Person:

Krumme, Alexis

Objective: The use of retail purchasing data may improve adherence prediction over approaches using healthcare insurance claims alone. Design: Retrospective. Setting and participants A cohort of patients who received prescription medication benefits through CVS Caremark, used a CVS Pharmacy ExtraCare Health Care (ECHC) loyalty card, and initiated a statin medication in 2011. Outcome We evaluated associations between retail purchasing patterns and optimal adherence to statins in the 12 subsequent months. Results: Among 11 010 statin initiators, 43% were optimally adherent at 12 months of follow-up. Greater numbers of store visits per month and dollar amount per visit were positively associated with optimal adherence, as was making a purchase on the same day as filling a prescription (p<0.0001 for all). Models to predict adherence using retail purchase variables had low discriminative ability (C-statistic: 0.563), while models with both clinical and retail purchase variables achieved a C-statistic of 0.617. Conclusions: While the use of retail purchases may improve the discriminative ability of claims-based approaches, these data alone appear inadequate for adherence prediction, even with the addition of more complex analytical approaches. Nevertheless, associations between retail purchasing behaviours and adherence could inform the development of quality improvement interventions.

In the face of increasingly widespread availability and uptake of medications to treat and prevent cardiovascular disease, this dissertation is motivated by two broad research questions regarding the duration of cardiovascular therapy. First: how long should patients continue therapy when there are risks and benefits that may change over time? Second: how can continuation be encouraged when therapies are known to be safe and effective? In Aim 1, we compared exposure definitions of antiplatelet discontinuation versus continuation at 12 months after a drug-eluting coronary stent and associations with ischemic and bleeding events. We found that increasing restrictions on the definition of therapy continuation yielded results consistent with those from the Dual Antiplatelet Therapy trial, in particular through greater compliance with assigned exposure status during follow-up. Our results also suggest the potential for residual confounding by unmeasured characteristics, which for ischemic events may exaggerate effects of continuation, while for bleeding events may attenuate such effects, particularly if providers are monitoring and appropriately discontinuing therapy among patients at higher risk of bleeding. In Aim 2, we compared the long-term effectiveness and safety of prasugrel and clopidogrel. Among patients with acute coronary syndrome at the time of the coronary stent procedure, prasugrel use suggested ischemic benefit without increased risk of bleeding. In contrast, in patients with stable ischemic heart disease only, prasugrel use was not associated with ischemic benefit but was associated with increased risk of bleeding. For both groups, ischemic endpoint results are consistent with trial findings; for the bleeding endpoint, results may reflect differences in baseline bleeding risk. In Aim 3, we evaluated the impact of a pharmacy-based adherence improvement program on cardiovascular and healthcare outcomes. We found that adherence to cardiovascular medications improved by a small but significant amount among synchronized patients, with the largest improvements observed among patients with lowest baseline adherence level. Healthcare resource use decreased significantly, however cardiovascular clinical outcome rates did not differ between synchronized and control patients.

PURPOSE: Trajectory models have been shown to (1) identify groups of patients with similar patterns of medication filling behavior and (2) summarize the trajectory, the average adherence in each group over time. However, the association between adherence trajectories and clinical outcomes remains unclear. This study investigated the association between 12-month statin trajectories and subsequent cardiovascular events. METHODS: We identified patients with insurance coverage from a large national insurer who initiated a statin during January 1, 2007 to December 31, 2010. We assessed medication adherence during the 360 days following initiation and grouped patients based on the proportion of days covered (PDC) and trajectory models. We then measured cardiovascular events during the year after adherence assessment. Cox proportional hazards models were used to evaluate the association between adherence measures and cardiovascular outcomes; strength of association was quantified by the hazard ratio, the increase in model C-statistic, and the net reclassification index (NRI). RESULTS: Among 519 842 statin initiators, 8777 (1.7%) had a cardiovascular event during follow-up. More consistent medication use was associated with a lower likelihood of clinical events, whether adherence was measured through trajectory groups or PDC. When evaluating the prediction of future cardiovascular events by including a measure of adherence in the model, the best model reclassification was observed when adherence was measured using three or four trajectory groups (NRI = 0.189; 95% confidence interval: [0.171, 0.210]). CONCLUSIONS: Statin adherence trajectory predicted future cardiovascular events better than measures categorizing PDC. Thus, adherence trajectories may be useful for targeting adherence interventions. Copyright (c) 2015 John Wiley & Sons, Ltd.