![]() However, because the assays do not measure the drugs of abuse or their metabolites directly, immunoassays are vulnerable to interferences. Urine immunoassays are widely used to monitor drug use. ![]() Table 1 shows the results of 7 patient urine samples that gave positive methadone immunoassay results and whose medical records Discussion It takes approximately 7500 ng/ml of vortioxetine in the immunoassay to generate a positive result, thus demonstrating cross-reactivity of 4% for vortioxetine in the MDN2 assay. Any signal above zero is reported as positive. 1 shows a graph of a spiking experiment, in which vortioxetine was added to deionized water to test for immunoreactivity in the MDN2 assay. This work was performed as part of a clinical quality assurance Resultsįig. The Core Laboratory processes samples from inpatients and outpatients at MGH. Setting and patientsĪll patient samples were submitted to the Massachusetts General Hospital (MGH) Core Laboratory for drug of abuse testing as ordered by the patient's treating clinician. A working methanolic stock (1 mg/ml) was prepared gravimetrically and used to make diluted standard solutions via dilution with deionized water. Vortioxetine: HBr was from Astatech, Inc. In our institutional experience, few of the positive screens are sent for confirmatory testing, suggesting that clinicians are relying on the MDN2 result as the primary laboratory evidence for methadone use. At the request of the ordering provider, the sample can be sent to a reference lab for confirmation by GC/MS. However, routine use of confirmatory MS methods is currently limited by cost and availability.Īt our institution, we use the Roche Kinetic Interaction of Microparticles in Solution (KIMS) Methadone II Urine immunoassay (hereafter MDN2) to screen for the presence of methadone in urine. Confirmatory testing by mass spectrometry after chromatography (LC/MS or GC/MS) for a specific drug or its metabolites is the most specific and sensitive test for the presence of that substance. Clinicians are increasingly aware of these imperfections, as reviewed elsewhere. ![]() Īs indirect methods, immunoassays are prone to false positives by design. Between 20, the College of American Pathologists (CAP) saw a 55% increase in the volume of proficiency testing for methadone immunoassays and a 588% increase for fentanyl immunoassays. The CDC recommends urine testing before prescribing opiates and at least annually to “assess for prescribed medications as well as other controlled prescription drugs and illicit drugs”. UDT is used to verify that a patient is adherent with prescribed medications and abstaining from illicit drug use. The last decade has seen a sustained epidemic of opioid use and abuse and a concomitant increase in the demand for urine drug testing (UDT).
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