• False Positives and False Negatives: What they are and how you get them in Drug Screening

    drug screening kit- drug test kitDue to the growing number of illegal substance users around the world, rapid, on-site drug screening tests has become very popular in offices, homes and schools. This type of drug screening test is more affordable and more practical, since sample collection can be done anywhere and test results can be read within minutes.

    The downside to this type of drug screening procedure, however, is that a few results may yield a false positive or a false negative. These uncanny results may render the test invalid and can allow drug users to go scot-free or even taint an innocent man’s name. Some companies may even be brought to court because of actions that stem from incorrect results. Thus, it’s important to understand how drug screening tests can yield false positive or false negative results.

    Although false positive results are said to have a rare occurrence of about 1 to 2.5%, drug testers should be aware of their causes. A false positive occurs when another substance is present in the body that has the same structure as the illegal drugs being tested. Below are some of the most common causes of false positives in drug tests.

    1. Over-the-counter medication. Cold and cough medicine which contain Phenylephrine, Ibuprofen or Ephedrine like Nyquil, Sudafed, Dimetapp and even Vicks Nasal Spray can yield a false positive result for Marijuana or Amphetamines. Likewise, Riboflavin (B2) or vitamins, diet pills with Phenylpropanolamine and asthma medication (Marax, Bronkaid, Primatine) can give false positives.

    2. Prescription medication. Most prescription medicine (Amfepramone, Cathne, Etafediabe, Morazone) or other medication such as Dexedrine or Tylenol with Codeine and anti-anxiety meds can yield false positive results for Ecstasy, Opiates, Benzodiazepine and Amphetamines.

    3. Illnesses or diseases. People with diabetes and kidney or liver infections may cause their tests to come up with false positive results for Cocaine and Ecstasy in some testing methods.

    False negatives, on the other hand, occur when results indicate the absence of drugs in the sample even if there is the presence of these in the system of the one being tested. The following are some possible causes of false negative results.

    1.  High cut-off levels. Different drug screening kits are set to various cut-off levels, the standard being those set by SAMHSA (Substance Abuse and Mental Health Services Administration) or NIDA. A high cut-off level may report a negative test result, even if there is a presence of illegal drugs in the sample.

    2. Excess water. Reports state that the intake of large amounts of water or diuretic liquid such as coffee or tea may yield alse positive results.

    3. Adulterants or additives. Some people add different substances (bleach, salt, peroxide) to their urine samples or intake various detoxifying drinks (Naturally Clean, System Flush, Urine Luck) to cheat their way through drug screening.

    Although most drug screening kits are reliable and claim accuracies of up to 98%, they aren’t bulletproof and may give incorrect results. The first step to ensure proper, reliable drug testing is in preventing false positive and false negative results by understanding what they are and how they affect drug screening results. This understanding may save your home and even your company from the damage and harm from inaccurate drug test results.


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