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Are You Missing Something? Urine Drug Testing in Pain Management

by
Brooke Mueller
| Feb 03, 2016

​As previously published in Painview Vol. 12/No. 1-Winter 2016

Introduction

Clinical drug testing can be a very useful tool in assessing a patient’s adherence to their medication regimen by confirming the presence of prescribed medications and/or detecting the presence of unauthorized substances. However, studies suggest a knowledge gap in providers’ abilities to accurately interpret drug test results, and the consequences of misinterpretation are potentially serious. Misinterpretation may lead the clinician to a false sense of assurance that there is appropriate use of the prescribed medication, particularly opioid analgesics, and that substance misuse does not exist. It can also have negative consequences for the claimant, secondary to false accusations of misuse, including:

  • Loss of access to opioid analgesic therapy
  • Damage to the provider-patient relationship
  • Painful and possibly dangerous opioid analgesic withdrawal
  • Difficulty receiving appropriate therapy from future providers

Therefore, full knowledge of the capabilities and limitations of drug testing and monitoring is necessary to utilize this vital tool to its full potential. The following cases demonstrate potential nuances in the interpretation of urine drug test results that could affect the plan for the patient.

Case 1: Dave

Dave is a 57-year-old man with chronic low back pain, including a neuropathic component. He was prescribed OxyContin® 60 mg CR and duloxetine 30 mg to treat his pain. As part of his provider’s policy to randomly urine drug test any patient on chronic opioid therapy, Dave was asked to provide a urine sample during his last office visit. The sample was sent to the lab for confirmatory testing (Table 1).

Table 1: Dave


Dave_Table

Which of the results, if any, are inconsistent with Dave’s medication therapy?

At first glance, the only concern might be the absence of duloxetine. Depending on the laboratory, the oxycodone result might not be flagged as inconsistent due to the presence of the parent medication. However, the absence of the metabolites, noroxycodone and oxymorphone, might warrant further investigation. Possible reasons for detecting a parent drug in the absence of its metabolites might be due to the patient’s individual metabolism or their taking the medications just prior to urine collection.

Because of the unusual results, the lab’s toxicologist was consulted for more insight. The toxicologist agreed that the results were not typical and suggested the specimen validity tests (SVT) be reviewed. Unfortunately, SVT had not been included with the original order; however, the toxicologist was able to add an order for this panel on the sample that had not yet been discarded.

The SVT measures certain urinary characteristics, such as creatinine, pH, and specific gravity, as well as detecting the presence of oxidants in the urine.1 This is one of the most effective ways to detect adulteration or dilution, a well-known problem with urine drug testing, where a urine specimen is tampered with to intentionally alter the testing results. The revised report, including the SVT, was generated (Table 2).

Table 2: Dave

 Dave_Table2

These SVT results show a specific gravity equivalent to water, as well as abnormal creatinine. With this information, in addition to the confirmed lack of duloxetine, “pill scraping” should be considered. Pill scraping is where patients scrape a portion of their pill(s) into the urine sample in an effort to appear compliant with their current treatment regimen. This will lead to a type of false-positive on the point-of-service test; however, quantitative testing can identify the specific opioid analgesics and confirm metabolites, which will indicate if the medications were actually ingested or just scraped or shaved into the sample.2

Specimen substitution and pill shaving were discussed with Dave. Because an opioid treatment agreement was not in place between the provider and the patient, Dave was given a second chance. The results from the random urine drug test performed the following quarter are in Table 3.

Table 3: Dave

 Dave_Table3

Are there any concerns with Dave’s most recent urine drug test results?

While duloxetine is still missing from the urine, one of oxycodone’s metabolites is now present. In addition, while the specimen validity results do not indicate the sample was water, it does appear the sample has been tampered with.

A call to the laboratory toxicologist for more information about the SVT results revealed the ratio between noroxycodone and oxycodone was not consistent with what is typically seen. The ratio indicated Dave provided a small urine sample, which allowed for detection of the metabolite. In addition, the creatinine, pH, and specific gravity suggested the sample was diluted with an acidic diluent and, again, a portion of the oxycodone tablet was scraped into the specimen in an attempt to produce a consistent test result. This attempt at deception indicated the patient was trying to hide the presence of a nonprescribed and/or illicit substance or trying to cover up nonadherence with the prescribed medication.

Case 2: Jennifer

Jennifer is a 43-year-old woman who experienced a work-related crush injury in February 2007. As part of her treatment, Jennifer was prescribed hydromorphone 8 mg and methadone 10 mg for pain. Following the pain practitioner’s policy to urine drug test everyone on chronic opioid therapy, Jennifer was asked to submit a urine sample. The results are displayed in Table 4.

Table 4: Jennifer

Jennifer_Table1

When questioned on the positive THC result, the patient claims it was secondary to incidental exposure from a going away party she attended the week before urine collection.

