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Surveillance of interval cancers (IC) lacks standardisation of review methodologies. We investigated the extent to which 'informed' or 'blinded' review may affect IC classification. This is a retrospective study of 100 validated screening mammograms (20 IC, 80 negative screens) independently reviewed by six radiologists. Three sequenced review methods with increasing information were used: (1) blinded (no IC information, case mix), (2) partially informed, and (3) fully informed. IC 'screening error' (SE) reports averaged 24% (10-40), 33% (20-55), and 42% (35-50) for phases 1, 2, and 3, while 'minimal signs' (MS) reports averaged 6% (5-15), 10% (10-20), and 20% (15-30), respectively. Negative mammograms classification was MS in 18% (7-39) or SE in 19% (11-29), respectively. MS or SE classification was more likely for method 2 (OR=1.78, p=0.033) and method 3 (OR=3.91, p=0.000) relative to method 1, but no reader effect was evident. Inter-observer agreement in classifying at method 1 was slight (k 0.20), lowest (k 0.06) for MS, and fair (k 0.25) for negative and SE categories. More 'informed' review is more likely to yield an IC classification as MS or SE. Due to expected variability, review methods need standardisation to improve screening quality. Our data support blinded review of IC in mammography screening.

We evaluated the role of computer-aided detection (CAD) in cancers undergoing double reading and detected by one reader only. A series of 33 cancers, originally missed by the first reader and detected by the second reader, and 75 negative controls were processed to assess CAD sensitivity, and was read by the six radiologists who originally missed the cancers with the help of CAD printouts. CAD case-based sensitivity, specificity and positive predictive value were 51.5%, 18.6% and 21.7%, respectively. Average sensitivity of all radiologists in all cancers in the series was 74.7%, being higher for CAD+ (86.2%) than for CAD- (62.5%) cancers (P<0.01). When reading cancer cases that they had originally missed, radiologists had a sensitivity of 75.8%, which was higher for CAD+ (100.0%) than for CAD- (58.3%) cancers. The average recall rate was 14.2%, the majority of recalls (45 out of 64) occurring for lesions marked by CAD. CAD may help in detecting at most half of cancers missed at a single reading but detected by a second reader.

The inter- and intraobserver agreement (K statistic) in reporting according to BI-RADS assessment categories was tested on 12 dedicated breast radiologists, with little prior working knowledge of BI-RADS, reading a set of 50 lesions (29 malignant, 21 benign). Intraobserver agreement (four categories: R2, R3, R4, R5) was fair (0.21-0.40), moderate (0.41-0.60), substantial (0.61-0.80) or almost perfect (>0.80) for one, two, five or four radiologists, or (six categories: R2, R3, R4a, R4b, R4c, R5) fair, moderate, substantial or almost perfect for three, three, three or three radiologists, respectively. Interobserver agreement (four categories) was fair, moderate or substantial for three, six, or three radiologists, or (six categories) slight, fair or moderate for one, six, or five radiologists. Major disagreement occurred for intermediate categories (R3=0.12, R4=0.25, R4a=0.08, R4b=0.07, R4c=0.10). We found insufficient intra- and interobserver consistency of breast radiologists in reporting BI-RADS assessment categories. Although training may improve these results, simpler alternative reporting methods (systems), focused on clinical decision-making, should be explored.

The inter- and intraobserver agreement (kappa-statistic) in reporting according to Breast Imaging Reporting and Data System (BI-RADS((R))) breast density categories was tested in 12 dedicated breast radiologists reading a digitized set of 100 two-view mammograms. Average intraobserver agreement was substantial (kappa=0.71, range 0.32-0.88) on a four-grade scale (D1/D2/D3/D4) and almost perfect (kappa=0.81, range 0.62-1.00) on a two-grade scale (D1-2/D3-4). Average interobserver agreement was moderate (kappa=0.54, range 0.02-0.77) on a four-grade scale and substantial (kappa=0.71, range 0.31-0.88) on a two-grade scale. Major disagreement was found for intermediate categories (D2=0.25, D3=0.28). Categorization of breast density according to BI-RADS is feasible and consistency is good within readers and reasonable between readers. Interobserver inconsistency does occur, and checking the adoption of proper criteria through a proficiency test and appropriate training might be useful. As inconsistency is probably due to erroneous perception of classification criteria, standard sets of reference images should be made available for training.