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Urine drug screens: When might a test result be false-positive?
Mr. L, age 35, has an appointment at a mental health clinic for ongoing treatment of depression. His medication list includes atorvastatin, bupropion, lisinopril, and cranberry capsules for non-descriptive urinary issues. He has been treated for some time at a different outpatient facility; however he recently moved and changed clinics.
At this visit, his first, Mr. L receives a full physical exam, including a urine drug screen point-of-care (POC) test. He informs the nurse that he has an extensive history of drug abuse: “You name it, I’ve done it.” Although he experimented with many illicit substances, he acknowledges that “downers” were his favorite. He believes that his drug abuse could have caused his depression, but is proud to declare that he has been “clean” for 12 months and his depression is approaching remission.
However, the urine drug screen is positive for amphetamines. Mr. L vehemently swears that the test must be wrong, restating that he has been clean for 12 months. “Besides, I don’t even like ‘uppers’!” Because of Mr. L’s insistence, the clinician does a brief literature search about false-positive results in urine drug screening, which shows that, rarely, bupropion can trigger a false positive in the amphetamine immunoassay.
Could this be a false-positive result? Or is Mr. L not telling the truth?
Because no clinical lab test is perfect, any clinician who runs urine drug screens will encounter a false-positive result. (See the Box,1-3 for discussion of false negatives.) Understanding how each test works—and potential sources of error— can help you evaluate test results and determine the best course of action.
There are 2 main methods involved in urine drug testing: in-office (POC) urine testing and laboratory-based testing. This article describes the differences between these tests and summarizes the potential for false-positive results.
In-office urine testing
POC tests in urine drug screens use a technique called “immunoassay,” which is quantitative and generally will detect the agent in urine for only 3 to 7 days after ingestion.4 This test relies on the principle of competitive binding: If a parent drug or metabolite is present in urine, it will bind to a specific antibody site on the test strip and produce a positive result.5 Other compounds that are similarly “shaped” on a molecular level also can bind to these antibody sites when present in sufficient quantity, producing a “cross reaction,” also called a “false-positive” result. The Table6 lists agents that can cross-react with immunoassay tests. In addition to the cross-reaction, false positives also can occur because of technician or clerical error— making it important to review the process by which the specimen was obtained and tested if a false-positive result is suspected, as in the case described here.7
Different POC tests can have varying cross-reactivity patterns, based on the antibody used.8 In general, false positives in immunoassays are rare, but amphetamine and opiate false positives are more common than cocaine metabolite and cannabinoid false positives.9 The odds of a false positive vary, depending on the specificity of the immunoassay used and the substance under detection.6
A study that analyzed 10,000 POC urine drug screens found that 362 specimens tested positive for amphetamines, but that 128 of those did not test positive for amphetamines using more sensitive tests.10 Of these 128 false positives reported, 53 patients were taking bupropion at the time of the test.10 Therefore, clinicians should do a thorough patient medication review at the time of POC urine drug testing. In addition, consider identifying which type of test you are using at your practice site, and ask the manufacturer or lab to provide a list of known possible false positives.
Laboratory-based GC–MS testing
If a false positive is suspected on a POC immunoassay-based urine drug screen, results can be confirmed using gas chromatography–mass spectrometry (GC–MS). Although GC–MS is more accurate than an immunoassay, it also is more expensive and time-consuming.9
GC–MS breaks down a specimen into ionized fragments and separates them based on their mass–charge ratio. Because of this, GC–MS is able to identify the presence of a specific drug (eg, oxycodone) instead of a broad class (eg, opioid). The GC–MS method is a good tool to confirm initial positive screens when their integrity is in question because, unlike POC tests used during an office visit, GC–MS is not influenced by cross-reacting compounds.11-13
GC–MS is not error-free, however. For example, heroin and hydrocodone are metabolized into morphine and hydromorphone, respectively. Depending on when the specimen was collected, the metabolites, not the parents, might be the compounds identified, which might produce confusing results.
