3.1 Characteristics of the study population
During the observation period from June 2018 to June 2020 135 patients underwent testing with the 16-gene PGx panel (Figure 1 ). Patient characteristics are presented in Table 1 , including a stratification over drug-specific indication vs. screening. Compared to 33 subjects with a screening indication, the 102 patients with a drug-specific indication for PGx testing were older (median 70 vs. 58 years) and took a higher number of drugs (median 6 vs. 3). The three most frequent drug-specific indications for PGx-testing were therapy with clopidogrel (n = 60), tamoxifen (n = 15) and polypsychopharmacotherapy (n = 9). Medications in the tested population were predominantly related to cardiovascular diseases, but we also observed frequent use of analgesics, antidepressants, antidiabetics and benzodiazepines.
Furthermore, drug-gene interactions may be particularly relevant in the presence of additional drug-drug interactions that affect the same metabolic pathway or in case of impaired renal function. It is therefore of interest that 19.3% of the study population took inhibitors of CYP2D6 and 8.2% of CYP2C19, and that 14.1% had an eGFR below 60 ml/min.