Authors' response

Extract

We thank Bulliard and Levi for their interest in our international population-based survey of women's perception of the benefits of mammography screening.^1,2 Our survey showed that in the US and three European countries (UK, Italy, Switzerland) a high proportion of women overestimated the benefits that can be expected from screening mammography.

Bulliard and Levi argue that the questions used in our survey could not adequately measure perceptions and that simpler, open-ended questions should have been used. Survey questions can always be improved, particularly in the light of answers received, but we do not think that the use of open-ended questions would have led to different conclusions. For example, even when classifying the answer that biannual screening in women older than 50 years reduces breast cancer mortality ‘by about half’ as correct, 20% (Switzerland) to 38% (US) of women would overestimate benefits (Table 1 in ref. 2). These findings are in line with the results of a survey in the Canton of Geneva conducted in 1998.³