Background: Various interventions to promote repeat use of mammography have been evaluated, but the efficacy of such interventions is not well understood.
Methods: We searched electronic databases through August 15, 2009, and extracted data to calculate unadjusted effect estimates (odds ratios [ORs] and 95% confidence intervals [CIs]). Eligible studies were those that reported estimates of repeat screening for intervention and control groups. We tested homogeneity and computed summary odds ratios. To explore possible causes of heterogeneity, we performed stratified analyses, examined meta-regression models for 15 a priori explanatory variables, and conducted influence analyses. We used funnel plots and asymmetry tests to assess publication bias. Statistical tests were two-sided.
Results: The 25 eligible studies (27 effect estimates) were statistically significantly heterogeneous (Q = 69.5, I(2) = 63%, P < .001). Although there were homogeneous subgroups in some categories of the 15 explanatory variables, heterogeneity persisted after stratification. For all but one explanatory variable, subgroup summary odds ratios were similar with overlapping confidence intervals. The summary odds ratio for the eight heterogeneous reminder-only studies was the largest observed (OR = 1.79, 95% CI = 1.41 to 2.29) and was statistically significantly greater than the summary odds ratio (P(diff) = .008) for the homogeneous group of 17 studies that used the more intensive strategies of education/motivation or counseling (OR = 1.27, 95% CI = 1.17 to 1.37). However, reminder-only studies remained statistically significantly heterogeneous, whereas the studies classified as education/motivation or counseling were homogeneous. Similarly, in meta-regression modeling, the only statistically significant predictor of the intervention effect size was intervention strategy (reminder-only vs the other two combined as the referent). Publication bias was not apparent.
Conclusions: The observed heterogeneity precludes a summary effect estimate. We also cannot conclude that reminder-only intervention strategies are more effective than alternate strategies. Additional studies are needed to identify methods or strategies that could increase repeat mammography.