Drug tests are often required for employment, legal, or medical purposes. While most yield clear positive or negative results, some are “inconclusive.” An inconclusive drug test means the laboratory could not definitively determine if a substance was present or absent in the sample. This outcome is not a failed test, but indicates that further investigation or retesting is necessary.
Sample Integrity Issues
The physical state and composition of a sample significantly influence drug test results. Dilution is a common issue, occurring when excessive fluid intake lowers drug metabolite concentration below detectable thresholds. This can lead to an “invalid” or “inconclusive” result, often identified by low creatinine levels or specific gravity. Laboratories employ methods to detect dilution, whether before or after collection.
Adulteration involves attempts to tamper with a sample by adding foreign substances. These substances, such as bleach, soap, or commercial adulterants, can alter the sample’s chemical properties like pH or specific gravity. Such alterations flag the sample as inconclusive or invalid, as they interfere with the test’s ability to accurately detect drug metabolites. A sample might also be deemed invalid if its temperature is incorrect at collection or if it exhibits extreme pH levels inconsistent with human urine, suggesting potential tampering or an unusual physiological state.
Interfering Substances
Certain substances, other than illicit drugs, can interfere with drug tests, leading to inconclusive or false positive results. Prescription medications are a common cause, as some drugs like antidepressants, pain relievers, or ADHD medications, have chemical structures similar to illicit substances or interact with test reagents. For instance, bupropion, an antidepressant, may be flagged as an amphetamine or methamphetamine.
Over-the-counter (OTC) medications and dietary supplements also cause issues. Common OTC pain relievers like ibuprofen, certain cold medications containing pseudoephedrine, or cough suppressants with dextromethorphan, might lead to inconclusive results. Some dietary supplements, including hemp products or herbal remedies like St. John’s Wort or kava, could affect test accuracy. Even certain foods, such as poppy seeds, are known to contain compounds that can result in inconclusive readings for opiates.
Laboratory and Collection Challenges
Issues within the testing process, from sample collection to laboratory analysis, can contribute to an inconclusive drug test result. Errors during sample collection, such as improper handling, insufficient sample volume, or labeling mistakes, can compromise specimen integrity. Each step of the collection and handling process is documented through a “chain of custody,” and any break in this record can invalidate test results.
Laboratory equipment can malfunction or require recalibration, leading to inaccurate readings and inconclusive outcomes. Human error in the laboratory, including misreading results, incorrect sample preparation, or data entry mistakes, can also occur. Drug tests operate with specific detection thresholds, or cut-off levels. If a substance is present in very low concentrations, perhaps due to metabolism or time elapsed since exposure, it might fall below the cut-off, leading to an inconclusive range.
Interpreting and Addressing the Result
An inconclusive drug test result signifies the sample could not be definitively categorized, requiring further action. This outcome is not a failed test, but necessitates retesting or additional investigation.
Next steps often involve retesting, sometimes with a new sample or a more sensitive method like Gas Chromatography-Mass Spectrometry (GC-MS). GC-MS is a “gold standard” for confirmation due to its high specificity and accuracy. Individuals may also be asked to provide medical documentation for any prescription medications that could have interfered with the test. Communication with the testing facility or the requesting entity is advisable to understand the reasons for the inconclusive result and required follow-up procedures.