Methodological issues in mammography double reading studies

Objectives An examination of the methods used in assessing cancer detection rates in double reading studies to obtain a clear interpretation of the disparate results from differing studies. Setting National breast screening programmes. Methods Critical appraisal of methodologies used in the comparison of cancer detection rates with single or double reading. Results The reported improvement in cancer detection rate with double reading varies greatly between studies, depending upon whether the study is blinded and the statistic used. A method of calculating the increase in cancer detection rate due to a second reader is proposed.