Clinical recommendations
When a POC drug screen is positive, confirming the result with GC–MS is good clinical practice. False positives can strain the relationship between patient and provider, thus compromising care. Examining the procedures that were used to obtain the specimen, as well as double-checking POC test results, is, when appropriate, good medicine.
CASE CONTINUED
Because Mr. L is adamant about his sobriety and the fact that his drugs of choice were sedatives, not stimulants, the clinician orders a second drug screen by GC–MS. The second screen is negative for substances of abuse; Mr. L’s clinician concludes that bupropion produced a false-positive result on the POC urine drug screen, confirming Mr. L’s assertions.
Related Resources
• Saitman A, Park HD, Fitzgerald RL. False-positive interferences of common urine drug screen immunoassays: a review. J Anal Toxicol. 2014;38(7):387-396.
• Tenore PL. Advanced urine toxicology testing. J Addict Dis. 2010;29(4):436-448.
Drug Brand Names
Amantadine • Symadine, Symmetrel
Amitriptyline • Elavil
Atorvastatin • Lipitor
Brompheniramine • Dimetane
Bupropion • Wellbutrin, Zyban
Carbamazepine • Carbatrol, Tegretol
Chlorpromazine • Thorazine
Clomipramine • Anafranil
Cyclobenzaprine • Amrix, Flexeril
Cyproheptadine • Periactin
Desipramine • Nopramin
Desoxyephedrine • Desoxyn
Dextromethorphan • Delsym, Robitussin
Dicyclomine • Bentyl, Dicyclocot
Diphenhydramine • Benadryl, Unisom
Doxylamine • Robitussin, NyQuil
Dronabinol • Marinol
Efavirenz • Sustiva
Ephedrine • Mistol, Va-Tro-Nol
Ergotamine • Ergomar, Cafergot
Hydrocodone • Vicodin
Hydromophone • Dilaudid, Palladone
Hydroxyzine • Atarax, Vistaril
Isometheptene • Amidrine, Migrend
Isoxsuprine • Vasodilan, Vasoprine
Ketoprofen • Orudis, Oruvail
Labetalol • Normodyne, Trandate
Lisinopril • Prinivil, Zestril
Meperidine • Demerol
Naproxen • Aleve, Naprosyn
Oxaprozin • Daypro
Oxycodone • Oxycontin, Percocet, Percodan, Roxicodone
Phentermine • Adipex, Phentrol
Phenylephrine • Sudafed PE, Neo-Synephrine
Piroxicam • Feldene
Promethazine • Phenergan
Pseudoephedrine • Sudafed, Dimetapp
Quetiapine • Seroquel
Ranitidine • Zantac
Rifampin • Rifadin, Rimactane
Selegiline • EMSAM
Sertraline • Zoloft
Sulindac • Clinoril
Sumatriptan • Imitrex
Thioridazine • Mellaril
Tolmetin • Tolectin
Trazodone • Desyrel, Oleptro
Trimethobenzamide • Benzacot, Tigan
Trimipramine • Surmontil
Verapamil • Calan, Isoptin
1. Cobaugh DJ, Gainor C, Gaston CL, et al. The opioid abuse and misuse epidemic: implications for pharmacists in hospitals and health systems. Am J Health Syst Pharm. 2014;71(18):1539-1554.
2. Gilbert JW, Wheeler GR, Mick GE, et al. Importance of urine drug testing in the treatment of chronic noncancer pain: implications of recent medicare policy changes in Kentucky. Pain Physician. 2010;13(2):167-186.
3. Michna E, Jamison RN, Pham LD, et al. Urine toxicology screening among chronic pain patients on opioid therapy: frequency and predictability of abnormal findings. Clin J Pain. 2007;23(2):173-179.
4. U.S. Department of Justice. Fact sheet: drug testing in the criminal justice system. https://www.ncjrs.gov/pdffiles/dtest. pdf. Published March 1992. Accessed July 29, 2015.
5. Australian Diagnostic Services. Technical information: testing principle’s. http://www.australiandrugtesting. com/#!technical-info/c14h4. Accessed November 5, 2014.
6. University of Illinois at Chicago College of Pharmacy. What drugs are likely to interfere with urine drug screens? http://dig.pharm.uic.edu/faq/2011/Feb/faq1.aspx. Accessed November 5, 2014.
