An In-Depth Look at the Weaknesses of Instant Urine Drug Tests
Instant urine drug tests are cost effective and convenient but they do have weaknesses.
In the past, employers were sometimes reluctant to engage in drug testing because of the time and costs that testing entailed. This in spite of anecdotal and statistical evidence suggesting that substance abuse does play a role in many workplace accidents. (Learn more in "Prescription Opioids and Safety Sensitive Work".) One study suggests that more than 10 percent of workplace fatalities can be attributed to on-the-job alcohol consumption. Prospective and current employees had to go to a testing facility where they either submitted to a urine or blood screen, and then there was generally a multiple day wait before results are available.
The costs of these tests were also high. Estimates suggest that costs generally range from $30-$50, although many variables play a role in these costs. For example, employers who are testing large numbers of individuals are likely to pay lower costs per test than an employer who only screens a handful of employees each year.
However, the emergence of a wide variety of instant urine drug tests on the market has fundamentally altered these cost and time calculations. With an instant urine drug test, which integrates sample collection and testing in one simple cup, testing can be immediately performed in a company’s office and results are available in a matter of minutes.
These instant drug tests not only save employer’s and employees’ time, they are also far more cost effective than traditional tests. A simple 3 panel screen, for example, will cost a company well under $5 per test, and even a much more sophisticated 14 panel test runs less than $15 (and these costs are likely to be even less for large companies that buy these testing supplies in bulk). Some specialists in this field suggest that test prices are likely to come down even further in the near future, as more and more companies crowd the market with their products.
Note that the panel number refers to how many metabolites (and associated drugs) the test will be screening for. For example, 3, 5, 10, 12, or 14. (Learn more in "Drug Test Types: 5, 7, and 12 Panel Urine Screening Differences and Reasons to Use".) A 5 panel screen tends to be the standard named in government regulations such as for DOT testing.
Even though there are definite positives associated with these instant drug screens, primarily time and cost savings, some employers do have concerns about adopting this new technology. The principal concern tends to be the question: Are instant urine drug tests as accurate as other tests?
Weaknesses of Instant Urine Drug Tests
To address this concern with instant drug tests, the U.S. Food and Drug Administration (FDA) has conducted extensive reviews of instant drug screens that may be used in workplaces, as well as by parents who may be concerned that their child is using illicit substances. This review generally suggests that the tests are quite accurate at detecting the presence of a wide range of substances (drug metabolites) in the tested urine.
However, this comes with several caveats.
First, because of the high degree of sensitivity of many of the tests, some tests will yield a false positive. A false positive occurs when the test indicates that the individual has used a drug even though they have not. Second, these tests do not indicate the amount of the drug in the urine or how recently a drug has been used, only that it was used at some point in the testing window during which the metabolite would still be in the urine. And finally, there is a risk of user error skewing the results.
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The Problem of False Positives
In addition to the potential sources of error noted above, there are some other factors that may lead to false positives. For example, some common over-the-counter cold and allergy medications may contain ingredients that would trigger a positive result for methamphetamines. The metabolites from these antihistamines closely resemble the metabolites from methamphetamines. Several antidepressants, most commonly Wellbutrin, may also lead to a false positive test result for methamphetamines. In addition to false positives for methamphetamines, there are some prescription medications that may cause false positives for opioids, marijuana, and cocaine.
For example, quinine, which is an anti-malarial drug used to treat malaria as well as auto-immune diseases such as lupus, can trigger a positive result for opioids.
Even though these false positives from pharmaceuticals represent only a tiny fraction of all drug screens, the costs of being falsely accused of using drugs can be gigantic. Therefore, it is important to have procedures in place to deal with legal medication false positives, such as the regulations under DOT testing that use a Medical Review Officer as a safety valve for dealing with these issues. (Learn more in "8 Things Employers Should Know About DOT Drug and Alcohol Testing".)
In addition to pharmacological interactions leading to false positives, there are other potential triggers for a false positive. Something as seemingly random as the food that a person eats before they provide their urine sample may also generate a false positive. Perhaps the most well-known of these food suspects is poppy seeds. Studies suggest that a poppy seed roll or bagel could only potentially trigger a false positive opioid result for less than 24 hours after consumption. After that, the metabolites in the urine would be below threshold levels.
However, to mitigate the risk of this false positive, many employers, particularly government agencies, have raised the minimum threshold of opioid metabolites in the urine that will screen as a positive result.
Most reputable websites suggest that there are approximately 5 – 10 percent false positive results from instant urine drug tests. Although this number is not particularly high, it is high enough to be concerning.
The Problem of False Negatives
Perhaps equally concerning, there is also a large number of false negative results from these tests. Statistics suggest that the percentages on this end are even higher, 10 – 15 percent. A false negative happens when the instant screen fails to identify someone who has used one of the drugs that is being tested for. A false negative may happen for numerous reasons. For example, it may take several hours for a drug metabolite to make its way into the tester’s urine. Therefore, there is a gap between use and a positive test. Similarly, drug metabolites do not remain in the user’s urine indefinitely. After several days (with the exact time frame varies from drug to drug), the drug metabolite will have passed out of the individual’s system and he/she will return a negative screen.
Also, if the quantity of the drug used was relatively small, it may not be enough to generate a positive result. Also, a false negative may happen if the person giving the sample tampers with the test. (Learn more in "Top 3 Ways Employees Try to Cheat Drug Testing".) There are numerous ways to try to fake a drug test, including diluting urine with water from the toilet or adulterating the specimen by adding chemical agents, such as bleach, to a test sample. However, more sophisticated tests will clearly show when a test has been maliciously tampered with, since specific gravity and/or creatinine levels will be outside of normal bounds.
Mitigating the Weaknesses
In spite of these weaknesses, instant urine tests still have a relatively high degree of accuracy of these home/workplace tests, generally estimated at upwards of 90 percent. To combat the weaknesses however, the FDA recommends that any positive initial screen be sent to an approved laboratory for confirmation. (Learn more in "Three Types of Drug Testing: What Employers Should Know About Lab Testing, POCT, and Express to Lab Testing".) These confirmation tests use a more sophisticated screening methodology than initial tests.
The initial tests use a process referred to as immunoassays, whereas the follow up tests uses Gas Chromatography Mass Spectrometry, more commonly referred to as GC-MS. Scientists contend that the false positive probability for a GC-MS test is well under 1 percent.