Garrido-Estepa et al. BMC Cancer 2010, 10:485 http://www.biomedcentral.com/1471-2407/10/485 Table 1 Agreement between the first and second measures using the Wolfe classification Number of mammograms classified in each category in the first and second measurements Second measure First measure N1 P1 P2 N1 12 9 0 P1 4 139 13 P2 0 7 101 DY 0 2 13 Total 16 157 127 Kappa-statistic estimation Agreement Kappa (95% CI) Weighted Kappa (95% CI) Observed % Expected % 82.13 33.02 0.733 (0.674-0.789) 0.835 (0.784-0.876) Low risk categories: N1: Breast composed almost completely of fat, with perhaps just a few fibrous connective tissue strands. P1: Breast composed mainly of fat, although up to a quarter of the sub-areolar area may show beaded or cord-like areas corresponding to prominent ducts. High risk categories: P2: More severe involvement of the breast, with a prominent duct pattern occupying more than one quarter of breast volume. DY: Breast typically contains extensive regions of homogeneous mammographic densities, which appear as sheet-like regions. The proportion of density is greater than that of the fat. patterns from I to V (See table 1 and table 2 for further description of categories). Quantitative based scales, BI-RADS and Boyd, are defined using percentages of density. BI-RADS into quartiles and Boyd divided into six categories of unequal intervals: “A” 0%; “B” > 0-10%; “C” > 10-25%; “D” > 25- 50%; “E” > 50-75% and “F” > 75% (Table 3 and 4). To compare different classification scales having dif- ferent numbers of categories, a dichotomous re-classifi- cation was defined for each scale, grouping different categories into low- and high-risk groups (Table 1, 2, 3 and 4). The Wolfe classification low-risk group was formed by categories N1 and P1 and the high-risk group by categories P2 and DY. For Tabár classification, I-III were considered low-risk and IV-V high-risk. BI- RADS was divided into low-risk (almost entirely fat and scattered fibroglandular densities) and high-risk (hetero- geneously dense and extremely dense). Finally, in the Boyd classification, mammograms classified as A, B, C and D were included in the low-risk group, and E and F categories as high-risk. High/low-risk classifications enabled agreement between the four scales to be compared, using percen- tage agreement and the kappa statistic. Comparison IV 0 16 114 9 139 Page 3 of 8 Total 21 161 122 71 375 Total 21 198 124 32 375 Kappa high/low risk (95% CI) 0.851 (0.798-0.904) DY 0 5 14 56 75 V 0 8 6 15 29 Table 2 Agreement between the first and second measures using the Tabár classification Number of mammograms classified in each category in the first and second measurements Second measure First measure II II 12 III 4 IV 0 V 0 Total 16 Kappa-statistic estimation Agreement Observed % Expected % 82.93 40.05 III 9 170 4 8 191 Kappa (95% CI) Weighted Kappa (95% CI) Kappa high/low risk (95% CI) 0.715 (0.649-0.772) 0.707 (0.623-0.781) 0.800 (0.739-0.861) Low risk categories: I: Mammogram composed of scalloped contours with some lucent areas of fatty replacement and 1 mm evenly distributed nodular densities. II: Mammogram composed almost entirely of lucent areas of fatty replacement and 1-mm evenly distributed nodular densities. III: Prominent ducts in the retroareolar area. High risk categories: IV: Extensive, nodular and linear densities with nodular size larger than normal lobules. V: Homogeneous ground-glass-like appearance with no perceptible features.