Use of PHQ-9 and pharmacogenetic testing in clinical practice.

Background: This project evaluated the clinical use of pharmacogenetic testing in an outpatient psychiatric practice, integrated a standardized measure for assessing depressive symptoms, and captured data regarding treatment efficacy.

Local Problem: According to the Centers for Disease Control and Prevention (2016), more than 10% of all outpatient office visits include a depression-related diagnosis. Patients who require more medication trials to experience remission of depressive symptoms are more likely to relapse in the follow-up period than those who do not (National Institute of Mental Health, 2001).

Methods And Interventions: Baseline Patient Health Questionnaire-9 (PHQ-9) scores and medication regimens were recorded for 15 adults with major depressive disorder who completed pharmacogenetic testing. Repeat PHQ-9 scores and medication regimens were recorded at follow-up appointments within 6 weeks post-pharmacogenetic testing and compared with baseline data.

Results: The PHQ-9 scores ranged from a 5-point reduction to a 2-point increase in depressive symptoms at follow-up appointment. The PHQ-9 scores were lower at follow-up screening for 14 participants. Six of the 15 participants were on a single medication, with significant drug-gene interactions. Medications with significant drug-gene interactions were eliminated from the regimen for three of the six patients. For the remaining three patients, providers deemed it to be reasonable to continue the medications with significant drug-gene interactions.

Conclusions: Pharmacogenetic testing is a useful clinical tool for guiding medication selection but does not replace provider judgment. Drug-gene interaction testing results should be considered in addition to patient preference, medication cost, possible side effects, and immediate clinical needs.