Langman, Loralie J.

Abstract: Urine drug testing (UDT) is an important laboratory tool utilized in various healthcare settings to identify drug or toxic exposures. It has wide clinical applications, including but not limited to detecting substance misuse, monitoring treatment effectiveness and compliance, and identifying substances in affected patients. Depending on the clinical care setting and patient population, the UDT service model and practice are important decisions by the clinical laboratory to meet the needs of the healthcare providers. In addition, clinical laboratories must appreciate the testing process and unique aspects of this toxicology test, from specimen collection and integrity, testing methods, to the result reporting and interpretation. Each phase has specific quality requirements to ensure the accuracy and appropriate interpretation of results. This review aims to summarize the preanalytical, analytical, and postanalytical considerations of clinical laboratories when implementing the test or providing support to clinicians in point-of-care settings. To bring awareness of the limitations inherent to different analytical methodologies, this review discusses important considerations and presents the current gaps, opportunities, and recommendations for quality improvement and standardization. This article may serve as a framework for clinical laboratory directors and other laboratory professionals to review their current provision of UDT and provide recommendations on various important aspects when considering changes to the test service models to meet their local clinical needs, including when introducing new test methods. It may also help physicians and healthcare providers appreciate the complexities of UDT and recognize the challenges in clinical interpretation.

Abstract Background DPYD testing can identify patients at risk for severe toxicity when a standard fluoropyrimidine antineoplastic dose is prescribed. Sequencing-based methods detect rare variants, which require classification. Methods DPYD sequencing results over a 9-year period through to 2024 were analyzed. The dataset was filtered to calculate the positive test rate for different genotyping strategies, including targeted analysis of the Association for Molecular Pathology (AMP) Tier 1 and 2 recommended alleles, and as compared to sequencing. Variant classifications based on the laboratory’s clinical protocol were compared to ClinVar classifications and designations by the Clinical Pharmacogenetics Implementation Consortium (CPIC) expert panel. Results A DPYD variant was reported in 12.79% (896/7003) of those tested, with 2.53% (170/7003) of all reports including a variant of uncertain significance. Had only AMP Tier 1 or both Tier 1 and 2 been tested, 9.30% and 9.44% of patients would have received a positive report, respectively. Among the 281 unique, non-Tier 1/Tier 2 variants encountered during sequencing, >80% were not classified by the CPIC expert panel, while >48% were not reported in ClinVar. Variant classifications by our laboratory and those in ClinVar were generally concordant with the CPIC expert panel, despite the lack of a standardized classification system. Conclusions While AMP Tier 1 genotyping would have identified most patients at risk for fluoropyrimidine toxicity, sequencing is more comprehensive, identifying 26% more reportable variants compared to targeted genotyping. A standard framework for pharmacogenomic variant classification could facilitate consistent variant classification and a transition from targeted genotyping to sequencing.

Context.— Clinical laboratories are increasingly implementing pharmacogenomic (PGx) testing. Although PGx is similar to genetic testing for other indications, there are unique aspects that laboratories should consider. Objective.— To aid clinical laboratories that are implementing clinical PGx testing by describing characteristics of PGx test design and validation, as well as approaches to reporting. Resources that are useful for clinical laboratories performing PGx testing will be highlighted. Design.— The College of American Pathologists formed a workgroup composed of laboratorians with expertise in clinical PGx testing. The workgroup included representatives from the Association for Molecular Pathology and the American College of Medical Genetics and Genomics. The workgroup reviewed pertinent literature, as well as experience from proficiency testing and from members’ laboratories. Results.— The workgroup recommends that laboratories implementing PGx consider the following concepts: testing platform, test design (ie, selection of pharmacogenes and variants/alleles), use of reference materials during test development and as controls during clinical runs, star allele and standard nomenclature systems, translations from genotype to predicted phenotype, and considerations for result reporting including making medication recommendations. The workgroup provides considerations when using report vendors, emphasizing the clinical laboratory’s role and responsibility when implementing such reporting tools from vendors. Conclusions.— Clinical laboratories should be familiar with the fundamentals of PGx, ensure that PGx testing meets the applicable regulatory requirements for all aspects of the clinical laboratory testing process, and follow recommendations for standardization of nomenclature and reporting.