7. Wolff K, Farrell M, Marsden J, et al. A review of biological indicators of illicit drug use, practical considerations and clinical usefulness. Addiction. 1999;94(9):1279-1298.
8. Gourlay D, Heit H, Caplan YH. Urine drug testing in primary care – dispelling the myths & designing strategies. PharmaCom Group. http://www.mc.uky.edu/equip-4-pcps/documents/ section8/urine%20drug%20testing%20in%20clinical%20 practice.pdf. Accessed August 6, 2015.
9. Standridge JB, Adams SM, Zotos AP. Urine drug screen: a valuable office procedure. Am Fam Physician. 2010;81(5): 635-640.
10. Casey ER, Scott MG, Tang S, et al. Frequency of false positive amphetamine screens due to bupropion using the Syva EMIT II immunoassay. J Med Toxicol. 2011;7(2):105-108.
11. Casavant MJ. Urine drug screening in adolescents. Pediatr Clin N Am. 2002;49(2):317-327.
12. Shults TF. The medical review officer handbook. 7th ed. Chapel Hill, NC: Quadrangle Research; 1999.
13. Baden LR, Horowitz G, Jacoby H, et al. Quinolones and false-positive urine screening for opiates by immunoassay technology. JAMA. 2001;286(24):3115-3119.
Mr. L, age 35, has an appointment at a mental health clinic for ongoing treatment of depression. His medication list includes atorvastatin, bupropion, lisinopril, and cranberry capsules for non-descriptive urinary issues. He has been treated for some time at a different outpatient facility; however he recently moved and changed clinics.
At this visit, his first, Mr. L receives a full physical exam, including a urine drug screen point-of-care (POC) test. He informs the nurse that he has an extensive history of drug abuse: “You name it, I’ve done it.” Although he experimented with many illicit substances, he acknowledges that “downers” were his favorite. He believes that his drug abuse could have caused his depression, but is proud to declare that he has been “clean” for 12 months and his depression is approaching remission.
However, the urine drug screen is positive for amphetamines. Mr. L vehemently swears that the test must be wrong, restating that he has been clean for 12 months. “Besides, I don’t even like ‘uppers’!” Because of Mr. L’s insistence, the clinician does a brief literature search about false-positive results in urine drug screening, which shows that, rarely, bupropion can trigger a false positive in the amphetamine immunoassay.
Could this be a false-positive result? Or is Mr. L not telling the truth?
Because no clinical lab test is perfect, any clinician who runs urine drug screens will encounter a false-positive result. (See the Box,1-3 for discussion of false negatives.) Understanding how each test works—and potential sources of error— can help you evaluate test results and determine the best course of action.
There are 2 main methods involved in urine drug testing: in-office (POC) urine testing and laboratory-based testing. This article describes the differences between these tests and summarizes the potential for false-positive results.
In-office urine testing
POC tests in urine drug screens use a technique called “immunoassay,” which is quantitative and generally will detect the agent in urine for only 3 to 7 days after ingestion.4 This test relies on the principle of competitive binding: If a parent drug or metabolite is present in urine, it will bind to a specific antibody site on the test strip and produce a positive result.5 Other compounds that are similarly “shaped” on a molecular level also can bind to these antibody sites when present in sufficient quantity, producing a “cross reaction,” also called a “false-positive” result. The Table6 lists agents that can cross-react with immunoassay tests. In addition to the cross-reaction, false positives also can occur because of technician or clerical error— making it important to review the process by which the specimen was obtained and tested if a false-positive result is suspected, as in the case described here.7
Different POC tests can have varying cross-reactivity patterns, based on the antibody used.8 In general, false positives in immunoassays are rare, but amphetamine and opiate false positives are more common than cocaine metabolite and cannabinoid false positives.9 The odds of a false positive vary, depending on the specificity of the immunoassay used and the substance under detection.6
A study that analyzed 10,000 POC urine drug screens found that 362 specimens tested positive for amphetamines, but that 128 of those did not test positive for amphetamines using more sensitive tests.10 Of these 128 false positives reported, 53 patients were taking bupropion at the time of the test.10 Therefore, clinicians should do a thorough patient medication review at the time of POC urine drug testing. In addition, consider identifying which type of test you are using at your practice site, and ask the manufacturer or lab to provide a list of known possible false positives.
