Mapping geographic areas of high and low drug adherence in patients prescribed continuing treatment for acute coronary syndrome after discharge.

UNLABELLED ABSTRACT STUDY OBJECTIVE: To determine the feasibility of using geographic information system (GIS) technology to identify geographic areas of high and low adherence to cardiovascular drug therapy for treatment of acute coronary syndrome (ACS) in patients discharged from a university-affiliated hospital. Design. Retrospective analysis. DATA SOURCE A registry of patients admitted to and discharged from a large university-affiliated medical center for the treatment of ACS. Patients. A total of 1081 adults distributed over 300 census tracts who were discharged between April 1999 and December 2004 with a diagnosis of an ACS event of unstable angina or acute myocardial infarction. MEASUREMENTS AND MAIN RESULTS Data were collected on patient demographics, home addresses, and adherence to four classes of drugs - statins, angiotensin-converting enzyme inhibitors, β-blockers, and aspirin - at 6-12 months after discharge for the ACS index event. A GIS program was used to map patient addresses and adherence data to geographic coordinates. Hot Spot Analysis was used to determine the existence of any spatial clustering patterns in adherence rates. The analysis was performed at the census tract level by using the percentage of nonadherent patients within a census tract to represent adherence for the people living within that tract, standardized by the number of residents in a census tract aged 40 years or older. Hot Spot Analysis identified unique geographic areas of high, neutral, and low adherence in the southeast area. Highly adherent census tracts were primarily located in and around the city where the university hospital and clinics are located. Areas of low adherence were located to the west, southwest, and southeast of the city. All other census tracts were considered neutral in adherence rates. CONCLUSION Mapping geographic areas of drug adherence is feasible with use of GIS technology, with spatial mapping able to detect areas of varying levels of adherence. Future research should examine local-level factors associated with low adherence, which can be used to derive tailored, locally relevant interventions to improve long-term drug adherence.