Is this explanation a possibility?

A study conducted by Cone et al examined the effect of marijuana smoke exposure on drug free participants. The urine of nonsmoking participants were analyzed by GC-MS (gas chromatography mass spectrometry). Maximum concentrations by GC-MS for nonsmokers ranged from 1.3 to 57.5 ng/mL, but room ventilation substantially reduced exposure levels. These results demonstrate that extreme cannabis smoke exposure can produce positive urine tests at commonly utilized cutoff concentrations. However, positive tests are likely to be rare, limited to the hours immediately postexposure, and occur only under environmental circumstances where exposure is obvious, such as hot-boxing.3 Hot-boxing is the act of smoking marijuana, or another drug, in an enclosed area to which no outside air can enter. This practice maximizes the effect of the marijuana through both first and second hand smoke. When a patient claims incidental exposure as the cause of a positive THC result, the deliberate act of hot-boxing should be considered.

Case 3: Rick

Rick is a 61-year-old man with chronic shoulder pain. As part of his treatment, he was prescribed oxycodone IR 10 mg and oxycodone ER 80 mg for pain. Following the random drug testing policy of the pain practice, Rick provided a urine sample during his most recent office visit. The results of the in-office immunoassay (IA) test are in Table 5.

Table 5: Rick

 Rick_Table

Do these results warrant further investigation?

Immunoassay test results have been reported to return up to 50% false results, depending on the drug class.Immunoassay screens in general are quite susceptible to cross react with other drugs and produce false-positive results. In addition, results falling below cut-off levels will produce false-negative results.5,6 Most IA screens for opiates are primarily targeted to detecting morphine, hydrocodone, codeine, 6-acetylmorphine (metabolite of heroin), and hydromorphone.7 Because they are typically not sensitive enough to detect oxycodone, the oxycodone assay is utilized to detect oxycodone and oxymorphone.

Due to these issues, there is debate regarding when to send screening test results for confirmation. Some experts state that each and every result should be sent for confirmation, while others argue that only disputed results should be submitted.8 In Rick’s case, it was office policy to submit any positive results for confirmation. The laboratory confirmatory results are in Table 6.

Table 6: Rick

 Rick_Table2

Is the hydrocodone result inconsistent with Rick’s current pain medication regimen?

While Rick was not prescribed a hydrocodone product, hydrocodone is a known impurity of oxycodone products.6 The manufacturing of opioid analgesics may produce process impurities. These impurities may contribute to unexpected or false-positive results, even utilizing liquid or gas chromatography coupled with mass spectrometry. Allowable limits have been established for these impurities by the industry. In order to appropriately evaluate a drug test, the reader must be aware of positive results caused by medication impurities.

After further evaluation, it was determined the ratio of hydrocodone to oxycodone in the urine sample falls within the expected range for this impurity ratio; however, illicit hydrocodone use should not be completely ruled out.

Summary

Urine drug monitoring can be a very useful tool to assess patient compliance by confirming the presence of prescribed medications and detecting the presence of unauthorized substances. However, to fully take advantage of the value, providers should ensure results are accurately interpreted. As these cases show, it is important to examine the full clinical picture and consider all possible reasons for each result, expected or unexpected. When in doubt, the laboratory’s toxicologist and/or a clinical pharmacist should be consulted to clarify the results.

References:

  1. Webster LR. The role of urine drug testing in chronic pain management: 2013 Update. Pain Med News. 2013;December:45-50.
  2. Kaye AD, Marshall ZJ, Lampert SM, et al. Ethical perspectives on urine drug screening for pain physicians. Pain Physician. 2014;(17):E559-E564.
  3. Cone EJ, Bigelow GE, Herrmann ES, et al. Non-smoker exposure to secondhand cannabis smoke. I. Urine screening and confirmation results. J Anal Toxicol. 2015;39(1):1-12.
  4. Manchikanti L, Abdi S, Atluri S, et al. American Society of Interventional Pain Physicians (ASIPP) guidelines for responsible opioid prescribing in chronic non-cancer pain: Part 2–guidance. Pain Physician. 2012;15(3 suppl):S67-S116.
  5. Official Disability Guidelines (ODG). Treatment in Workers' Comp 2013 on the Web. Work Loss Data Institute. Updated October 9, 2015. Available at: www.odg-twc.com.
  6. Pesce A, West C, Egan City K, et al. Interpretation of urine drug testing in pain patients. Pain Med. 2012;13(7):868-885.
  7. Reisfield GM, Salazar E, Bertholf RL. Rational use and interpretation of urine drug testing in chronic opioid therapy. Ann Clin Lab Sci. 2007;37:301-314.
  8. 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. 

© American Society of Pain Educators


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