The use of pharmacogenetic (PGx) testing in patients with major depressive disorder (MDD) appears to limit the length of time spent in a psychiatric clinic if the testing is performed early in the stay. A retrospective analysis of a naturalistic pharmacist-led pilot implementation of PGx testing in a psychiatric hospital (Vitos Klinik Eichberg in Eltville, Germany) was conducted between November 2016 and July 2017. Results of the study were published in the journal Pharmacopsychiatry.

The investigators sought to evaluate the effect of a PGx-guided drug therapy on the length of hospitalization, rehospitalization rates, severity of depression, and number of antidepressant switches. Two groups of patients were assessed: (1) those who were offered PGx testing prior to beginning an antidepressant (intervention cohort; n=49) and (2) a control group of patients who were admitted to the hospital 1 year earlier (control cohort; n=94) — when PGx testing was not in use.

Those in the intervention cohort had significantly shorter lengths of hospital stay than those in the control cohort, after correcting for lengths of hospitalization and the time to results of genotyping (36.3 ± 19.3 days vs 46.6 ± 19.1 days; respectively; P =.003). Patients who were antidepressant naïve derived the greatest benefit from PGx testing (24.7 ± 13.5 days in the intervention arm vs 50.2 ± 22.5 days in the control arm; P <.001). The number of switches in antidepressant agents during the entire hospital stay did not differ significantly between the cohorts 0.41 ± 0.64 vs 0.21 ± 0.46, respectively; 95% CI, –0.015 to –0.472; P =.063).

Several drawbacks exist in the current study. Because of the limitations in the genotyping process (ie, only 4 patients received genotyping per week, time to genotyping results, taking a blood sample, and the time to initiating pharmacotherapy), no differences were found between the groups with respect to the length of hospital stay, if not corrected for the waiting time. It is possible that the effect might have been larger if all of the antidepressant therapies were initiated on the same day that genotyping results became available. In fact, beginning a new drug therapy was occasionally further delayed by a maximum of 6 days.


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The investigators concluded that although the findings from this retrospective analysis are promising, additional systematic prospective studies are warranted, in order to evaluate the impact of PGx testing on the treatment of patients with MDD. The presence of a pharmacist on the ward can facilitate the process of interpreting the genotyping results and assist in the development of a recommendation for a first-choice drug therapy.

Reference

Bättig VAD, Roll SC, Hahn M. Pharmacogenetic testing in depressed patients and interdisciplinary exchange between a pharmacist and psychiatrists results in reduced hospitalization times. Pharmacopsychiatry. 2020;53(4):185-192. doi: 10.1055/a-1096-1171