetrahydrocannabinol, heroin, cocaine, diazepam, or alprazolam (Table 2)
Summary
Immunochromatographic strips for urine drug screening tests (UDSTs) are common and very suitable for drug abuse monitoring, but are highly susceptible to adulterants kept in the household, which can significantly alter test results. The most potent adulterant that barely changed the physiological properties of urine specimens and escaped adulteration detection was vinegar Besides lemon juice, it produced the most false negative test results. If urine contains a drug above the cut-off level, the drug inhibits the drug-dye conjugate to bind to the antibody, and the result is positive (no line appears on the strip) Their many advantages notwithstanding, UDSTs suffer of some shortcomings as well, including low accuracy and specificity. They can produce false positive results due to cross-reactivity with other non-targeted drugs of similar chemical structure or certain food ingredients. They can produce false negative results if samples have been tampered with [11,12,13,14]
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