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.