Although the past decade has seen a dramatic increase in prescribed analgesics for managing chronic pain, more than 40% of patients report that their pain is not treated adequately (1–3). At the same time, epidemiologic studies have shown a greater occurrence of opioid and drug misuse (4–8). As a consequence, clinicians face the challenge of providing their patients with necessary pain control while maintaining a low risk for substance abuse.
Urine drug testing (UDT) is an effective tool in pain management to monitor adherence to prescribed medications (9–11). In fact, national guidelines, such as those offered by the American Society of Interventional Pain Physicians, have recommended UDT not only to assess compliance but also to detect undisclosed substances and diversion (12–14). Therefore, the clinical laboratory must be equipped to offer an extensive test menu for UDT, including commonly prescribed medications and commonly abused drugs. The laboratory also must select a sensitive and specific method, as accurate and informative results are an important adjunct to clinical decision-making.
Most commonly, UDT is performed via a two-step process: an initial drug screen followed by confirmation or definitive testing for drugs/drug classes that screened positive. Immunoassay screens are typically the first line assays because they can be done at the point-of-care and are generally cost-effective. However, immunoassays have limitations. Most immunoassay screens detect the presence of a drug class (e.g. opioids) and not the individual drug (e.g. hydromorphone), so assessing compliance can be challenging. Moreover, because they are designed to cross-react with numerous drugs within a drug class, the antibodies also can cross-react with drugs outside that drug class—particularly if the drugs are present at high enough concentrations—thereby producing false positive results. Due to these limitations, all positive specimens should be reflexed to more specific, definitive testing such as liquid chromatography tandem mass spectrometry (LC-MS/MS) or gas chromatography mass spectrometry (GC-MS) (12–14).
The sensitivity of immunoassays is also problematic. Most were designed for the emergent setting or for workplace drug testing and have higher cutoffs than required to determine compliance. Additionally, specific drugs within each drug class will cross-react with the antibody at different concentrations, which could lead to false negative results (15–19). Several studies have suggested that negative screening results also should be confirmed by LC-MS/MS or GC-MS to achieve adequate sensitivity (15, 16, 19).
Due to mass spectrometry’s superior sensitivity and specificity, many laboratorians have advocated it as the first line testing methodology, particularly for frequently prescribed drugs such as opioids and benzodiazepines (15, 16, 19). Quantitative mass spectrometry also can provide information on the presence of particular metabolites, assisting in detecting urine adulteration or determining the parent compound(s) ingested. For example, patients who are prescribed buprenorphine can be monitored for compliance by the metabolite-parent (norbuprenorphine-buprenorphine) ratio. A ratio less than 0.02 is indicative of simulated compliance in which buprenorphine has been spiked directly into the urine sample (20). The relative concentrations of morphine, hydromorphone, and codeine by LC-MS/MS in patients prescribed morphine also help determine whether the prescribed medication and/or additional drugs were ingested. (21).
Most clinical laboratories are equipped to support UDT for evaluating acute intoxication or overdose. However, many laboratories do not offer an extensive test menu or the mass spectrometry testing necessary to support monitoring compliance in pain management. One of the major challenges of in-sourcing this testing is the high cost of instrumentation. Another is the need for highly trained personnel to interpret results and troubleshoot. Despite these challenges, laboratorians need to work with clinicians to offer the most sensitive and specific testing available. In this article, we describe our success with a phased approach to LC-MS/MS testing for pain management and its cost and technical benefits.
Implementation of LC-MS/MS Testing (Phase I)
From 2005 to 2008 in our laboratory, requests for UDT in pain management increased by an average of 33% per year. During this time, a reference laboratory performed our testing for pain management, and by 2008, send-out costs escalated to almost $1 million per year (22). To reduce costs, we proposed in-sourcing the majority of UDT for pain management over a 3-year period. Our proposal included an extensive test menu designed in collaboration with the Pain Management Center and contained both frequently prescribed drugs and pertinent drugs of abuse. In addition, we called for purchasing dedicated equipment (mass spectrometer and immunoanalyzer) and hiring a PhD scientist and medical technologist to develop and validate the testing.
