An opinion paper published online in JAMA Psychiatry casts doubt on the usefulness of pharmacogenetic (Pgen) tests in guiding choices and doses of psychiatric medications for patients with major depressive disorder and other mental health conditions.
“While the promise of Pgen-guided medication treatment of psychiatric disorders is appealing and supports the popular narrative of personalized/precision medicine, available evidence suggests that Pgen testing will not contribute much to improving care, if at all,” said first author George S. Zubenko, MD, PhD, University of Pittsburgh School of Medicine (retired). “And, in some cases, it could provide misleading information.”
Dr. Zubenko and coauthors write that in most cases major depressive disorder is determined by numerous genes, and no single gene or limited set of genes—including those affecting drug metabolism and drug targets—determine more than a few percent of illness risk or treatment course. Much more important than inherited determinants of drug metabolism and response, the writers contend, are demographic and environmental factors, a patient’s general health, clinical characteristics involving psychiatric symptoms, severity, and comorbidity, and comedication.
Furthermore, while the activity of metabolic enzymes is heritable, extremely fast or slow metabolism is actually rare, and dosing should be guided by careful choice and monitoring of therapeutic and side effects, the authors write. Standard evidence-based protocols are already available to assist in choosing medication.
"Doctors, patients, and family members should understand that the jury is out on whether Pgen testing improves good psychiatric care performed by board-certified psychiatrists,” said Dr. Zubenko.
According to the Viewpoint column, 10 published effectiveness studies on Pgen contained significant flaws in design, implementation, and analysis. None were adequately blinded and properly controlled, and studies cited in promotional materials included researchers from companies that offer Pgen services.
"New technologies, when properly tested, should become part of clinical assessment, but Pgen has not passed such tests," said author Bruce M. Cohen, MD, PhD, neuropsychiatric research director at McLean Hospital, Belmont, Massachusetts.