The overall study design was a repeated measures assessment of DDI knowledge among advanced pharmacy students. Third-year students were invited to participate in an evaluation of their DDI knowledge immediately before and after a DDI educational session during their final classroom lecture-based year of study in the University of Arizona PharmD program. The learning objectives for the educational session included: (1) defining DDIs; (2) listing and identifying 11 clinically important DDIs from case scenarios; (3) explaining the difference between pharmacodynamic and pharmacokinetic mechanisms of DDIs; (4) describing management strategies for 11 clinically important DDIs; and (5) listing DDI information resources. At the time of the session, assessment of knowledge was conducted immediately prior to and after a 1½-hour lecture with case discussions. The purpose of the educational session was not only to train students in these 11 clinically significant DDIs, but also to teach general mechanisms and management of interactions so that students could apply this knowledge to all DDIs. Results from the pre- and post-intervention assessment are reported in detail in a separate publication.25
All students were given the option to present short DDI vignettes to health care professionals anytime during their fourth-year advanced pharmacy practice experiences (APPEs) as a means to reinforce DDI knowledge. If they chose to do so, they could create and present 3 DDI vignettes in place of 1 of their required drug information assignments during any APPE. Because the materials necessary to create the vignettes were provided to the students, making them easier to complete than the drug information assignments, the instructors expected several students to choose this option and present DDI vignettes during their fourth year. The clinical content of the vignette presentations included methods to identify DDIs, mechanisms that cause the interaction, the resulting consequences, potential therapeutic alternatives that could be used to avoid the DDI, or monitoring parameters for when concurrent use of interacting drugs is deemed appropriate. Each case vignette lasted approximately 5 minutes. After each presentation, students reported the following information to the researchers via a post card: (1) date of the presentation; (2) number and type of health care providers who attended the vignette (ie, nurse practitioners, pharmacists, physicians, and other healthcare professionals); (3) practice setting in which the case was presented (eg, managed care, hospital pharmacy, community pharmacy); (4) city in which the clerkship site was located; (5) DDI case that was presented and why it was selected; and (6) whether they would present the case again and why.
After completing all of their APPEs, fourth-year students completed the same DDI knowledge assessment tool administered 1 year earlier, after completion of the DDI education session. For all 3 administrations of the DDI knowledge assessment, students completed the questionnaire without using reference materials.
The DDI management strategy response categories that the students chose from included: (1) avoid combination; (2) usually avoid combination; (3) take precautions; (4) no special precautions; and (5) not sure. The “not sure” option was included to prevent guessing. Warholak and colleagues conducted a study that assessed the use of this instrument using Rasch analysis and found that it demonstrated validity and reliability in this population.26
The DDI questionnaire consisted of 15 drug pairs. Among the 15, one “avoid combination” pair of drugs was included for which concurrent use was contraindicated (ie, risk of the combination outweighs the benefits of treatment); 5 “usually avoid combination” pairs were included for which the drugs should usually not be used together except in special circumstances; 5 “take precautions” pairs of drugs for which concurrent use could be managed by increased monitoring or dose adjustment were provided; and 4 “no special precautions” pairs were included for which the drugs most likely did not interact and therefore the risk of having an adverse event was small.
Two different outcome variables were used to evaluate the main study outcomes. The first outcome was change in DDI recognition knowledge, where students were awarded credit if they correctly identified a potential DDI regardless of the level of precaution that is required. The second outcome was change in DDI management strategy knowledge, where students had to select the correct management strategy (ie, avoid, usually avoid, take precautions, or no precautions necessary) to be awarded credit. The same DDI pairs that were discussed in the educational session were included in the pre-intervention, post-intervention, and 1-year follow-up assessments. Demographic information on age, gender, and percentage of students with previous health-related degrees also were collected.
An analysis was conducted to compare those students who completed both the post-intervention and one-year follow-up assessment to those who only completed the post-intervention assessment. The investigators hypothesized that students who completed the entire process of the study would have higher overall 1-year follow-up assessment scores. Wilcoxon rank-sum test was used to determine whether significant differences existed among the sum of the students’ post-intervention test scores along with whether the age of the student impacted their post-intervention test scores. Chi-square analyses were used to determine whether gender and having a previous health-related degree impacted post-intervention test results.
Multiple-linear regression models27
were used to assess whether vignette presentations given over the course of the APPEs affected DDI recognition or DDI management strategy knowledge. The presentation of any case vignettes (ie, at least 1 case vignette) and the quantity (ie, amount of case vignettes presented varied) of case vignettes presented were both assessed for knowledge retention.
A secondary investigation was undertaken to determine whether students who provided any DDI vignette presentations were better at correctly recognizing interactions (the DDI recognition scoring strategy) or indicating the proper management of DDIs (the DDI management scoring strategy) on the 1-year post-intervention test compared to students who did not complete any case presentations. Chi-square analysis was conducted to determine whether significant differences existed between those who presented any cases versus those who presented no cases.
The investigators hypothesized that students who presented any DDI cases would be better able to recognize clinically significant DDIs and identify the appropriate management strategy and that students who presented a specific DDI would be better able to recognize and identify the appropriate management strategy for that DDI when taking the final follow-up assessment 1 year after the DDI training session.
An alpha (α) level of 0.05 was used for significance with 95% confidence intervals reported for all point estimates. Bonferroni corrections were used where appropriate. All statistics were conducted in Intercooled STATA, version 11.0 (StataCorp, College Station, TX). Absolute differences were measured among baseline test/post-intervention test; post-intervention test/1-year follow-up test; and baseline test/1-year follow-up test. Frequencies and percentages were calculated for the case presentation attendees, setting, and specific DDI selected for the vignette.