Interobserver variability of ultrasound elastography: how it affects the diagnosis of breast lesions.

OBJECTIVE

The purpose of this article is to evaluate the interobserver variability of elastography on real-time ultrasound and how it influences the agreement of final assessment on ultrasound.

SUBJECTS AND METHODS

From April to May 2009, 65 breast lesions of 53 patients (mean age, 42.6 years; range, 18-72 years) who underwent ultrasound-guided core biopsy were included in this study. Ultrasound and elastography images of the lesion subjected to biopsy were obtained and prospectively analyzed by three radiologists with individual real-time image scanning prior to biopsy. Each radiologist recorded final ultrasound BI-RADS assessments using ultrasound and combined ultrasound and elastography and the fat-to-lesion ratio and elasticity score. The histopathologic results obtained from ultrasound-guided core biopsy or excision were used as the reference standard. Diagnostic performances and interobserver agreement were analyzed.

RESULTS

Of the 65 lesions, 43 (66.2%) were benign, and 22 (33.8%) were malignant. Specificity (20.2-33.3%), positive predictive value (38.7-45.1%), and accuracy (46.7-55.4%) were significantly improved in combined ultrasound and elastography (p < 0.001). Area under the curve (AUC) values for all three performers did not show significant differences in ultrasound (AUC, 0.959) and combined ultrasound and elastography (AUC, 0.957) (p = 0.92). Interobserver agreement was not improved with combined ultrasound and elastography (κ = 0.25) in comparison to ultrasound only (κ = 0.37). Interobserver agreement of real-time elastography was fair in both fat-to-lesion ratio (intraclass correlation coefficient score, 0.25) and elasticity score (κ = 0.28). Moderate agreement (κ = 0.46) was seen with static elastography.

CONCLUSION

Elastography improves the specificity, positive predictive value, and accuracy of ultrasound. However, significant interobserver variability exists, with real-time elastographic performance showing fair agreement.