Laboratory-based GC–MS testing
If a false positive is suspected on a POC immunoassay-based urine drug screen, results can be confirmed using gas chromatography–mass spectrometry (GC–MS). Although GC–MS is more accurate than an immunoassay, it also is more expensive and time-consuming.9
GC–MS breaks down a specimen into ionized fragments and separates them based on their mass–charge ratio. Because of this, GC–MS is able to identify the presence of a specific drug (eg, oxycodone) instead of a broad class (eg, opioid). The GC–MS method is a good tool to confirm initial positive screens when their integrity is in question because, unlike POC tests used during an office visit, GC–MS is not influenced by cross-reacting compounds.11-13
GC–MS is not error-free, however. For example, heroin and hydrocodone are metabolized into morphine and hydromorphone, respectively. Depending on when the specimen was collected, the metabolites, not the parents, might be the compounds identified, which might produce confusing results.
Clinical recommendations
When a POC drug screen is positive, confirming the result with GC–MS is good clinical practice. False positives can strain the relationship between patient and provider, thus compromising care. Examining the procedures that were used to obtain the specimen, as well as double-checking POC test results, is, when appropriate, good medicine.
CASE CONTINUED
Because Mr. L is adamant about his sobriety and the fact that his drugs of choice were sedatives, not stimulants, the clinician orders a second drug screen by GC–MS. The second screen is negative for substances of abuse; Mr. L’s clinician concludes that bupropion produced a false-positive result on the POC urine drug screen, confirming Mr. L’s assertions.
Related Resources
• Saitman A, Park HD, Fitzgerald RL. False-positive interferences of common urine drug screen immunoassays: a review. J Anal Toxicol. 2014;38(7):387-396.
• Tenore PL. Advanced urine toxicology testing. J Addict Dis. 2010;29(4):436-448.
Drug Brand Names
Amantadine • Symadine, Symmetrel
Amitriptyline • Elavil
Atorvastatin • Lipitor
Brompheniramine • Dimetane
Bupropion • Wellbutrin, Zyban
Carbamazepine • Carbatrol, Tegretol
Chlorpromazine • Thorazine
Clomipramine • Anafranil
Cyclobenzaprine • Amrix, Flexeril
Cyproheptadine • Periactin
Desipramine • Nopramin
Desoxyephedrine • Desoxyn
Dextromethorphan • Delsym, Robitussin
Dicyclomine • Bentyl, Dicyclocot
Diphenhydramine • Benadryl, Unisom
Doxylamine • Robitussin, NyQuil
Dronabinol • Marinol
Efavirenz • Sustiva
Ephedrine • Mistol, Va-Tro-Nol
Ergotamine • Ergomar, Cafergot
Hydrocodone • Vicodin
Hydromophone • Dilaudid, Palladone
Hydroxyzine • Atarax, Vistaril
Isometheptene • Amidrine, Migrend
Isoxsuprine • Vasodilan, Vasoprine
Ketoprofen • Orudis, Oruvail
Labetalol • Normodyne, Trandate
Lisinopril • Prinivil, Zestril
Meperidine • Demerol
Naproxen • Aleve, Naprosyn
Oxaprozin • Daypro
Oxycodone • Oxycontin, Percocet, Percodan, Roxicodone
Phentermine • Adipex, Phentrol
Phenylephrine • Sudafed PE, Neo-Synephrine
Piroxicam • Feldene
Promethazine • Phenergan
Pseudoephedrine • Sudafed, Dimetapp
Quetiapine • Seroquel
Ranitidine • Zantac
Rifampin • Rifadin, Rimactane
Selegiline • EMSAM
Sertraline • Zoloft
Sulindac • Clinoril
Sumatriptan • Imitrex
Thioridazine • Mellaril
Tolmetin • Tolectin
Trazodone • Desyrel, Oleptro
Trimethobenzamide • Benzacot, Tigan
Trimipramine • Surmontil
Verapamil • Calan, Isoptin
Mr. L, age 35, has an appointment at a mental health clinic for ongoing treatment of depression. His medication list includes atorvastatin, bupropion, lisinopril, and cranberry capsules for non-descriptive urinary issues. He has been treated for some time at a different outpatient facility; however he recently moved and changed clinics.