Abstract Background Alcohol biomarkers including ethyl glucuronide (EtG) and phosphatidylethanol (PEth) are ordered frequently in clinical and forensic settings including solid organ transplantation. PEth provides a long detection window but can be insensitive to light drinking. In contrast, EtG and ethyl sulfate (EtS) can be elevated after light alcohol consumption and might complement PEth testing. Methods Urine EtG/EtS and whole blood PEth results were evaluated from all clinically-ordered testing between 2014 and 2024. PEth and EtG/EtS confirmation were performed by liquid chromatography tandem mass spectrometry at two reference laboratories, using cutoffs: Lab A, PEth 20 ng/ml, EtG and EtS 500 and 250 ng/ml; Lab B, PEth 10 ng/ml, EtG and EtS 250 and 100 ng/ml. Only Lab B performed EtG screening by immunoassay, using a 500 ng/ml cutoff. Results Phosphatidylethanol was positive in 1269 (15.6%) of 8131 samples, compared to 769 (6.7%) confirmed EtG/EtS positives from 11 555 samples. EtG screening (n = 9668) was positive in 743 (7.7%) samples, of which 30 (4.0%) confirmed negative (false positives); the screen was indeterminate in 267 (2.8%) samples, 66 of which confirmed positive and 172 negative. Of 3132 paired PEth and EtG samples, 2887 (92.2%) were concordant, 224 (7.2%) were PEth-positive, and 21 (0.7%) were EtG-positive. PEth was significantly more sensitive in paired samples (P < .001), even after accounting for potential confounders such as transfusion. Limiting testing to PEth would have correctly identified alcohol consumption in 331 of 373 (88.7%) instances versus EtG/EtS in 149 (39.9%), and reduced charges by >$720 000 USD. Discussion Phosphatidylethanol outperformed EtG/EtS in detecting alcohol consumption in a predominantly abstinent transplant population. Compared to PEth, EtG/EtS had lower overall positivity and poorer sensitivity in paired samples; additionally, EtG screening demonstrated false positives and indeterminate results. EtG testing provided little added value beyond PEth in this population, and did not warrant the increased cost of performing both tests.

Abstract: The Immunosuppressive Drugs Scientific Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology established the second consensus report to guide therapeutic drug monitoring (TDM) of everolimus (EVR) and its optimal use in clinical practice 7 years after the first version was published in 2016. This version provides information focused on new developments that have arisen in the last 7 years. For the general aspects of the pharmacology and TDM of EVR that have retained their relevance, readers can refer to the 2016 document. This edition includes new evidence from the literature, focusing on the topics updated during the last 7 years, including indirect pharmacological effects of EVR on the mammalian target of rapamycin complex 2 with the major mechanism of direct inhibition of the mammalian target of rapamycin complex 1. In addition, various concepts and technical options to monitor EVR concentrations, improve analytical performance, and increase the number of options available for immunochemical analytical methods have been included. Only limited new pharmacogenetic information regarding EVR has emerged; however, pharmacometrics and model-informed precision dosing have been constructed using physiological parameters as covariates, including pharmacogenetic information. In clinical settings, EVR is combined with a decreased dose of calcineurin inhibitors, such as tacrolimus and cyclosporine, instead of mycophenolic acid. The literature and recommendations for specific organ transplantations, such as that of the kidneys, liver, heart, and lungs, as well as for oncology and pediatrics have been updated. EVR TDM for pancreatic and islet transplantation has been added to this edition. The pharmacodynamic monitoring of EVR in organ transplantation has also been updated. These updates and additions, along with the previous version of this consensus document, will be helpful to clinicians and researchers treating patients receiving EVR.

AbstractIntroductionPhosphatidylethanol (PEth) is a long‐term marker of alcohol consumption used frequently in clinical scenarios such as liver transplant evaluation. Recent cases have demonstrated that packed red blood cell (pRBC) transfusion creates the potential for artificial elevation or decrease of observed PEth concentrations in recipients. Very little is known about the prevalence or stability of PEth in pRBCs.MethodsApheresis and whole‐blood (WB) donations were tested for PEth using liquid chromatography – tandem mass spectrometry with limit of quantitation 10 ng/mL. Units were stored under routine blood bank conditions to evaluate the stability of PEth and the impact of irradiation.ResultsOver 40% of apheresis and WB donors had PEth ≥10 ng/mL (maximum observed 587 ng/mL). As WB units were processed into component pRBCs, PEth concentrations increased and were higher than donor WB levels (EDTA sample) prior to collection (maximum observed 711 ng/mL). Storage for up to 5 weeks post donation resulted in mean 17.3% decrease in PEth‐positive units; in contrast to a prior report, we observed no PEth formation in units with negative (<10 ng/mL) baseline concentrations. Irradiation of pRBCs did not substantially affect PEth concentrations in either PEth‐positive or PEth‐negative units.DiscussionPEth concentrations in healthy blood donors may potentially confound alcohol use or abstinence assessment in pRBC recipients. Transfusion medicine services and clinical practices such as transplantation and behavioral medicine should recognize this phenomenon and collaborate on testing protocols to appropriately interpret PEth in pRBC recipients.

