Drug Testing – False Positives for Urine Testing
A false positive urine test result can have three possible sources:
(1) See Drug False Positives Chart Below
(2) False Positive: Now What do I do? Learn Steps to Resolve
Prescription Drugs: Many prescription drugs have a high potential for abuse and, thus, are targeted by urine tests. Upon testing positive for a prescription drug, you will be required to provide proof of prescription in your own name. Once confirmed, your positive result will be considered false and will be reported as a negative result. If proof of prescription is not provided, it is assumed that the drug was taken illegally and a true positive result will be reported.
Administered Drugs: This includes drugs administered by a medical professional during an office visit or surgery. For example, Morphine is often administered to relieve pain during surgery. Some administered drugs are also commonly prescribed. Like prescription drugs, many administered drugs have a high potential for abuse and are targeted by urine tests. Always be aware of drugs administered during an office visit or surgery. You may want to test yourself in advance of a work related drug screen to see if you show positive for anything. If a drug test is on the horizon, request documentation of all medications used during your visit. Upon testing positive for an administered drug, you will be required to provide medical documentation in your own name. Once confirmed, your positive result will be considered false and will be reported as a negative result. If medical documentation is not provided, it is assumed that the drug was taken illegally and a true positive result will be reported.
Cross-reactions: A cross-reaction occurs when a substance is misidentified as a targeted drug/metabolite by a urine test. Such substances are known as cross-reactants. They are usually very similar in chemical structure to a targeted drug/metabolite. As a result, they can be misidentified and cause a positive result. Cross-reactants come in many forms – over-the-counter medications, food items, etc. What makes a substance a cross-reactant is simply the fact that it can be confused with a targeted drug/metabolite. Note however, that cross-reactions have become less common. In the past, the drug testing industry has received bad publicity for high cross-reaction rates. As a result, most manufacturers have made significant improvements. Cross-reactions can still occur. Yet required cutoff concentrations are usually too high to register occasional usage. When a cross-reaction does occur, it is often the result of abusive consumption patterns. Any claim that a positive test result was caused by a cross-reactant will be met with skepticism. See below section What to do if you test positive and know that your were drug-free.
Who should be concerned about false positives:
Prescription drug users need not be concerned, as long as the prescription was obtained legally. Do not discontinue using legally prescribed medications. Also, administered drugs should not be an issue, as long as you can provide medical documentation if requested. However, everybody should be concerned about cross-reactants, as their use can be difficult to substantiate. In fact, cross-reactants (not legal prescriptions) should always be viewed in the same light as illegal drugs. With that in mind, individuals not using a detoxing agent are at the greatest risk of long-term detection. The detection time for a cross-reactant will usually approximate the detection time of the drug mimicked. Individuals using a detoxing agent are at a lower risk, as an effective detoxing agent will eliminate all drugs/metabolites from the body, including those that might cause a false positive. However, cross-reactants should still be avoided for the time period specified by the instructions for the detoxing agent. For example, if the instructions specify to avoid toxins for at least 24 hours, then avoid cross-reactants for at least 24 hours as well.
Filling out the Consent Form:
Filling out the urine test consent form: Most labs provide a space on their urine test consent form to record your prescriptions. Some use broad enough wording to allow you to also include over-the-counter medications used recently and/or drugs recently administered by a physician. If you are otherwise drug-free and are not using a detoxing agent, you
should record such substances on the form. If you subsequently test positive, you will then have the basis for an appeal. On the other hand, if using a detoxing agent, it is wise not to record such substances on the consent form. The Medical Review Officer (MRO) may become suspicious if you subsequently test negative for a drug that you had listed on the form. In any event, avoid listing any substance that is not a medication, such as poppy seeds, as this may alert the MRO that you have been studying the subject. If you have any doubt you may test positive, test yourself in advance.
What to do if you test positive and know that you were drug-free:
Upon reviewing a positive test result, the MRO will usually contact you by phone. If you tested positive for a prescription or administered drug, the MRO will request medical documentation. A follow-up test may also be required. In the absence of medical documentation or if you tested positive for an illegal substance, the MRO should determine if a legal cross-reactant was involved. Help him. Begin by insisting that you were drug-free and that the test results must be wrong. You can mention the cross-reactant that you suspect caused the false positive. But avoid sounding too knowledgeable on the subject. Wait to see what the MRO says. He might simply ask for proof that you used the cross-reactant and/or a legitimate purpose for using it. But this is rare, as MRO’s are always skeptical about such claims. He should schedule a more thorough follow-up test. If not, insist on it. Initial test results usually identify only the drug category that tests positive (ie. Amphetamines or Barbiturates) – not the specific drug within that drug category. You have the right to know what specific drug caused your positive result. Gas chromatography/mass spectrometry (GC/MS) is about the only method that can pinpoint the specific source of the positive result. Standard testing procedures normally require a follow-up test following any initial positive screening. Though many companies will avoid using GC/MS because it is quite expensive. Unfortunately, it is the only method that can prove your innocence.
The below chart attempts to cover all possible sources of a false positive urine test result. Substances listed in the right column may cause a false positive for the drug/metabolite shown in the left column. Brand names are shown in brackets. Note that prescription drug and administered drug positives are considered false only when medical documentation is provided.
Detection Period for different types of Drugs
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Since false positive study information is limited, we cannot guarantee the validity or completeness of this data. And since urine testing accuracy has improved over the years, some entries may be outdated. In addition, some prescription drugs listed may or may not be legal in the United States or abroad.
Reported false positives are not associated with any particular manufacturer’s urine screen. They are provided as a general guideline in an attempt to cover all possible examples.
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