At this visit, his first, Mr. L receives a full physical exam, including a urine drug screen point-of-care (POC) test. He informs the nurse that he has an extensive history of drug abuse: “You name it, I’ve done it.” Although he experimented with many illicit substances, he acknowledges that “downers” were his favorite. He believes that his drug abuse could have caused his depression, but is proud to declare that he has been “clean” for 12 months and his depression is approaching remission.
However, the urine drug screen is positive for amphetamines. Mr. L vehemently swears that the test must be wrong, restating that he has been clean for 12 months. “Besides, I don’t even like ‘uppers’!” Because of Mr. L’s insistence, the clinician does a brief literature search about false-positive results in urine drug screening, which shows that, rarely, bupropion can trigger a false positive in the amphetamine immunoassay.
Could this be a false-positive result? Or is Mr. L not telling the truth?
Because no clinical lab test is perfect, any clinician who runs urine drug screens will encounter a false-positive result. (See the Box,1-3 for discussion of false negatives.) Understanding how each test works—and potential sources of error— can help you evaluate test results and determine the best course of action.
There are 2 main methods involved in urine drug testing: in-office (POC) urine testing and laboratory-based testing. This article describes the differences between these tests and summarizes the potential for false-positive results.
In-office urine testing
POC tests in urine drug screens use a technique called “immunoassay,” which is quantitative and generally will detect the agent in urine for only 3 to 7 days after ingestion.4 This test relies on the principle of competitive binding: If a parent drug or metabolite is present in urine, it will bind to a specific antibody site on the test strip and produce a positive result.5 Other compounds that are similarly “shaped” on a molecular level also can bind to these antibody sites when present in sufficient quantity, producing a “cross reaction,” also called a “false-positive” result. The Table6 lists agents that can cross-react with immunoassay tests. In addition to the cross-reaction, false positives also can occur because of technician or clerical error— making it important to review the process by which the specimen was obtained and tested if a false-positive result is suspected, as in the case described here.7
Different POC tests can have varying cross-reactivity patterns, based on the antibody used.8 In general, false positives in immunoassays are rare, but amphetamine and opiate false positives are more common than cocaine metabolite and cannabinoid false positives.9 The odds of a false positive vary, depending on the specificity of the immunoassay used and the substance under detection.6
A study that analyzed 10,000 POC urine drug screens found that 362 specimens tested positive for amphetamines, but that 128 of those did not test positive for amphetamines using more sensitive tests.10 Of these 128 false positives reported, 53 patients were taking bupropion at the time of the test.10 Therefore, clinicians should do a thorough patient medication review at the time of POC urine drug testing. In addition, consider identifying which type of test you are using at your practice site, and ask the manufacturer or lab to provide a list of known possible false positives.
Laboratory-based GC–MS testing
If a false positive is suspected on a POC immunoassay-based urine drug screen, results can be confirmed using gas chromatography–mass spectrometry (GC–MS). Although GC–MS is more accurate than an immunoassay, it also is more expensive and time-consuming.9
GC–MS breaks down a specimen into ionized fragments and separates them based on their mass–charge ratio. Because of this, GC–MS is able to identify the presence of a specific drug (eg, oxycodone) instead of a broad class (eg, opioid). The GC–MS method is a good tool to confirm initial positive screens when their integrity is in question because, unlike POC tests used during an office visit, GC–MS is not influenced by cross-reacting compounds.11-13
GC–MS is not error-free, however. For example, heroin and hydrocodone are metabolized into morphine and hydromorphone, respectively. Depending on when the specimen was collected, the metabolites, not the parents, might be the compounds identified, which might produce confusing results.