Context.— Accurate interpretation of drug test results is key to appropriate patient care in numerous settings, including pain management. Despite recommendations that providers should consult laboratory professionals for guidance when necessary, literature demonstrating laboratorian expertise in drug test interpretation is lacking. Objective.— To evaluate participating laboratories’ performance on the case-based, interpretive (“dry”) challenge included with each Drug Monitoring for Pain Management proficiency testing program from 2012–2023. Design.— All challenges (n = 23) required participants to identify if drug test results were consistent or inconsistent with prescribed medications in the case history. Relevant medications, presumptive and confirmatory drug test results, and participant responses were extracted from program summary reports and examined for performance and common themes. Results.— Overall, 91.8% (6821 of 7431) of participant responses correctly identified whether drug testing was consistent with medications. There were 8 challenges with participant scores less than 91.8% (range, 59.8% [49 of 82 responses] to 88.9% [193 of 217 responses]). Common knowledge gaps identified in these challenges included false-positive presumptive (screening) results, minor metabolism of opiates, and recognizing that presence of a nonprescribed drug is inconsistent with prescribed medications. Although some participants repeatedly responded incorrectly, there were no associations between laboratory type, personnel responding, or analytical performance and incorrect responses to interpretative challenges. Conclusions.— Program participants performed well overall, but several concerning educational gaps were identified. Laboratorians have a role in providing interpretative guidance for drug testing and should emphasize ongoing education to ensure competence in the setting of constantly changing prescribed and nonprescribed drug use.

CYP2D6 duplication has important pharmacogenomic implications. Reflex testing with long-range PCR (LR-PCR) can resolve the genotype when a duplication and alleles with differing activity scores are detected. We evaluated whether visual inspection of plots from real-time-PCR-based targeted genotyping with copy number variation (CNV) detection could reliably determine the duplicated CYP2D6 allele. Six reviewers evaluated QuantStudio OpenArray CYP2D6 genotyping results and the TaqMan Genotyper plots for seventy-three well-characterized cases with three copies of CYP2D6 and two different alleles. Reviewers blinded to the final genotype visually assessed the plots to determine the duplicated allele or opt for reflex sequencing. Reviewers achieved 100% accuracy for cases with three CYP2D6 copies that they opted to report. Reviewers did not request reflex sequencing in 49–67 (67–92%) cases (and correctly identified the duplicated allele in each case); all remaining cases (6–24) were marked by at least one reviewer for reflex sequencing. In most cases with three copies of CYP2D6, the duplicated allele can be determined using a combination of targeted genotyping using real-time PCR with CNV detection without need for reflex sequencing. In ambiguous cases and those with >3 copies, LR-PCR and Sanger sequencing may still be necessary for determination of the duplicated allele.

The COVID-19 pandemic has significantly impacted the production, distribution, and demand of essential laboratory supplies worldwide. In 2021, severe shortages in required laboratory supplies such as blood collection tubes, butterfly needles, and blood gas syringes became a critical issue across Canada. Many hospitals or institutions had to instruct physicians and patients to limit laboratory testing where possible and, in some cases, required emergency shipments of tubes from alternative vendors or nearby hospitals. Laboratory testing is ubiquitous in managing patients. It is used for screening, diagnosis, and monitoring purposes. With limited blood collection tubes, consideration for restricting non-urgent testing is needed to conserve supply and protect acute care departments that manage critically ill patients. In addition, laboratories across Canada have experienced significant staffing shortages, resulting in an even greater need for appropriate laboratory utilization. Consequently, the Canadian Society of Clinical Chemists (CSCC) and the Canadian Association of Medical Biochemists (CAMB) curated utilization recommendations for both hospital and primary care settings in collaboration with Choosing Wisely Canada (CWC). These recommendations were specifically selected from those previously published by Choosing Wisely Canada (CWC), with impact statements and rationales added to conserve at-risk laboratory resources. Supply chain disruptions of clinical laboratory resources are expected to continue throughout 2022, indicating that now, more than ever, a focus on appropriate laboratory utilization is essential.

Abstract: Nirmatrelvir/ritonavir (Paxlovid) consists of a peptidomimetic inhibitor (nirmatrelvir) of the SARS-CoV-2 main protease and a pharmacokinetic enhancer (ritonavir). It is approved for the treatment of mild-to-moderate COVID-19. This combination of nirmatrelvir and ritonavir can mediate significant and complex drug–drug interactions (DDIs), primarily due to the ritonavir component. Indeed, ritonavir inhibits the metabolism of nirmatrelvir through cytochrome P450 3A (CYP3A) leading to higher plasma concentrations and a longer half-life of nirmatrelvir. Coadministration of nirmatrelvir/ritonavir with immunosuppressive drugs (ISDs) is particularly challenging given the major involvement of CYP3A in the metabolism of most of these drugs and their narrow therapeutic ranges. Exposure of ISDs will be drastically increased through the potent ritonavir-mediated inhibition of CYP3A, resulting in an increased risk of adverse drug reactions. Although a decrease in the dosage of ISDs can prevent toxicity, an inappropriate dosage regimen may also result in insufficient exposure and a risk of rejection. Here, we provide some general recommendations for therapeutic drug monitoring of ISDs and dosing recommendations when coadministered with nirmatrelvir/ritonavir. Particularly, tacrolimus should be discontinued, or patients should be given a microdose on day 1, whereas cyclosporine dosage should be reduced to 20% of the initial dosage during the antiviral treatment. Dosages of mammalian target of rapamycin inhibitors (m-TORis) should also be adjusted while dosages of mycophenolic acid and corticosteroids are expected to be less impacted.