INTEROBSERVER VARIATION IN THE INTERPRETATION OF BREAST IMAGING - COMPARISON OF MAMMOGRAPHY, ULTRASONOGRAPHY, AND BOTH COMBINED IN THE INTERPRETATION OF PALPABLE NONCALCIFIED BREAST MASSES

Purpose: To analyze interobserver agreement in the interpretation of p alpable noncalcified breast masses by means of mammography, ultrasonog raphy, and a combination of both methods. Material and Methods: Mammog rams and ultrasonograms of 100 benign breast masses and 100 malignant ones in 200 patients were retrospectively analyzed by 4 radiologists w ith experience in both imaging modalities. The images were analyzed in dependently and without knowledge of the final diagnosis. The analysis was performed in 3 sessions and used a 5-point rating scale for proba bility of malignancy. The interobserver variation was analyzed by mean s of observed agreement, kappa, and weighted kappa statistics based on the 5-point rating scale and a 3-level scale of the collapsed 5-point scale. The chi-square statistic was used for testing the equality of the kappa values. Results: The overall kappa value on the 3-level scal e was 0.48 (range 0.37-0.61) for ultrasonography, 0.58 (range 0.52-0.6 6) for mammography, and 0.71 (range 0.63-0.79) for the combined readin g. The kappa values were statistically different for ultrasonography b ut did not differ significantly for the mammographic and combined read ings. The combined reading showed higher kappa values than mammography alone, and the improvement was statistically significant for 3 of the 6 pairs of comparison. Conclusion: Radiologists differ substantially in their interpretations of mammograms and breast ultrasonograms. Agre ement was highest in the combined reading, intermediate in mammography , and lowest in ultrasonography.