The Clinical Impact of a False-Positive Urine Cocaine Screening Result on a Patient's Pain Management

Abstract

Background: The urine of a patient admitted for chest and epigastric pain tested positive for cocaine using an immunoassay-based drug screening method (positive/negative cutoff concentration 150ng/mL). Despite the patient's denial of recent cocaine use, this positive cocaine screening result in conjunction with a remote history of drug misuse impacted the patient's recommended pain therapy. Specifically, these factors prompted the clinical team to question the appropriateness of opioids and other potentially addictive therapeutics during the treatment of cancer pain from previously undetected advanced pancreatic carcinoma. Objective: After pain management and clinical pathology consultation, it was decided that the positive cocaine screening result should be confirmed by gas chromatography-mass spectrometry (GC-MS) testing. Results: This more sensitive and specific analytical technique revealed that both cocaine and its primary metabolite benzoylecgonine were undetectable (i.e., less than the assay detection limit of 50ng/mL), thus indicating that the positive urine screening result was falsely positive. With this confirmation, the pain management service team was reassured in offering intrathecal pump (ITP) therapy for pain control. ITP implantation was well tolerated, and the patient eventually achieved excellent pain relief. However, ITP therapy most likely would not have been utilized without the GC-MS confirmation testing unless alternative options failed and extensive vigilant monitoring was initiated. Conclusion: As exemplified in this case, confirmatory drug testing should be performed on specimens with unexpected immunoassay-based drug screening results. To our knowledge, this is the first report of a false-positive urine cocaine screening result and its impact on patient management.