What Are Drug Test Strips?
Drug Test Strip is made up of either paper or plastic used to screen for the presence of drugs in the biological specimens such as urine or blood. The strip has chemical pad or reagents which when comes in contact with the biological specimen reacts or changes color. It works on the principle of competitive binding of the drug substance and/or its metabolites to the testing strip.
Most commonly used biological specimen for drug testing is urine. Drug testing strips are one of the most economical and safe ways to screen for drug misuse or dependence. There are single drug test strip kits to multi-drug test strip kits available in the market. People can choose single drug test strip kit to check for any one particular drug or multi-drug test strip kit to check for different drugs at the same time at the comfort of their house or any other place.
How Does Drug Test Strips Work?
When drug testing strips are immersed in the urine specimen, specific immunochemical reaction takes place between the antibodies and antigens to break down particular chemical compounds in the specimen. The assay depends on the principle of competitive binding of the antibody between drug conjugate and free drug that may be present in the tested urine sample.
When there is presence of any drug in the urine specimen, it competes with the conjugate of the drug for a determined quantity of antibody dye conjugate. When the drug amount is equal or more than the cut-off level, the binding of drug conjugate to the antibody will be prevented. Therefore, when the urine sample tests positive for a drug, the colored band will not show up on the test line zone. The appearance of a colored band indicates either no drug or the amount of drug is less than the standard cut-off level.
For instance, when screening for any drug such as THC, OPI or MAMP in the urine specimen, the presence of any drug would make it to contend with the drug conjugate for a determined quantity of the antibody dye conjugate. If the amount of the drug detected is equal or more than the cut-off level, the binding of drug conjugate to the antibody will be prevented and hence stopping the coloring of the band; thus indicating a positive result. If no drug is detected, binding of the drug conjugate to the antibody will take place and the band in the test line zone will get colored, indicating a negative result.
When the drug test strip is immersed in urine sample, a colored band will appear in the Control Region. This indicates that the test is performed appropriately. A colored band in the Test Line Region is interpreted as a negative result (no drugs present or the amount of drug present doesn’t meet the standard cut-off level). No occurrence of colored band in the Test Line Region indicates a positive result (presence of drugs).
If there is no appearance of any colored bands in any of the regions, you can try re-dipping the strip(s) again in the urine specimen for a few more seconds and check if the colored bands appear. Even after the second attempt if no colored bands appear, then the test is considered to be invalid.
Preliminary positive results can be confirmed with a more specific alternative testing method such as gas chromatography/mass spectrometry (GC/MS).
Therefore, a drug test strip is a preliminary method that can only indicate if the donor is positive or negative for drug(s).
Accuracy Of The Drug Test Strips
Screening with drug test strips is very accurate and the sensitivity levels conform to the United States Substance Abuse and Mental Health Services Administration (SAMHSA) standards and the levels set are as recommended by the National Institute on Drug Abuse (NIDA). However, there is also a possibility of false results due to the cross reactions occurring with other substances present in the urine.
Bottom Line
Drug test strip is a rapid, qualitative immunoassay for screening any selected drug(s) in biological specimens. It is used for in vitro diagnostic purposes only. It displays either a positive or a negative result. Interpretation of alcohol strip results is done by comparing the colors of the reaction pad.
Drug test strip is a rapid and more cost-effective preliminary method of testing. To confirm preliminary positive results, alternative testing method such as gas chromatography/mass spectrometry (GC/MS) can be performed.
It is advisable to read the instructions provided along with the drug test strip kit before commencing the test. The test must be carried out carefully to avoid contamination since these drug tests are very sensitive and can lead to inaccurate test results.
In other scenarios, one must reveal if they are taking any prescription drugs for medical conditions or over-the-counter medications before being tested rather than later.
