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Last updated on June 27, Have you been asked to take a drug test? Maybe this caught you off guard. Screening drug tests are often required for pre-employment in the private and government sector, for athletes, students, healthcare workers, for probation or criminal activity, for opioid avoidance testing in the clinic, or after vehicle or workplace accidents.
Even though these tests are common, people often have questions about the possibility of false-positive. Anyone subject to a drug screen should confirm that secondary confirmatory testing such as gas chromatography—mass spectrometry [GC-MS] or high performance liquid chromatography is performed on any positive result received by the lab doing your testing. Drug tests are typically done on urine, but other types of specimens are also used, such as hair, saliva or blood.
The most commonly screened substances, and also required by Federal workplace guidelines, include these five of drugs:. Drug screening can negatively affect many circumstances; therefore, accuracy is of the utmost importance. A worry for anyone undergoing an illicit drug screen - whether it be a urine, hair, saliva or blood test - is the possibility of a false positive drug test. In fact, data suggests 5 to 10 percent of all drug tests may result in false positives and 10 to 15 percent may yield false negatives.
The increased use of onsite, workplace random drug testing and home-testing kits emphasize the need for reliable, confirmatory testing. Negative consequences of false-positive drug testing can include 1 :. When initial screening drugs tests called immunoassays result in positivea second confirmatory Gas Chromatography Mass Spectrometry or GC-MS test - which should always be done on positive - greatly lessens the chance of a false positive, almost reducing the False drug test readings to zero. The initial immunoassay allows quick, large scale screenings with minimal cost. When urine or other specimens are collected, they are split into two samples, and one portion should be saved for confirmatory testing.
For instances where an initial drug screen returns a positive result, the GC-MS test is run on this additional saved portion to confirm or deny. Rarely, a drug test may report the presence of illicit or prescription drugs in the immunoassay, although the person has not used these drugs. It is important that if you are undergoing drug testing, that you give a complete and accurate history of all prescription drugs, over-the-counter OTC medications, and vitamin, dietary supplement, and herbal products used prior to the time of the sample collection. The of your drug testing should remain confidential and kept separate from the regular employee work file.
False-positive drug test have been reported in multiple drug classes. Some of the more common classes include cold and allergy products, pain medications, and drugs for infections:. The chart below identifies common substances reported to cause a false-positive result based on the initial immunoassay testing. Remember, any positive drug test should always be confirmed with a secondary test such as GC-MS that detects and provides identification and levels of a specific compound.
Poppy seedsoften found on bagels, rolls, and pastries have long been used as a defense against positive opiate test encountered on a urine drug screen. It is known that poppy seeds do contain opiates - specifically morphine and codeine; however, content varies greatly depending upon seed source and processing. Food processing may lower the opiate levels in poppy seeds. In a study published in the Journal of Analytical Toxicology10 researchers determined opiate concentrations in opiate-free volunteers from 15 minutes to 20 hours after consumption of raw poppy seeds 15 grams and prepared poppy seeds on a roll.
At 20 hours, no morphine was detected for rolls or raw seeds in urine testing. This level is current as of Over-the-counter cough and cold products such as the cough suppressant dextromethorphan have been reported to lead to a false positive result for phencyclidine PCP and possibly opiates. Dextromethorphan is chemically related to levorphanol, a narcotic analgesic. The body metabolizes codeine to morphine and both substances may be found upon testing.
Confirmatory testing can distinguish between the products. Efavirenz does not bind to cannabinoid receptors. False-positive with other cannabinoid assays have not been observed. False-positive tests for benzodiazepines have also been reported and are likely due to the 8-hydroxy-efavirenz major metabolite. NSAIDs, such as ibuprofenhave often been implicated in causing false positives but most specimens are corrected with an alternate screening methodology if this is of concern.
In one report, authors concluded that acute or chronic use of ibuprofen or chronic use of naproxen were not regularly associated with false-positives but they do recommend secondary testing if needed. Nasky and colleagues 12 reviewed positive for drug screens for benzodiazepines while taking sertraline but negative with GC-MS. They found 26 of 98 records to be identified as false positives.
Procaine brane name: Novocain or lidocaine use as a defense for cocaine abuse is not a valid excuse. If benzoylecgonine, the main metabolite of cocaine is detected in a drug test, the subject cannot claim that the result is a false positive due to Novocain administration, or any other "-caine" drug. Benzoylecgonine is only found in nature as a metabolite of cocaine, and there would be no other valid reason for its presence in a drug screen. While it is difficult to tamper with a specimen, attempts have been made False drug test readings alter samples, most often urine.
Abnormalities in the urine screen may indicate that may be a false negative or that there was deliberate adulteration of the sample. A low creatinine lab value can indicate that a urine sample was tampered with - either the subject diluted their urine by consuming excessive water just prior to testing, or water was added to the urine sample. Creatinine levels are often used in conjunction with specific gravity to determine if samples have been diluted. To help avoid this problem, the testing lab may color the water in their toilet to prevent the sample from being diluted with toilet water.
The temperature of urine is also measured, to help prevent use of a substituted urine sample brought in from the outside. Those attempting to foil the drug False drug test readings process may try to add certain enzymes to the urine sample to affect stability, but this often changes the pH, which is also tested. The most common adulterants used include certain oxidizing agents — such as False drug test readings, glutaraldehyde, chromates and halogens like bleach and iodine.
There have also been reports of people using products such as Visine eye drops to adulterate urine samples to cause a false-negative result for THC from marijuana. Ingredients in Visine, such as the preservative benzalkonium chloride or the borate buffer may decrease the concentration of 9-carboxy-THC in the initial urine immunoassay; however, upon confirmatory testing with GC-MS this metabolite will still be detected.
Testing for adulterants in addition to drugs may be requested by the person requiring the drug screen. To others who may have questions, concerns or want to voice opinions about illicit and prescription drug testing, false positives, false negatives, and other related issues, visit:.
Always consult your healthcare provider to ensure the information displayed on this applies to your personal circumstances. Negative consequences of false-positive drug testing can include 1 : loss of employment jail time exclusion from competitive sports loss of privileges in a probation setting inappropriate medical care. How are drug tests done? Some of the more common classes include cold and allergy products, pain medications, and drugs for infections: Antihistamines Antidepressants Antibiotics Analgesics Antipsychotics Decongestants Certain over-the-counter OTC drugs The chart below identifies common substances reported to cause a false-positive result based on the initial immunoassay testing.
Mayo Clin Proc. Drug Testing in the Workplace: What the pharmacist should know. Drug Topics Modern Medicine ; Oliff H. May Commonly prescribed medications and potential false-positive urine drug screens. Am J Health-Syst Pharm. Cody, J. Metabolic Precursors to Amphetamine and Methamphetamine. Forensic Science Review 2 — Quest Diagnostics. Challenging the Poppy Seed Defense. White Paper. False-positive urine screening for benzodiazepines: an association with sertraline? A two-year retrospective chart analysis. Accessed June 29, US Pharm. Subscribe to our newsletters.
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Positive Drug Test List of Causes: Medications and Food