Drug testing is a common practice in various settings, including pre-employment screenings, ongoing workplace monitoring, and legal contexts. It identifies the presence of specific substances or their byproducts in biological samples. The goal of such tests is to ensure safety, maintain productivity, and comply with regulations. Test results can range from negative, indicating no detectable substances, to positive, showing the presence of drugs.
Understanding a Dilute Sample
A “dilute” urine sample refers to a specimen with a higher water content than typical. Laboratories assess dilution by measuring specific markers: creatinine levels and specific gravity. Creatinine is a waste product from muscle metabolism, and its concentration reflects urine concentration.
Specific gravity indicates the concentration of dissolved particles in urine compared to water. Normal urine typically has a creatinine level between 20 and 400 milligrams per deciliter and a specific gravity between 1.002 and 1.030. When a sample is dilute, its creatinine levels are lower (2-20 mg/dL) and its specific gravity is also lower (1.001-1.003). These low values signal the urine is less concentrated than expected.
Reasons for Dilution
Urine samples can become dilute for several reasons, some unintentional and others intentional. Unintentional dilution often occurs when an individual consumes a large amount of fluids prior to providing a sample, due to routine hydration habits. Certain medical conditions, like kidney problems, or the use of diuretic medications, can also lead to a dilute sample.
Conversely, intentional dilution involves deliberate actions to reduce drug metabolite concentration in urine. This might include consuming excessive liquids or adding water directly to the sample after collection. The aim is to lower drug concentrations below detection thresholds. However, laboratories employ validity checks to identify these attempts.
Interpreting a Positive Dilute Result
A “positive dilute” drug test means drug metabolites were detected, and the sample was also identified as dilute. This indicates that despite the high water content, the amount of drug metabolites present was still above established cutoff levels. Laboratories use specific cutoff levels, measured in nanograms per milliliter (ng/mL), to determine a positive result. Even with dilution, if the drug concentration surpasses this threshold, the test is considered positive.
A positive dilute result is generally treated as a confirmed positive drug test. This is because detectable drug metabolites, even in a diluted state, confirm exposure to the substance. For instance, the Substance Abuse and Mental Health Services Administration (SAMHSA) provides guidelines for federal workplace drug testing, including criteria for identifying dilute specimens and interpreting positive dilute results.
What Happens After a Positive Dilute Result
Following a positive dilute drug test, several actions typically occur, varying based on the testing context. Employer policies often dictate the next steps, ranging from requiring a retest to imposing disciplinary actions or withdrawing a job offer.
A Medical Review Officer (MRO), a licensed physician, reviews positive dilute results and contacts the individual to discuss any legitimate medical explanations. If no valid medical explanation is provided, the MRO reports the result as a confirmed positive. In some cases, especially if there is concern about intentional dilution, a retest might be ordered under direct observation to prevent further attempts at dilution. Legal or professional implications may also arise.