Utility and adoption of CYP2D6 and CYP2C19 genotyping and its translation into psychiatric clinical practice

Objective: To describe clinical utility and adoption of routinely offered CYP2D6 and CYP2C19 genotyping (CYP test) in daily clinical practice of a psychiatric centre. Method: We described psychiatrists translations of CYP test results in patients with genotypes indicating poor or ultrarapid metabolizer status and treated with at least one CYP-dependent drug based on a retrospective review of medical records. Complementary, we used ethnographic participant observation and qualitative interviews to identify the barriers and incentives for the use of CYP test results. Results: The cohort study included 101 of 1932 cases genotyped between 2003 and 2009. In 53 of 101 cases, test results were addressed in medical records. The most frequent response was to monitor drug concentrations (23 cases), observe for adverse events (18 cases) and adjust dosage (13 cases). In 33 of 101 cases, results were mentioned in the discharge letter. The ethnographic study indicated a poor adoption of the CYP test in clinical praxis. Test results were lost in workflows and knowledge transfer between laboratory and clinician and were absent from clinical routines, treatment conferences and educational fora. Conclusion: The CYP test has not gained foothold in clinical practice, and its potential clinical benefits are not utilized.