Yes, a rapid drug test can give a false positive screening result. This means that the test gives a positive result even though the confirmation method does not detect the drug in question or its metabolite. The reason may be, for example, a test-specific cross-reaction, a factor related to the sample, or testing that deviates from the instructions for use.
A positive rapid test result is a preliminary screening result and does not alone prove the use of narcotics.
What can cause a false positive result?
The immunological rapid test is based on the reaction between the antibody and the compound identified by the test. A compound with a similar structure can cause a cross-reaction in some tests.
Cross-reactivity is test-specific. Medicines and other compounds do not affect every drug test in the same way. A general medication list cannot establish whether a particular test result is a false positive.
Check the user manual for the test used:
- which substances the panel detects
- the panel cutoff
- the cross-reactivity reported by the manufacturer
- when to read the result
- the limitations of the test
Do not stop prescribed medication because of a rapid test result without advice from your healthcare professional.
Can incorrect testing affect the result?
Yes. Factors affecting reliability include:
- an incorrect sample type
- an expired or incorrectly stored test
- sample contamination
- reading the test too early or too late
- an incorrect sample volume
- a missing control line
If the control line does not appear, the result is invalid. Repeat the test according to its instructions; do not interpret it as positive or negative.
What should you do after an unexpected positive result?
Check that the correct sample was used and the result was read within the time stated in the instructions. Check the expiry date, storage conditions and reported cross-reactivity.
Repeating a rapid test may reveal a testing error, but a second rapid test is not a confirmatory method. If the result could have medical, legal, employment or other significant consequences, confirm the screen with an appropriate laboratory method.
Can a drug test also give a false negative?
Yes. A negative result may occur when:
- the concentration is below the test cutoff
- the sample is collected outside the detection window
- the sample is heavily diluted
- the selected panel does not detect the substance
- the procedure or reading time does not follow the instructions
A negative screening result does not indicate with certainty that no narcotics have been used.
How do I choose a suitable Testerit.fi rapid test?
When you want to screen several groups of substances with the same sample, you can find options in Testerit.fi’s multi-drug screens. Always check the product’s panel list, sample type and intended use.
If you want to screen a cocaine metabolite separately for professional use, there is an individual cocaine test for a urine sample. Check the product page for the intended use, limit value and manufacturer’s instructions for use.
See the entire selection of Testerit.fi’s rapid drug tests. For more information on the limit value and the interpretation of test lines, see How does a rapid test work?
More information on test types, detection times and interpretation of results can be found at the drug test info.
