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Partin MR, Malone M, Winnett M, Slater J, Bar-Cohen A, Caplan L. The impact of survey nonresponse bias on conclusions drawn from a mammography intervention trial. Journal of clinical epidemiology. 2003 Sep 1; 56(9):867-73.
BACKGROUND AND OBJECTIVE: This study demonstrates the impact of survey nonresponse bias on conclusions from a mammography trial targeting a disadvantaged population. METHODS:The trial randomized 1558 women to three interventions designed to promote repeat mammography: mailed reminder (minimum group); mailed thank-you card, patient newsletters, and reminder (maximum group); and no mailings (control group). The primary outcome, repeat mammogram within 15 months, was assessed from administrative and phone survey data. RESULTS: Administrative estimates revealed a statistically significant difference of 7% between the maximum and control groups on the primary outcome. Survey estimates (response rate 80%) revealed no significant differences. The differences by data source were traced to a survey nonresponse bias. There was a statistically significant difference of 16% between the maximum and control groups among survey nonrespondents for the primary outcome, but there were no differences among survey respondents. CONCLUSION: The findings reiterate that even a low survey nonresponse rate can bias study conclusions and suggest studies targeting disadvantaged populations should avoid relying solely on survey data for outcome analyses.