Monitoring of opioids and other medication prescribed patients is important to ensure safe and effective therapy. Many substances that are prescribed for pain management and other legitimate indications are found to be taken incorrectly (either inadvertently or purposefully), shared, sold, or otherwise misdirected (1). To ensure safe and effective therapy, current practice guidelines recommend monitoring patients for adherence to prescribed medications and abstinence from nonprescribed drugs through periodic drug tests (2, 3).

Urine drug testing is one of the important tool to identify patients who qualify for therapy and then to evaluate the continued effectiveness of pain relief; assess the potential for misuse, addiction or diversion; and ensure adherence to an agreed upon treatment plan. For drug testing, urine specimen is so important because of noninvasive collection, a relatively easy, cost-effective and increased window of detection (1-3 days for the most drugs or their metabolites (2, 4). Urine collection in pain management is typically unwitnessed. Since specimen substitution and adulteration do occur, it is reasonable to conduct specimen validity test such as pH, creatinine, oxidants, and specific gravity

In pain management practice, periodic urine drug testing is so important to monitor compliance with prescribed medications, in addition to identifying use of non-prescribed, and illegal drugs.

Commonly Urine Drug Testing Methods

Urine drug testing method can be screening or presumptive (usually immunoassay) and confirmatory or defintative.

Presumptive (Screening) Drug Monitoring

Presumptive (also called "Screening testing") is a qualitative technique to identify possible use or non-use of drugs or drug classes and includes lab based immunoassay and point-of-care methods. Screening tests yield rapid results, are inexpensive, and are available for a wide variety of drugs, but they are not very precise (4).

A screening result commonly indicates that a class of drugs is positive, not necessarily which specific drug triggered the positive. It is more likely give false test results due to lack of sensitivity and specificity. Screening test is also subject to cross-reactivity; i.e. substances with similar, and sometimes dissimilar, chemical composition may yield a false positive for the target drug. For this reason, specific identification of positive result (i.e. with LCMS/MS) is recommended (1).

Most common screening urine drug testing include: Amphetamine, Benzodiazepines, Barbiturates, Cocaine, Opioids, Oxycodone, Methadone and alcohol. Screening testing may not be available for some of the commonly used and potentially misused medications such as tramadol, tapentadol, and gabapentin.

Definitive (confirmatory) Drug Monitoring

Definitive drug monitoring identifies specific drugs and metabolites, and can confirm presumptive results or rule out presumptive false-positives. It is commonly performed to "confirm" positive screening results, negative screening results for expected drugs or to test for drugs that do not offer screening options. Confirmation testing uses highly specific and sensitive analytical methodology such as LC-MS (liquid chromatography–mass spectrometry). The analyser provide a molecular fingerprint of the drugs that are present in the sample and provide corresponding measured drug concentrations with detection limits much lower than screening assays. Such testing utilized to provide specific drug identification which may be qualitative or quantitative. The decision-making process of whether to order confirmation testing should include (5):

  1. Are the presumptive results inconsistent with clinical expectations or the pharmacy record?
  2. Does the presumptive test detect the drug(s) of interest?
  3. Is definitive identification of a drug required (applicable mainly to IA drug class tests)?
  4. Are quantitative results required?
  5. What illicit substances should I consider based on the patient’s history, clinical presentation, and/or community usage?

In some cases, definitive testing may be the only test option if presumptive testing is not available for a certain drug (e.g., tapentadol).

Test Result Interpretation

Testing results may be surprising not only when unexpected positive results are found, but also when expected positives are absent. Inappropriate interpretation of results may adversely affect clinical decision. Knowledge of the limitations of testing, cut-off or threshold concentrations, drug targets and cross reactivity is important. Knowledge of metabolic patterns, and the influence of pharmacokinetics is necessary for appropriate interpretation of results. Physicians should use UDT results in conjunction with or adjust the established boundaries of the treatment plan (1). A working relationship with a testing laboratory may be a very helpful in accurately interpreting urine test results. Most importantly, a physician should have a relationship of mutual honesty and trust with the patient when using UDT in his or her clinical practice.

In general, Pain management practices include presumptive testing and confirming unexpected positives or negatives with definitive testing, as well as direct-to-definitive testing when a presumptive test for a specific drug is not available. Drug testing should never be used as a punitive measure but rather to enhance patient care.

References

  1. Howard A. Heit, MD, FACP, FASAM and Douglas L. Gourlay, MD, MSc, FRCPC, FASAM. Urine Drug Testing in Pain Medicine. Journal of Pain and Symptom Management Vol. 27 No. 3 March 2004
  2. Caplan YH, Goldberger BA. Alternative specimens for workplace drug testing. J Anal Toxicology 2001:2001;25:396-399
  3. American Academy of Family Physicians. Chronic Pain Management and Opioid Misuse: A Public Health Concern (Position Paper). [ Accessed: May 2019
  4. Jannetto PJ, Bratanow NC, Clark WA, et al. Journal of Applied Laboratory Medicine. Executive Summary: American Association of Clinical Chemistry Laboratory Medicine Practice Guideline - Using Clinical Laboratory Tests to Monitor Drug Therapy in Pain Management Patients[ Accessed: Feb 2019]
  5. Louis Baxter and etal. Appropriate Use of Drug Testing in Clinical Addiction Medicine. Journal of American Society of Addiction Medicine: 2017

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