Objectives Our previous retrospecive study evaluating the appropriateness of serum digoxin concentration (SDC) measurements revealed errors in the timing of blood specimen collection in 98% of the tests. The aim of this study is to evaluate the appropriateness of the SDC measurements and the factors involved in inappropriate test-ordering, after training health personnel in digoxin therapeutic drug monitoring.

Methods This is a training-based quasi-experimental study. The residents and nurses of the Cardiology Clinic were trained first in December 2017, and refresher training courses were carried out every month throughout the study. The medical data of the inpatients receiving digoxin therapy were recorded prospectively, between January and December 2018. The appropriateness of the physicians’ orders for SDC measurement was evaluated according to the criteria of the right indication and right timing of blood collection. The results are presented by descriptive statistics, Student’s t-test and χ² analysis.

Results A total of 232 SDC tests were ordered for 121 patients (age: 71.0±12.6 years, 56.2% women). Of these orders,129 (55.6%) were considered appropriate: 205 (88.4%) for indication and 129 (62.9%) for blood collection timing. There was a significant correlation between inappropriate order for SDC test and the age of the patient, female gender, impairment of renal function tests, high levels of serum BNP and the number of medications used (P<0.005).

Conclusions Approximately a one-half decrease in inappropriate tests compared with our previous study results imply that education has a positive effect on physician behaviour. However, physicians’ concerns due to increased risk factors for the patient still play a role in inappropriate test-ordering.