Clinical recommendations
When a POC drug screen is positive, confirming the result with GC–MS is good clinical practice. False positives can strain the relationship between patient and provider, thus compromising care. Examining the procedures that were used to obtain the specimen, as well as double-checking POC test results, is, when appropriate, good medicine.
CASE CONTINUED
Because Mr. L is adamant about his sobriety and the fact that his drugs of choice were sedatives, not stimulants, the clinician orders a second drug screen by GC–MS. The second screen is negative for substances of abuse; Mr. L’s clinician concludes that bupropion produced a false-positive result on the POC urine drug screen, confirming Mr. L’s assertions.
Related Resources
• Saitman A, Park HD, Fitzgerald RL. False-positive interferences of common urine drug screen immunoassays: a review. J Anal Toxicol. 2014;38(7):387-396.
• Tenore PL. Advanced urine toxicology testing. J Addict Dis. 2010;29(4):436-448.
Drug Brand Names
Amantadine • Symadine, Symmetrel
Amitriptyline • Elavil
Atorvastatin • Lipitor
Brompheniramine • Dimetane
Bupropion • Wellbutrin, Zyban
Carbamazepine • Carbatrol, Tegretol
Chlorpromazine • Thorazine
Clomipramine • Anafranil
Cyclobenzaprine • Amrix, Flexeril
Cyproheptadine • Periactin
Desipramine • Nopramin
Desoxyephedrine • Desoxyn
Dextromethorphan • Delsym, Robitussin
Dicyclomine • Bentyl, Dicyclocot
Diphenhydramine • Benadryl, Unisom
Doxylamine • Robitussin, NyQuil
Dronabinol • Marinol
Efavirenz • Sustiva
Ephedrine • Mistol, Va-Tro-Nol
Ergotamine • Ergomar, Cafergot
Hydrocodone • Vicodin
Hydromophone • Dilaudid, Palladone
Hydroxyzine • Atarax, Vistaril
Isometheptene • Amidrine, Migrend
Isoxsuprine • Vasodilan, Vasoprine
Ketoprofen • Orudis, Oruvail
Labetalol • Normodyne, Trandate
Lisinopril • Prinivil, Zestril
Meperidine • Demerol
Naproxen • Aleve, Naprosyn
Oxaprozin • Daypro
Oxycodone • Oxycontin, Percocet, Percodan, Roxicodone
Phentermine • Adipex, Phentrol
Phenylephrine • Sudafed PE, Neo-Synephrine
Piroxicam • Feldene
Promethazine • Phenergan
Pseudoephedrine • Sudafed, Dimetapp
Quetiapine • Seroquel
Ranitidine • Zantac
Rifampin • Rifadin, Rimactane
Selegiline • EMSAM
Sertraline • Zoloft
Sulindac • Clinoril
Sumatriptan • Imitrex
Thioridazine • Mellaril
Tolmetin • Tolectin
Trazodone • Desyrel, Oleptro
Trimethobenzamide • Benzacot, Tigan
Trimipramine • Surmontil
Verapamil • Calan, Isoptin
1. Cobaugh DJ, Gainor C, Gaston CL, et al. The opioid abuse and misuse epidemic: implications for pharmacists in hospitals and health systems. Am J Health Syst Pharm. 2014;71(18):1539-1554.
2. Gilbert JW, Wheeler GR, Mick GE, et al. Importance of urine drug testing in the treatment of chronic noncancer pain: implications of recent medicare policy changes in Kentucky. Pain Physician. 2010;13(2):167-186.
3. Michna E, Jamison RN, Pham LD, et al. Urine toxicology screening among chronic pain patients on opioid therapy: frequency and predictability of abnormal findings. Clin J Pain. 2007;23(2):173-179.
4. U.S. Department of Justice. Fact sheet: drug testing in the criminal justice system. https://www.ncjrs.gov/pdffiles/dtest. pdf. Published March 1992. Accessed July 29, 2015.
5. Australian Diagnostic Services. Technical information: testing principle’s. http://www.australiandrugtesting. com/#!technical-info/c14h4. Accessed November 5, 2014.
