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

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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: 33734 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 10000 women screened (95% confidence interval 5 to 13) compared with single reading. A non-consensus double reading policy detected an additional 10 cancers per 10000 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 pounds sterling4853 per 10000 women screened). Non-consensus double reading cost more than single reading (difference pounds sterling19259 per 10000 women screened). Conclusions: In the screening unit studied a consensus double reading policy was more effective and less costly than a single reading policy. Key messages Double reading of screening mammograms detects more cancers than does single reading Double reading with consensus reduces recall rates and has a lower total cost than single reading Breast screening units should consider adopting consensus double reporting for the first screening examination in order to improve efficiency Double reading with consensus is also likely to confer benefits at subsequent screening examinations, though the magnitude and cost effectiveness of these benefits are not known