Oxaprozin cross-reactivity in three commercial immunoassays for benzodiazepines in urine

What Can a Urine Drug Screening Immunoassay Really Tell Us?

Urine drug screening has become standard of care in many medical practice settings to assess compliance, detect misuse, and/or to provide basis for medical or legal action. The antibody-based enzymatic immunoassays used for qualitative analysis of urine have significant drawbacks that clinicians are often not aware of. Recent literature suggests that there is a lack of understanding of the shortcomings of these assays by clinicians who are ordering and/or interpreting them. This article addresses the state of each of the individual immunoassays that are most commonly used today in order to help the reader become proficient in the interpretation and application of the results. Some literature already exists regarding sources of "false positives" and "false negatives," but none seem to present the material with the practicing clinician in mind. This review aims to avoid overwhelming the reader with structures and analytical chemistry. The reader will be presented relevant clinical knowledge that will facilitate appropriate interpretation of immunoassays regardless of practice settings. Using this review as a learning tool and a reference, clinicians will be able to interpret the results of commonly used immunoassays in an evidence-based, informed manner and minimize the negative impact that misinterpretation has on patient care.

‘False-positive’ and ‘false-negative’ test results in clinical urine drug testing

The terms ‘false-positive’ and ‘false-negative’ are widely used in discussions of urine drug test (UDT) results. These terms are inadequate because they are used in different ways by physicians and laboratory professionals and they are too narrow to encompass the larger universe of potentially misleading, inappropriate and unexpected drug test results. This larger universe, while not solely comprised of technically ‘true’ or ‘false’ positive or negative test results, presents comparable interpretive challenges with corresponding clinical implications. In this review, we propose the terms ‘potentially inappropriate’ positive or negative test results in reference to UDT results that are ambiguous or unexpected and subject to misinterpretation. Causes of potentially inappropriate positive UDT results include in vivo metabolic conversions of a drug, exposure to nonillicit sources of a drug and laboratory error. Causes of potentially inappropriate negative UDT results include limited assay specificity, absence of drug in the urine, presence of drug in the urine, but below established assay cutoff, specimen manipulation and laboratory error. Clinical UDT interpretation is a complicated task requiring knowledge of recent prescription, over-the-counter and herbal drug administration, drug metabolism and analytical sensitivities and specificities.

Random drug testing to reduce the incidence of addiction in anesthesia residents: preliminary results from one program

Substance abuse occurs in approximately 1%-2% of anesthesia residents and nearly 80% of programs have had one or more resident (s) with such a problem. Education and control efforts have failed to reduce the frequency of substance abuse. Anesthesia providers have a professional obligation to be drug-free for the well being of their patients. We have instituted a program of preplacement and random urine testing of residents in anesthesiology in an attempt to decrease the incidence of substance abuse. We demonstrate that such a program is feasible, despite logistic and cultural obstacles. Larger multi-institutional studies will be required to determine whether instituting a program of random urine testing decreases the incidence of substance abuse in anesthesiology residents.

Urine drug screening: practical guide for clinicians

Drug testing, commonly used in health care, workplace, and criminal settings, has become widespread during the past decade. Urine drug screens have been the most common method for analysis because of ease of sampling. The simplicity of use and access to rapid results have increased demand for and use of immunoassays; however, these assays are not perfect. False-positive results of immunoassays can lead to serious medical or social consequences if results are not confirmed by secondary analysis, such as gas chromatography-mass spectrometry. The Department of Health and Human Services' guidelines for the workplace require testing for the following 5 substances: amphetamines, cannabinoids, cocaine, opiates, and phencyclidine. This article discusses potential false-positive results and false-negative results that occur with immunoassays of these substances and with alcohol, benzodiazepines, and tricyclic antidepressants. Other pitfalls, such as adulteration, substitution, and dilution of urine samples, are discussed. Pragmatic concepts summarized in this article should minimize the potential risks of misinterpreting urine drug screens.

Hypothesis on interferences in kinetic interaction of microparticles in solution (KIMS) technology

The present paper describes an evaluation of the interferences found with an immunochemical drug test performed during a workplace control. During the period 1993–2003 more than 200,000 urine samples from workers were examined by the Italian Air Force. Samples were screened for drugs of abuse (opiates, cocaine, cannabinoids, amphetamines, methadone) using an immunochemical technique (Roche, kinetic interaction of microparticles in solution, KIMS). A total of 520 positive samples were sent to the Forensic Toxicology Laboratory for confirmation by gas chromatography/mass spectrometry (GC/MS). Approximately 39% of these were found to be true positives. For the remaining samples, pharmacological therapy in subjects was estimated to evaluate possible interferences due to medicine intake. Our study showed a high frequency of false-positive results with this immunochemical technique, mainly for the cannabinoid and amphetamine groups. Recurrent references to some medicines during subject anamnesis were noted.

Clin Chem Lab Med 2006;44;894–7.

The association of race and ethnicity with rates of drug and alcohol testing among US trauma patients

BACKGROUND

Racial and ethnic minority patients often receive differential medical care compared to Caucasians. The aim of this study was to evaluate the association of race and ethnicity with rates of alcohol and drug testing among adult US trauma patients.

METHODS

Data for 79,246 adults admitted to 58 institutions participating in the US National Trauma Data Bank were evaluated using multivariable, hierarchical, mixed-effects analyses to determine the odds of receiving alcohol and drug testing among different racial/ethnic groups. The primary outcome variable was whether an alcohol or drug test was performed. The secondary outcome variable was the results of those tests. Participants were stratified by injury severity using the Injury Severity Score. Additional case-mix variables included: gender, age, Glasgow Coma Scale, day and time of arrival, and payment source.

RESULTS

Black and Hispanic males in all injury severity groups were tested for alcohol more frequently than Caucasian males (odds ratio for Black men 1.31, 95% confidence interval 1.16-1.47; and for Hispanic men 1.45, 95% confidence interval 1.19-1.77, in the moderate injury group). Hispanic males in the moderate injury group were also tested for drugs more frequently then Caucasian males (odds ratio 1.33, 95% confidence interval 1.09-1.63).

CONCLUSION

Racial and ethnic minority trauma patients in the US are tested for alcohol and drugs at higher rates after adjusting for potential confounders. Because having a positive alcohol or drug test can adversely affect a patient's medical care, differential testing that is racially or ethnically biased may place minority patients at risk of receiving disparate care.