Delivery of preventive health services for breast cancer control: a longitudinal view of a randomized controlled trial.

OBJECTIVE:

To develop a longitudinal model to characterize the delivery of mammography services using repeated observations of mammography referral rates during a randomized controlled trial (RCT) of physician mammography reminders.

DATA SOURCES/STUDY SETTING:

Administrative records of a health department and observational data on mammography appointment scheduling.

STUDY DESIGN:

The design was a longitudinal study of month-specific referral rates during a 1-year RCT. A retrospective case-control study was used to investigate differences between women with timely and delayed (or absent) mammography referral assessed at the end of the intervention year.

DATA COLLECTION/EXTRACTION METHODS:

Month-specific indicators for referrals and missed clinical opportunities, that is, months when clinic visitors were due for a mammogram and not referred, were constructed using administrative and observational data.

FINDINGS:

In the unadjusted analysis, the effectiveness of the reminder declined over time. However, in a multivariate analysis that controlled for the number of missed opportunities, the effectiveness was constant over time. On a monthly basis, physician reminders were significantly associated with higher referral rates among clinic visitors newly due for mammography (adjusted OR = 2.8, 95 percent CI = 1.3, 5.8) or who had one previously missed clinical opportunity (adjusted OR = 3.0, 95 percent CI = 1.6, 5.3) but were not for those with two or more missed clinical opportunities (adjusted OR = 1.2, 95 percent CI = 0.7, 2.3). Factors independently associated with delayed referral were age over 65, presence of more than one chronic illness, and the absence of a physician mammography reminder.

CONCLUSIONS:

Longitudinal models that examine rates of referral over time and include information about outcomes on previous visits can enhance our understanding of how intervention strategies work in practice.