Mammography screening: an incremental cost effectiveness analysis of double versus single reading of mammograms

Abstract

Objective: To compare mammography reading by one radiologist with independent reading by two radiologists.

Design: An observational non-randomised trial at St Margaret's Hospital, Epping.

Subjects: 33 734 consecutive attenders for breast screening in the main trial and a sample of 132 attenders for assessment who provided data on private costs.

Interventions: Three reporting policies were compared: single reading, consensus double reading, and non-consensus double reading.

Main outcome measures: Numbers of cancers detected, recall rates, screening and assessment costs, and cost effectiveness ratios.

Results: A policy of double reading followed by consensus detected an additional nine cancers per 10 000 women screened (95% confidence interval 5 to 13) compared with single reading. A non-consensus double reading policy detected an additional 10 cancers per 10 000 women screened (95% confidence interval 6 to 14). The difference in numbers of cancers detected between the consensus and non-consensus double reading policies was not significant (95% confidence interval -0.2 to 2.2). The proportion of women recalled for assessment after consensus double reading was significantly lower than after single reading (difference 2.7%; 95% confidence interval 2.4% to 3.0%). The recall rate with the non-consensus policy was significantly higher than with single reading (difference 3.0%; 2.5% to 3.5%). Consensus double reading cost less than single reading (saving 4853 pounds per 10 000 women screened). Non-consensus double reading cost more than single reading (difference 19 259 pounds per 10 000 women screened).

Conclusions: In the screening unit studied a consensus double reading policy was more effective and less costly than a single reading policy.