Effect of urine adulterants on commercial drug abuse screening test strip results

Urine drug concentrations and UDST results obtained before adulteration are presented in Table 2. Table 3 shows how the tested adulterants affected UDST results. Vinegar (9 % acetic acid) turned nearly all UDST results false negative, with the exception of cocaine. Lemon juice followed suit in tampering, save for cocaine and opiates. Other adulterants were less efficient. Many of the adulterants invalidated the UDSTs, led by Cevtok (30 % NaOH), which invalidated all of them.

Control drug-free and drug-positive urine samples tested with URIT 11G urine reagent strips and pH strips before adulteration showed similar findings suggesting maintained sample integrity, as expected (Table 4). After adulteration, however, URIT 11G urine reagent strips and pH strips revealed manipulation with some urine samples. WC Sanitar (9 % HCl) raised ascorbic acid levels compared to control and rendered the sample invalid due to compromised blood in urine values, plus it did not pass the pH strip test (see bolded values in Table 4). Vinegar (9 % acetic acid), lemon juice, and citric acid did change parameter levels of the URIT 11G test but not enough to reveal tampering. The pH test strip, however, did reveal tampering with lemon juice and citric acid. Cevtok (30 % NaOH) rendered URIT 11G test strips invalid on nearly all parameters and failed the pH strip test. Varikina (bleach; 5 % NaOCl), in contrast, passed undetected, even though it did test positive for nitrite presence and raised urine blood cells count. Asepsol invalidated the sample over protein values. Primosept GA (8 % glutaraldehyde) also rendered the sample invalid over high ketone values. Visine^® eye drops, in turn, passed undetected.

To the best of our knowledge, until this study of ours, no one has reported research data about household chemicals interfering with urine drug test results. Many of the household chemicals used as adulterants in this study are available in other countries in the region and beyond, and our findings could be useful anywhere.

Urine collection for laboratory drug testing is still not completely regulated in Serbia, and no one knows how many urine samples have been collected without supervision. Even though there are no test strips to test urine for specific adulterants, URIT 11G and pH test did detect adulteration by five household chemicals. Both have their limitations, though. The pH test strips are limited to changes in pH, whereas the URIT 11G test strips have a narrow pH range.

In terms of tampering, our study shows that the UDST for cannabinoids is susceptible to urine adulterants, as it yielded six false negative results. This is in line with earlier reports of immunoassay tests for cannabinoid detection (radioimmunoassay – RIA, enzyme immunoassay – EIA, and fluorescence polarisation immunoassay – FPIA) being the most susceptible to adulteration (24, 25). The UDST for amphetamine was also affected by adulterants (five invalid tests and three false negatives). In contrast, the UDST for cocaine was resistant to most adulterants (no false negative results), which has also been reported by Schwarzhoff and Cody (24). However, Asepsol, Primosept GA, and Cevtok did invalidate the test.

The most effective adulterants were acids and alkalis. They probably act through changes in pH and enable drug-antibody binding (26). Vinegar was the most successful in producing false negative results, save for the cocaine test, and did not affect the URIT 11G test results enough to be detected. As it were, its finding of elevated ascorbic acid could be interpreted as a result of high vitamin C supplement intake. Its masking properties have already been reported for immunoassays such as FPIA and EIA for some drugs (11, 24, 25, 26, 27). In contrast, the least efficient adulterant in our study were the Visine^® eye drops, as they did not change any of the original UDST findings, not even for cannabinoids, even though other reports say that it strongly interfered with immunoassays (FPIA, EIA, RIA) for the presence of cannabinoids (11, 25, 26, 27). To sum up, most of the investigated adulterants have the ability to change positive UDST strip results into false negative or render them invalid. In that respect vinegar and Asepsol stand out, as they can remain undetected even by experienced laboratory personnel.

In order to detect urine adulteration where test strips for urine adulterants are not available, urine samples should be checked not only with biochemical test strips such as URIT 11G and pH test strips but also visually and for warmth (if checking immediately after taking the sample), to see if they have been tampered with. Our study calls for more efficient screening methods for detecting sample manipulation. But maybe even more important is to develop drug screening methods, immunochromatographic or other, that will be more or even completely resistant to adulterants. In the meanwhile, urine should be collected by competent institutions in so-called “dry toilets” to ensure the integrity of the specimen and still protect the privacy of the person tested.

Utjecaj adulteranata u mokraći na nalaze komercijalnih testnih traka za otkrivanje zloporabe droga