Randomization at the level of primary care practice: use of pre-intervention data and random effects models

The Anglia menorrhagia education study tests the effectiveness of an educat ion package for the treatment of menorrhagia given to doctors at a primary care level. General practices were randomized to receive or not receive the package. It is hoped that this intervention will reduce the proportion of women suffering from menorrhagia that are referred to hospital. Data are av ailable on the treatment and referral of women in the practices in the educ ation and control groups, both pre- and post-intervention. We define and de monstrate a random effects logistic regression model that includes pre-inte rvention data for calculating the effectiveness of the intervention. Copyri ght (C) 2001 John Wiley & Sons, Ltd.