Based on the high positivity rates of opioids and benzodiazepines and the limitations of existing immunoassays for these drug classes, we proposed LC-MS/MS as our first line test. We recommended for the remainder of drugs/drug classes a traditional immunoassay screen followed by mass spectrometry confirmation of positive screens performed by a reference laboratory.
Laboratory administration approved the proposal in 2009 based on projected cost savings and we implemented the plan in 2011 (22). After 3 years, our laboratory realized net savings of $978,690 (22). Clinicians appreciated the quality of testing and availability of on-site laboratory directors and residents to assist with test interpretation. In addition, by running tests 2 days per week, we were able to provide equivalent if not faster turnaround time for results. To ensure acceptable turnaround time, we trained three additional staff members in the toxicology area.
Implementation of LC-MS/MS Testing (Phase II)
In 2014 we performed another in-depth analysis of our testing algorithm for pain management to determine if we could expand our LC-MS/MS test menu. We considered the volume of testing, cost of remaining confirmatory send-outs and immunoassay screens, and accuracy of immunoassay screens, as well as our technical resources for test interpretation. Requests for UDT in pain management had increased significantly since 2008 and still included send-out costs for confirmation testing for the majority of drugs/drug classes. We also were using a dedicated analyzer to perform immunoassay screens, and paying for lease, service, and reagents for 10 drugs/drug classes.
It also concerned us that our false positive rates were as high as 12% (23). Importantly, in 2014 we had three technologists, a technical specialist, and a PhD scientist who were trained and competent in test interpretation, assay maintenance, and troubleshooting.
In order to further reduce costs and increase the sensitivity and specificity of our testing, we validated a new LC-MS/MS assay that simultaneously measures 36 drugs and metabolites. Our goal is to implement this new panel in early 2016. We expect that doing so will significantly reduce cost and eliminate all send-out and immunoassay testing. The only incremental increase in cost will be LC-MS/MS reagents, calibrators, and QC for the new analytes.
Challenges of Incorporating LC-MS/MS in the Laboratory
Despite the clinical and financial benefits of the new expanded panel, we anticipate some challenges. Our technical staff will be required to spend additional time interpreting test results and troubleshooting, but the phased approach should reduce any anxiety and shorten their learning curve. In addition, we will be able to automate and program the LC-MS/MS software to flag potential errors so that neither our technologist nor supervisor miss them. Our plan is to continue testing 2 days per week and shift the time previously spent on immunoassay screens to test interpretation.
In our current method we incubate samples with a beta-glucuronidase enzyme prior to testing and report total quantitative opioid and benzodiazepine levels (e.g. total morphine). The new sample preparation is dilute-and-shoot, without an enzyme incubation, which allows for decreased sample preparation time. These quantitative results will therefore differ from our current assay. In light of this, we have significantly lowered the lower limit of quantitation to accommodate for the lower concentrations of the free drug in urine. Furthermore, we will be reporting glucuronidated metabolites, such as morphine-6-glucuronide and morphine-3-glucuronide concentrations, in addition to free morphine concentrations. We will need to educate providers so they interpret their results correctly.
Finally, it is unclear what reimbursement our laboratory will receive for this new method. Despite the fact that definitive testing by LC-MS/MS is the preferred testing option for monitoring patients treated for chronic pain, many current payment models do not support LC-MS/MS for all patients. Laboratories and clinicians need to advocate for more reasonable reimbursement so that laboratories can be compensated for LC-MS/MS testing and are not forced to rely on inferior methods.
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Athena Petrides, PhD is instructor of pathology, Harvard Medical School, and assistant medical director, chemistry, and director, toxicology, Brigham and Women’s Hospital. Email: [email protected]
Stacy Melanson, MD, PhD is assistant professor of pathology, Harvard Medical School and associate medical director, clinical chemistry, Brigham and Women’s Hospital. Email: [email protected]
CLN's Focus on Mass Spectrometry is sponsored by Waters Corporation.