Randomized controlled trial of a repeat mammography intervention: effect of adherence definitions on results

As overall mammography rates approach national goals, mammography promotion efforts must increasingly focus on repeat adherence. This randomized controlled trial examined the effect of two interventions on repeat mammography utilization using various adherence definitions.

1,558 women aged 40-63 receiving a mammogram through a federally funded screening program were randomized to three groups: mailed reminder (minimum group); mailed thank you card, newsletters, and reminder (maximum group); no mailings (control). The primary outcome (repeat mammogram) was assessed 13, 15, 18, and 24 months after the qualifying mammogram using administrative data.

The proportions receiving a repeat mammogram within 13 months were 0.28, 0.30, and 0.32 for control, minimum, and maximum groups, respectively. The corresponding proportions were 0.38, 0.43, and 0.45 at 15 months; 0.43, 0.49, and 0.51 at 18 months; and 0.47, 0.52, and 0.54 at 24 months. There were no significant differences across study groups at 13 months. The differences between control and maximum subjects at 15, 18, and 24 months were statistically significant. The differences between control and minimum subjects were significant only at 18 months.

The two low-cost mailed interventions evaluated modestly increased repeat mammography utilization. However, effects were not visible until at least 15 months after the qualifying mammogram.