Patients in medical treatment for attention deficit/hyperactivity disorder (ADHD): Are they at risk in drug screening?

The use of medicines to treat attention deficit/hyperactivity disorder (ADHD) has increased worldwide, including the use of amphetamine-based medicines or prodrugs that metabolise to amphetamine in vivo. At the same time, drugs-of-abuse testing by non-specific, point-of-care immunoassay methods ('quick tests') has increased. This article discusses the risk of 'false positive' results or post-analytical misinterpretations of results when immunoassays are used to analyse biological samples from ADHD patients. A rapid evidence review was conducted to identify studies that have focused on the risk of 'false positive' test results in immunoassay testing of patients treated with atomoxetine, bupropion, clonidine, guanfacine, methylphenidate, and modafinil. There is only evidence to suggest that bupropion should cause 'false positive' immunoassay results. However, there is a lack of systematic, updated evaluations and validations of cross-reactivity patterns for immunoassays in the literature. Advanced laboratory methods can distinguish the use of medicines from illicit amphetamine by stereospecific analysis of dextro- and levoamphetamine; however, these analytical services are not commonly available for routine drug testing. The present situation calls for more awareness, proper education and information on these critical ethical issues in drug testing, both for clinicians, other healthcare professionals involved in drug testing and for patients in medical treatment for ADHD. The pitfalls of immunoassays due to cross-reactivity and insufficient specificity/sensitivity can have serious negative consequences for patients safety with regard to incorrect laboratory drug-testing results. Consequently, confirmatory laboratory analysis should always be performed for 'presumptive' positive immunoassay screening results.