A randomized design for repeated binary outcomes used to evaluate continued effectiveness of a breast cancer control intervention strategy

The Literature has not discussed in detail design and evaluation strategies for the assessment of continued effectiveness of intervention strategies. In this article we present an approach to evaluating continued effectivenes s with two repeated binary outcomes that are related to the use of preventi ve sen ices. We present a two-stage design with independent randomization p rocedures for each of two successive controlled trials and discuss the impl ications of the randomization plan for the statistical evaluation. Interven tion effectiveness for each year is determined by an adjusted odds ratio th at compares the odds of procedure use for those who received the interventi on to those who did not. Changes in the two adjusted odds ratios between su ccessive years are assessed within the context of a regressive logistic mod el. We demonstrate these methods by applying them to the Metropolitan Detro it Project to Reduce Avoidable Mortality from Breast Cancer. In this projec t, computer-generated physician mammography reminders placed prominently in medical records were used to promote mammography referrals among women vis iting primary care clinics during a 2-year intervention period. An assessme nt of the change in intervention effectiveness as well as an adjusted estim ate of the overall intervention effectiveness for the 2 years were obtained from a multivariate regressive logistic model, The advantage of this appro ach was its potential for reducing bias and producing a balanced comparison between intervention groups during the second year of intervention. This i ssue was important because previous work indicated that having had a mammog ram had a significant impact on subsequent mammography use. An important co mponent in the implementation of this design was an information management system that facilitated doing two randomization procedures efficiently. As information and computer technology advance, and as more sophisticated info rmation systems are used for data management, designs such as these become reasonable alternatives to consider. Control Clin Trials 1999;203280-293 (C ) Elsevier Science Inc. 1999.