The efficacy of double reading mammograms in breast screening.

The effect of double reporting the screening mammograms of 31,146 women attending as part of the UK National Health Service Breast Screening Programme was analysed. Ninety per cent had their mammograms read by two of three experienced radiologists. Overall 1846 (5.9%) women were recalled for further assessment. Two hundred and sixty-one patients (0.8%) underwent surgical intervention resulting in the detection of 191 cancers (6.1/1000 women screened). The benign-to-malignant ratio was 1:3.6 (PPV 73.2%). Of the invasive cancers detected 72% had no histological evidence of axillary lymph node metastases. Twenty-one of the 191 cancers detected (10.4%) were missed by one of the two reporters. Six of these were invasive cancers < or = 1 cm in diameter. Comparison of those lesions detected by both readers to those detected by only one, showed readers were more likely to detect those lesions appearing as an opacity (65% vs 38%), but less likely to detect significant microcalcification (15% vs 33%). The difference between the two groups when taken as a whole, however, failed to reach statistical significance (chi 2 = 6.76, d.f. = 3, P = 0.08). In summary, double reporting resulted in an increase in sensitivity of 10%. However, there was a decrease in specificity of 1.8% with 569 women being recalled unnecessarily for assessment and biopsy of 13 benign lesions. The estimated resultant additional financial cost was 13773 pounds.