6. University of Illinois at Chicago College of Pharmacy. What drugs are likely to interfere with urine drug screens? http://dig.pharm.uic.edu/faq/2011/Feb/faq1.aspx. Accessed November 5, 2014.
7. Wolff K, Farrell M, Marsden J, et al. A review of biological indicators of illicit drug use, practical considerations and clinical usefulness. Addiction. 1999;94(9):1279-1298.
8. Gourlay D, Heit H, Caplan YH. Urine drug testing in primary care – dispelling the myths & designing strategies. PharmaCom Group. http://www.mc.uky.edu/equip-4-pcps/documents/ section8/urine%20drug%20testing%20in%20clinical%20 practice.pdf. Accessed August 6, 2015.
9. Standridge JB, Adams SM, Zotos AP. Urine drug screen: a valuable office procedure. Am Fam Physician. 2010;81(5): 635-640.
10. Casey ER, Scott MG, Tang S, et al. Frequency of false positive amphetamine screens due to bupropion using the Syva EMIT II immunoassay. J Med Toxicol. 2011;7(2):105-108.
11. Casavant MJ. Urine drug screening in adolescents. Pediatr Clin N Am. 2002;49(2):317-327.
12. Shults TF. The medical review officer handbook. 7th ed. Chapel Hill, NC: Quadrangle Research; 1999.
13. Baden LR, Horowitz G, Jacoby H, et al. Quinolones and false-positive urine screening for opiates by immunoassay technology. JAMA. 2001;286(24):3115-3119.
1. Cobaugh DJ, Gainor C, Gaston CL, et al. The opioid abuse and misuse epidemic: implications for pharmacists in hospitals and health systems. Am J Health Syst Pharm. 2014;71(18):1539-1554.
2. Gilbert JW, Wheeler GR, Mick GE, et al. Importance of urine drug testing in the treatment of chronic noncancer pain: implications of recent medicare policy changes in Kentucky. Pain Physician. 2010;13(2):167-186.
3. Michna E, Jamison RN, Pham LD, et al. Urine toxicology screening among chronic pain patients on opioid therapy: frequency and predictability of abnormal findings. Clin J Pain. 2007;23(2):173-179.
4. U.S. Department of Justice. Fact sheet: drug testing in the criminal justice system. https://www.ncjrs.gov/pdffiles/dtest. pdf. Published March 1992. Accessed July 29, 2015.
5. Australian Diagnostic Services. Technical information: testing principle’s. http://www.australiandrugtesting. com/#!technical-info/c14h4. Accessed November 5, 2014.
6. University of Illinois at Chicago College of Pharmacy. What drugs are likely to interfere with urine drug screens? http://dig.pharm.uic.edu/faq/2011/Feb/faq1.aspx. Accessed November 5, 2014.
7. Wolff K, Farrell M, Marsden J, et al. A review of biological indicators of illicit drug use, practical considerations and clinical usefulness. Addiction. 1999;94(9):1279-1298.
8. Gourlay D, Heit H, Caplan YH. Urine drug testing in primary care – dispelling the myths & designing strategies. PharmaCom Group. http://www.mc.uky.edu/equip-4-pcps/documents/ section8/urine%20drug%20testing%20in%20clinical%20 practice.pdf. Accessed August 6, 2015.
9. Standridge JB, Adams SM, Zotos AP. Urine drug screen: a valuable office procedure. Am Fam Physician. 2010;81(5): 635-640.
10. Casey ER, Scott MG, Tang S, et al. Frequency of false positive amphetamine screens due to bupropion using the Syva EMIT II immunoassay. J Med Toxicol. 2011;7(2):105-108.
11. Casavant MJ. Urine drug screening in adolescents. Pediatr Clin N Am. 2002;49(2):317-327.
12. Shults TF. The medical review officer handbook. 7th ed. Chapel Hill, NC: Quadrangle Research; 1999.
13. Baden LR, Horowitz G, Jacoby H, et al. Quinolones and false-positive urine screening for opiates by immunoassay technology. JAMA. 2001;286(24):3115-3119.
