I'm currently conducting a meta-analysis of pharmacist-led health interventions and their effect on levels of medication adherence. One of my studies has a phased intervention design. This means that Group A of participants received the intervention first, and three months later Group B of participants received the same intervention. Both groups were measured using the same tool for medication adherence. The study presents medication adherence means for both groups, at baseline, 3 months and 6 months post-intervention.
If I want to include this study in my meta-analysis, can I just take the overall mean level of medication adherence of the two groups (A & B) for each time point?