By Anna Jankowska LCPC
Types of Drug Testing
Drug testing is becoming increasingly common during the job application process, as part of random workplace drug testing, and as a condition of probation. Individuals who have not used illicit substances occasionally find themselves subjected to positive drug tests.
Blood, hair, urine, or saliva testing may be requested. Drug testing looks for alcohol as well as certain prescription medications and illegal substances. Amphetamines, barbiturates, benzodiazepines (such as Xanax and Valium), cocaine, designer drugs (bath salts, MDMA, etc.), marijuana, opioids (narcotics including heroin or prescription opiates such as codeine), and PCP (phencyclidine) can all be detected by drug testing.
A common type of drug test is called an immunoassay test. If this test produces a positive result, the laboratory may follow up with a GC-MS (gas chromatography-mass spectrometry) test, which greatly reduces the chances of a false positive.
Can a Drug Test Lead to a False Positive?
False positives on urine drug screenings are uncommon, but no testing method is 100% reliable, and false positives do happen. Some common causes of false positives include:
• Antidepressants. Sertraline (Zoloft) can cause a false positive reading for benzodiazepine. Bupropion (Wellbutrin) can cause a false positive for amphetamines.
• Cold medicines. Non-prescription or over-the-counter cold, flu, and allergy medications that contain the ingredient pseudoephedrine can cause a drug test to show up as positive for amphetamines.
• Ibuprofen. This over-the-counter pain reliever can cause a drug test to show up as positive for barbiturates, benzodiazepines, and marijuana. 12000 mg of ibuprofen, it is thought, may interfere with the enzyme used in the testing method. Ibuprofen is in a class of pain relievers called NSAIDs (non-steroidal anti-inflammatory drugs). All NSAIDs can cause a false positive. Alternatives to ibuprofen such as aspirin and acetaminophen don’t cause the same effect and are safe to use before a drug screen.
• Poppy seed bagels. This one is so well-known it has even made its way into sitcoms, but just in case you missed it, poppy seeds contain trace amounts of opiates. Eating foods containing poppy seeds have been shown to give false positive drug tests for opiates as much as 16 hours after the seeds were ingested.
• Snack bars. A few brands of granola and snack bars contain hemp seeds for extra protein, which contain very tiny trace amounts of a chemical found in marijuana. Although you won’t get high from eating snack bars, the hemp seeds may cause a false positive drug test for marijuana. You would probably have to ingest a fairly large amount of hemp seeds to get a false positive, but just to be on the safe side, avoid these snack bars before testing.
• Tonic water. Originally developed as a medicine to fight malaria, tonic water contains the substance quinine. Quinine is made from the bark of the cinchona tree, and the bark contains substances that may cause a false positive test for opiates. The amount of tonic water used to make a mixed drink, such as a gin and tonic, is enough to cause a false positive test opiate test.
• Vitamin B supplements. The B vitamin riboflavin, or B2, is sometimes synthesized from hemp oil. Like hemp seeds, hemp oil contains tiny trace amounts of the chemical found in marijuana and is likewise capable of causing a false positive.
Drug Testing Myths
• Passive marijuana smoke can cause a false positive. This is not a valid reason for a false positive; the amount of marijuana compounds the body ingests from passively breathing marijuana smoke is well below the cut-off level detected by the drug screenings.
• Novocaine can cause a false positive for cocaine. This is also not a valid reason for a false positive, since the compounds detected by the test for cocaine are only found in cocaine and not in Novocaine. The “caine” in the two names doesn’t mean the two are chemically similar.