Effect of false-positive screening mammograms on rescreening in Western Australia

To the Editor: In their recent article on false-positive screening mammograms and their effect on rescreening rates within the BreastScreen WA (BSWA) program, Sim and colleagues posit that an absolute reduction in future rescreening of 3 percentage points can be seen among women who are recalled for assessment but do not have breast cancer.1

The analysis presented did not adjust for other factors known to influence rescreening rates. The authors acknowledge that rescreening rates varied between the initial screening round and subsequent screening rounds but failed to include this in a multivariate analysis.

Reported rescreening rates within the analysis were 62.4% for all women screened in the initial round and 72.5% for women screened in a second or subsequent round.

When the effect of a false-positive result was reported by screening round, the absolute difference was much lower for both first screens (1.5 percentage points) and subsequent screens (1.0 percentage points).

The data presented showed that 37% of women who had a false-positive screening result were undergoing their first screening mammogram through the BSWA program and that only 18% of women with a true-negative result were participating for the first time. There are many reasons why false-positive results should be minimised within any screening program; however, because of the overrepresentation of women undergoing a first screen in the false-positive group, these data overstate the true effect of false positives on the rescreening rate.