Drug testing is increasingly becoming an important part of responsible prescribing practices. Drug testing can alert medical providers to indications of drug abuse or misuse, as well as allow them to monitor for patient compliance with prescription regimens. However, while the medical utility of routine drug testing is becoming apparent, it is important to understand that many of its methodologies were initially developed for forensic and employment-testing applications. Accordingly, traditional approaches to drug testing do not always meet the demands of the clinical context.
The traditional approach to drug testing begins with a drug screen. Drug screens are typically “quick and dirty” immunoassay tests. They are cost effective and have short turnaround times, but they are not particularly sensitive, selective, or accurate, being prone to both false positives and false negatives. Therefore, positive drug screen results are considered to be “presumptive” and must be confirmed by a definitive method (gas or liquid chromatography-mass spectrometry).
The approach of drug screening followed by confirmation testing of positive results is understandable in forensic or employment-testing applications, in which only positive results are potentially troubling. However, in the clinical setting, unexpected negative results can often be concerning as well, as they can indicate prescription noncompliance. In such cases, there can be ample indication for confirmatory testing of both negative and positive drug screen results. Therefore, it may make more sense to skip the drug screen altogether and proceed directly to confirmation testing in order to avoid the risk of false negatives and prevent unnecessary tests. (After all, what is the point of a screen if both positive and negative results require confirmation?) This is made quite feasible considering that confirmation testing panels are often wide-ranging and can be made to encompass nearly every drug class contained in a conventional drug screen panel and more.
At Southeast Clinical Laboratories, we appreciate the need for conventional drug screens in the clinical setting, but we also offer a range of direct-to-confirmation panels to appropriately meet the more demanding needs of prescription monitoring. It is important to understand that clinical drug testing is not “one size fits all”—the testing approach should be sensitive to individual circumstances and needs.
Steven Sartor, PhD serves as the Director of Toxicology for Southeastern Labs.
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