Sixteen RCTs including 8401 intervention participants and 7957 control participants.
Reminder vs no reminder:
US studies (n=11) - Women who received reminders were significantly more likely to attend than those who did not (OR=1.48, P<0.001).
Non-US studies (n=2) - Women who received reminders were significantly more likely to attend than those who did not (OR=5.57, P<0.001).
Tailored reminder vs generic reminder:
US studies (n=3) - Women receiving tailored reminders were significantly more likely to attend than those who received generic reminders (OR=1.87, P<0.05).
Non-US studies (n=2) - Studies outside the US were not pooled as the Woolf test indicated significant differences between the studies. In general however, the studies found that reminders with appointment times were more effective.
Other factors associated with screening:
Reporting of other factors associated with screening attendance were inconsistent and in the majority of cases there was insufficient data to determine which factors were important. However, variables related to perceived health risk including health status, family history and previous mammography appeared to be associated with screening.
Sensitivity analyses:
Sequentially removing each study indicated that four studies changed the OR by more than 10%. The most influential of the studies had a large sample size and when removed the OR for studies conducted outside the US changed from 4.08 to 1.68. However, the effect still remained statistically significant (P<0.05), as was the case with the removal of any of the studies.