Read a drug test according to the instructions for that specific product. A positive screen indicates that the targeted substance or metabolite may be present at or above the test cutoff; it does not establish impairment or prove drug use. A negative screen applies only to the substances, cutoffs and sample tested. Check the control line and reading window before interpreting a result.
What does a positive drug test result mean?
A rapid drug test provides a preliminary screening result. A positive screen needs laboratory confirmation when the result is unexpected or will have significant medical, employment or legal consequences. Review the sampling conditions, medicines and other relevant information with an appropriately qualified professional.
Many rapid drug screens use a competitive immunoassay. With a valid control line, a visible test line, including a faint line within the reading window, generally indicates a negative screen; an absent test line indicates a positive screen. An absent control line means the result is invalid. Always follow the product’s instructions.
A positive screen calls for further assessment. It is one part of the assessment and cannot establish the timing of use, dose or impairment on its own.
What does a negative drug test result tell us?
A negative drug test result indicates that the substance being tested was not detected in the sample at levels above the test threshold. A negative result only applies to the substances identified in the test, the sample in question and the reported limit values. It does not prove non-use and does not exclude substances not included in the test or any other time. A negative result does not rule out all possibilities, as the detection time depends on several factors.
The detection time is affected by, among other things, the substance being tested, the amount used, the frequency of use, and individual factors such as metabolism and hydration status. Some substances are eliminated from the body quickly, in which case they can only be detected within a short window of use.
Interpret a negative screen in the context of the sampling time, detection window and test method. It cannot establish abstinence.
What is a false positive result and how does it occur?
A false positive screen is a preliminary positive result that is not supported by appropriate confirmatory testing for the target substance. Cross-reactivity can be one cause, but it depends on the particular test and concentration. Check the product’s instructions and discuss unexpected results with a qualified professional.
Check the limitations and cross-reactivity information in the instructions for the specific test. A general list of medicines cannot determine whether a substance interferes with that product at its cutoff. Do not stop a prescribed medicine because of a screening result without consulting the prescriber.
Use appropriate laboratory confirmation before drawing significant conclusions from a positive screen. Confirmation uses a method that is more specific for the target substance than the initial screening assay.
How do different sample types affect interpretation?
The sample type affects the detection window and the question the test can answer. Urine, oral fluid and hair results cannot be interpreted as interchangeable measures of use or impairment.
Urine and oral fluid tests
Urine tests may detect a drug, its metabolites or both, depending on the assay. Oral fluid testing is often used to investigate more recent exposure, but a result alone does not establish impairment. Supervised sample collection can reduce opportunities for tampering. Check the target substances and intended use of the specific product.
Hair tests and other methods
Laboratory hair analysis can investigate exposure over a longer period, depending on the sample length and analytical method. Surface, material and drink tests investigate the material tested; they do not determine whether a person has used a drug or is impaired. Use each product only for the sample types and substances specified in its instructions.
Choosing the right sample type depends on what information is needed in the situation. Testerit.fi’s selection of drug tests includes several different test methods for different uses.
When should a drug test result be confirmed in a laboratory?
Confirm a preliminary positive result using an appropriate laboratory method before making significant medical, legal or employment decisions. In Finland, section 19 of the Occupational Health Care Act requires a positive drug test result for a job applicant or employee to be confirmed in a quality-controlled laboratory. Requirements in other countries depend on local law and the testing setting.
Laboratory confirmation is particularly relevant when:
- The result could affect employment, legal matters or another significant decision.
- A medicine or supplement may cross-react with the particular screening test.
- The result conflicts with the clinical history or other relevant information.
- Sample quality or the test procedure may have been compromised.
Appropriate confirmatory laboratory methods can distinguish the target substance from potential interfering compounds more specifically than an initial screen. Interpretation still requires the sampling details, method and clinical context. Consult a qualified healthcare professional about an unexpected result.
The correct interpretation of the results of a drug test requires both careful adherence to the instructions of the test and evaluation of the results as part of a broader overall situation. Check out Testerit.fi’s selection and choose the test method that suits your purpose.
More information on test types, detection times and interpretation of the results can be found at the drug test info.
