title: Accessing data from external centralized sources to enhance analysis of a completed clinical trial.
abstract: After the data collection phase of a clinical trial has been completed, new hypotheses may surface which require additional data before they can be tested. In the Veterans Affairs Cooperative Study on Single Drug Therapy of Hypertension, we investigated the relationship between location of the participating center, race and ability to control blood pressure. The analysis indicated poorer blood pressure control among sites located in the "stroke belt" (southeastern United States), especially among African-Americans. We sought to determine whether the effect was attributable to socioeconomic patterns; however, income data were not collected as part of the original study. Therefore, we accessed centralized data bases to obtain zipcode-level income information for the randomized study patients. This approach yielded estimates of income data for 94.3% of the patients and compared favorably to data acquisition rates for variables which were collected prospectively in the study.
authors.affiliation: Department of Veterans Affairs Cooperative Studies Program Coordinating Center, Hines VA Hospital, Illinois, USA.
authors.forename: M
authors.initials: M
authors.lastname: Abdellatif
authors.forename: D J
authors.initials: DJ
authors.lastname: Reda
authors.forename: D
authors.initials: D
authors.lastname: Williams
authors.forename: W C
authors.initials: WC
authors.lastname: Cushman
authors.forename: B J
authors.initials: BJ
authors.lastname: Materson
mesh_terms: D000959:Antihypertensive Agents / Q000627:therapeutic use; D044383:Black People; D001794:Blood Pressure / Q000187:drug effects; D016009:Chi-Square Distribution; D003625:Data Collection; D019992:Databases as Topic; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000188:drug therapy; D007182:Income; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012111:Residence Characteristics; D012959:Socioeconomic Factors; D015144:Southeastern United States; D020521:Stroke / Q000209:etiology; D044465:White People; D001741:Black or African American
chemical_list: D000959:Antihypertensive Agents