The detection of intracavitary uterine pathology using off-line analysis of 3-dimensional ultrasound volumes: interobserver agreement and diagnostic accuracy.

Objective To estimate diagnostic accuracy and interobserver agreement in predicting intracavitary uterine pathology at off-line analysis of three-dimensional (3D) ultrasound volumes of the uterus. Methods 3D-volumes (unenhanced ultrasound and gel infusion sonography (GIS) with and without power Doppler, i.e. four volumes per patient) of 75 women presenting with abnormal uterine bleeding at a "Bleeding Clinic" were assessed "off-line" by six examiners. The sonologists were asked to select a tentative diagnosis. A histological diagnosis was obtained by hysteroscopy with biopsy or operative hysteroscopy. Proliferative, secretory or atrophic endometrium were classified as "normal" histology; endometrial polyps, intracavitary myomas, endometrial hyperplasia and endometrial cancer were classified as "abnormal" histology. The diagnostic accuracy of the six sonologists with regard to normal/abnormal histology and the interobserver agreement were estimated. Results Intracavitary pathology was diagnosed at histology in 39% of patients. The agreement between the ultrasound diagnosis and the histological diagnosis (normal versus abnormal) ranged from 67% to 83% for the six sonologists. In 45% of cases all six examiners agreed with regard to the presence/absence of intracavitary pathology. The percentage agreement between any two examiners ranged from 65 to 91% (Cohen's Kappa 0.31 to 0.81). The Schouten kappa [95% CI] for all six examiners was 0.51 [0.40 - 0.62], the highest Schouten Kappa for any three examiners was 0.69. Conclusions The agreement between sonologists with regard to classifying the endometrium/uterine cavity as normal or abnormal as well as the diagnostic accuracy varied substantially. Possible actions to improve interobserver agreement and diagnostic accuracy include optimiziation of image quality and the use of a consistent technique for analysing 3D volumes of the uterus.