Ordering and Interpreting Urine Drug Tests

Two Tests: What to Order? False positives. Are the results due to illicit use, a false positive on the screen, or a known metabolite of a Two tests are available, the enzyme linked immunoassay prescribed medication? In considering prescribed (EIA) kit and gas chromatography/mass spectrometry medications, false positives on EIA (and GCMS where (GCMS). They provide different information. specified) may result from: • Illicit drugs: EIA • Amphetamines/methamphetamine: bupropion, tricyclic • Confirm taking prescribed meds (specify meds when antidepressants, phenothiazines, propranolol, labetalol, order test): GCMS. (EIA will provide this information OTC cold rx, ranitidine, trazodone. Vicks Nasal Spray if your laboratory runs the test for each med. However, can test positive even on GCMS. laboratories usually do not. Ask!) • Barbiturates: phenytoin • Use of non-prescribed medication: GCMS • Benzodiazepines: sertraline • Testing for heroin: GCMS. Check for one of its specific • LSD: amitriptyline, doxepin, sertraline, fluoxetine, metabolites, e.g., 6 monoacetyl morphine (6-AM) metoclopramide, haloperidol, risperidone, verapamil duration 2-4 hrs only is positive as morphine in 2-3 days • Opiates - EIA testing: quinolones, dextromethorphan, Enzyme linked immunoassay – EIA. diphenhydramine (Benadryl), verapamil, poppy • Screening test for illicit substances amphetamine/ seeds methamphetamine, marijuana, PCP, cocaine, “opiates” - GCMS testing (e.g., morphine/codeine) Morphine: from codeine, heroin (for a few hours) • Inexpensive, fast, point of care or lab and poppy seeds for 48 hrs • Detects class of substance, not specific medication Hydromorphone: from morphine, codeine, hydrocodone, heroin • Will be negative for hydrocodone, hydromorphone, Oxycodone: from hydrocodone oxycodone, methadone, buprenorphine, Codeine: from hydrocodone benzodiazepines (particularly clonazepam) unless Fentanyl: from trazodone specific test kit for those meds is in use. Ask your lab! Methadone: from quetiapine (Seroquel) • High false positive rates caused by numerous prescribed • PCP: dextromethorphan, diphenhydramine, NyQuil, or OTC meds tramadol, venlafaxine (Effexor), NSAIDs, imipramine

Gas chromatography/mass spectrometry – GCMS. You • Propoxyphene: methadone, cyclobenzaprine (Flexeril), must tell the laboratory the drugs you are seeking (patient is doxylamine (Ny-Quil), diphenhydramine (Benadryl), taking). imipramine • More expensive, labor intensive • Cannabinoids (on EIA not GCMS): pantoprazole (Protonix), efavirenz (Sustiva, Atripla), NSAIDs • Confirming test identifies specific meds and their

metabolites. Use to confirm patient is taking prescribed False negatives. Are the results due to the patient running meds and not taking non-prescribed meds out of medication early, diversion, a tampered specimen, or • High sensitivity a threshold issue (e.g., workplace testing using a high • False positives still occur threshold for reporting a positive test to avoid false positives that require a job intervention)? For EIA (and Results and Possible Causes GCMS where specified) false negatives may result from: • Unless bundled (ask your lab!), opiate immunoassays will Results may be due to several possible causes. miss fentanyl, meperidine, methadone, pentazocine • Illicit substance present: Use by patient; false result (Talwin), oxycodone and often hydrocodone related to prescribed or OTC med exposure • Morphine: GCMS may miss it unless glucuronide • Non-prescribed medication present: Illicit use by patient; hydrolyzed. Can pick up with a specific test such as a false positive testing – cross-reaction or possible known specific qualitative EIA kit such as MSOPIATE. (Ask metabolite (morphine or codeine may → your lab!) hydromorphone) • Illnesses that cause lactic acidosis can cause false • Prescribed medication absent: diversion or binging and negatives running out early; false negative (incorrect use of EIA • Insensitivity of benzodiazepine screen: only 40% for rather than GCMS testing); urine adulterated lorazepam; clonazepam (Klonopin) frequently negative on both EIA and GCMS.