Drug test results are not always a simple positive or negative. Sometimes, a test yields an “abnormal” result, indicating a more complex outcome than just the presence or absence of a substance. These findings require further investigation to understand what occurred during collection or analysis. Understanding these classifications is important for anyone undergoing or interpreting drug screenings.
Understanding Abnormal Results
An initial drug screen might first be categorized as “non-negative,” which means the preliminary test indicated the possible presence of a drug or its metabolites, requiring further confirmatory testing. Samples can be labeled as “diluted” when the urine specimen contains more water than a typical sample, making it difficult to detect drug presence accurately. Diluted urine can have low creatinine levels, a waste product that indicates urine concentration.
A “substituted” result implies that the sample provided is not consistent with human urine, meaning it may have been replaced with another liquid or someone else’s urine. This is often identified by significantly diminished or divergent creatinine and specific gravity values. When a foreign substance is added to a sample to mask drug presence, it is termed “adulterated.” These substances can chemically alter the sample to interfere with test results.
An “invalid” result occurs when the laboratory cannot obtain a clear positive or negative outcome from the specimen. This can happen due to interference from unidentified substances, abnormal physical characteristics of the sample, or issues during the collection or testing process that prevent a reliable result. Such a result indicates that the sample is unsuitable for testing, but it does not automatically imply tampering.
Common Reasons for Abnormal Results
Several factors can contribute to abnormal drug test results, often from legitimate circumstances or unintentional actions. Prescription medications frequently lead to non-negative results because many drugs share chemical structures with illicit substances. For instance, some ADHD medications and diet pills like phentermine are chemically similar to amphetamines, potentially causing a false positive. Certain antidepressants, such as bupropion, can also trigger false positives for amphetamines or methamphetamines.
Over-the-counter (OTC) medications and supplements can also interfere with drug tests. Common cold and allergy medicines containing pseudoephedrine or diphenhydramine might be misinterpreted as amphetamines or methadone. Even widely used pain relievers like ibuprofen and naproxen have been associated with false positives for barbiturates or THC in some cases. Dietary factors, particularly poppy seeds, are well-known for causing false positives for opiates like morphine and codeine due to trace amounts of these compounds.
Medical conditions can influence urine concentration and composition, potentially leading to abnormal results. Kidney disease, for example, can affect creatinine levels and urine concentration, while diabetes can alter urine pH. Sample dilution can occur when individuals consume excessive fluids, either intentionally to “flush” their system or due to high hydration habits. Errors in collection or laboratory handling, such as mislabeling or equipment malfunction, can also contribute to invalid results, though these are rare with proper protocols.
The Confirmation and Review Process
When an initial drug screen yields a non-negative result, a confirmatory test, typically Gas Chromatography/Mass Spectrometry (GC/MS), is performed. This technique is highly specific and accurate for identifying and quantifying substances in a sample. GC/MS separates compounds within the urine and identifies them by their unique molecular fingerprints, distinguishing between structurally similar compounds that might cause false positives in initial screens. This method verifies the presence of drugs or their metabolites at specific levels.
Following confirmatory testing, especially for positive, adulterated, substituted, or invalid results, a Medical Review Officer (MRO) becomes involved. An MRO is a licensed physician with specialized training in substance abuse disorders and drug testing regulations. The MRO reviews laboratory results and evaluates any medical explanations for the findings.
The MRO’s primary responsibility is to contact the individual whose test yielded an abnormal result. During this confidential conversation, the MRO inquires about any legitimate medical reasons, such as prescription medications, over-the-counter drugs, or dietary intake, that could explain the initial finding. If a legitimate medical explanation is provided and verified, such as a valid prescription, the MRO can then report the initial “non-negative” result as a “negative” to the employer or requesting entity. This step ensures fairness and accuracy by considering all medical factors.
Strategies for Accurate Testing
To minimize abnormal drug test results, individuals can adopt several strategies. Providing honest and complete disclosure of all medications, including prescription drugs, over-the-counter remedies, and supplements, to collection site personnel or the MRO is important. This information allows for proper evaluation of potential interferences and helps interpret results accurately. Maintaining adequate hydration is beneficial, but excessive fluid intake should be avoided, as it can lead to a diluted sample.
Individuals should avoid products marketed to “cleanse” or “beat” drug tests, as these often involve adulterants that can lead to an adulterated or invalid result. Laboratories employ specimen validity testing to detect tampering attempts, often by checking pH levels, specific gravity, and creatinine concentrations. Understanding that different test types, such as urine, hair, saliva, and blood tests, have varying detection windows is also useful. Adhering to all instructions provided by collection site staff is important, as proper procedure helps ensure sample integrity and accuracy.