US Drug Test Centers Blog

False Positives: What Does It Really Mean?

Posted: Sep 14 2016

By: Ashlee Arnold

For the people who are busy monitoring offenders for the court, child services, or even the few that have human resource positions or background checks, there are times when a false-positive can occur. What does a false-positive really mean? How do you treat the subject being tested or the sample? This may help answer a few questions and may even help you consider contacting your laboratories that handle retesting if a sample is considered a false-positive.

According to, a false-positive is "any screening test result that incorrectly detected or classified a person or thing; a test result that is incorrect because the test indicated a condition or finding that does not exist." This is a fairly accurate description that is legally viable in any court. False-positives do occur because no test is completely infallible. However, there should be protocols in place that disprove contesting the results.

Looking at the basic opportunities for false-positives would be from an individual providing an oral swab for an employment opportunity. There should be standard operating procedures in place at any workplace that has human resources personnel drug testing individuals for a work placement that avoid any reading of oral swabs in front of the applicants. Human resource personnel who are handing out oral swabs should be certified for proper handling of specimens, no matter how trivial the sample.

People who are handling any bodily fluids should be certified in handling biohazards and understand infectious diseases. No matter how trivial it might be when doling out oral swabs, you need to be aware that an oral sample can contain any number of infectious diseases including tuberculosis, candidiasis (thrush) that is a fungal infection, Coxsackie A16 (hand, foot, mouth disease).

We spend a good portion of our days with our hands on, in, or near our mouths and eyes. On average, subconsciously, humans habitually touch their faces between 16 to a thousand times in a day. If you are handing out oral swabs and not following proper protocols that protect you and the donor, you are at risk of any number of infections.

cup of cotton swabsOral swabs are very unlikely to produce a false-positive. If the donor has exposure to any of the tested samples on the oral strip, it is likely they are positive for any number of drugs. When there are procedures in place that avoid the human resource personnel in the uncomfortable position of having a positive test come up while the donor is present, a false-positive will never happen. If an oral swab, when handled correctly by experienced and certified personnel, comes up positive, it means the donor was "hot" for whatever the panel test shows.

While skin tests are less likely to show false-positives, there should be considerations and procedures in place when dealing with individuals who provide a skin swab. Likely there are very young children who are subjected to skin swabs. If their swab is positive, it is highly unlikely there is any doubt about the results. However, often when children are present at the time their parents are consuming marijuana or methamphetamines, or any free-based narcotic that can be inhaled, those particles will adhere to skin and hair. Any time someone is present to cigarette smoke they are exposed to the smoke clinging to their clothes, skin, and hair.

Children will not dispute the results; however, the parents who exposed their children to the illicit substances will declare the test was wrong, demand a retest, or have an attorney attempt to dismiss any collected evidence that challenges the parental rights. Since it is unlikely a retest can be performed after the initial results, child service workers should always request an agency assist when it comes to testing children in an environment that could be volatile. While a urine analysis is not likely to happen for the children or parents, it is possible an oral swab may validate the skin swab, although if the child was not in immediate proximity at the time of the use, the sample would be negative.

childs eyesIndividuals who most often dispute the positive urine analysis are court-ordered or probationary defendants. People will go to great lengths to avoid a drug test. Some people will attempt to drink small quantities of bleach because they were wrongly convinced the flushing of bleach through consumption will clear their results. When dealing with defendants or people who are court ordered to supply a random urine analysis you need to monitor the offenders carefully. It may be embarrassing or uncomfortable for both parties to be present at the time of the urine analysis, but if your responsibility is to be present at the time of the sample, do not become complacent. People who have gotten away with false samples will continue to have friends or family members supply urine for them to use during the test.

If someone provides a sample that is positive and they refute the obvious, it's their right to have the sample retested. It's very important that the sample they provided is not allowed out of the donor's sight or the collector's sight. The sample should be sealed with an evidence tag and have a chain of custody form immediately filled out. The sample will need to be retested at a designated facility predetermined and at the donor's consent. The donor should be responsible for any additional costs attributed to the retesting of the sample.

If the sample tests come back negative for results that showed in the specimen cup, that does not mean the original sample was negative. Likely the donor supplied a sample that was "hot" for any of the panel tests. What is likely happening is the testing facility is using a standardized retest level that is not as low as the specimen cup. What can happen, without anyone realizing, is the cut-off levels are not the same.

Often the facility will have a testing cut-off that is not as low as the specimen cups. It is important that both the specimen cup and the testing facility use identical cut-offs for testing. This will diminish any false-positives exponentially. If you are receiving conflicting results from the retest, contact the facility immediately to make sure the cut-off levels are identical to the specimen cups.

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