Interobserver Variability of Sonography for Prediction of Placenta Accreta

Objectives-The sensitivity of sonography to predict accreta has been reported as higher than 90%. However, most studies are from single expert investigators. Our objective was to analyze interobserver variability of sonography for prediction of placenta accreta. Methods-Patients with previa with and without accreta were ascertained, and images with placental views were collected, deidentified, and placed in random sequence. Three radiologists and 3 maternal-fetal medicine specialists interpreted each study for the presence of accreta and specific findings reported to be associated with its diagnosis. Investigator-specific sensitivity, specificity, and accuracy were calculated. K statistics were used to assess variability between individuals and types of investigators. Results-A total of 229 sonographic studies from SS patients with accreta and 56 control patients were examined. Accuracy ranged from 55.9% to 76.4%. Of imaging studies yielding diagnoses, sensitivity ranged from 53.4% to 74.4%, and specificity ranged from 70.8% to 94.8%. Overall interobserver agreement was moderate (mean kappa +/- SD = 0.47 +/- 0.12). K values between pairs of investigators ranged from 0.32 (fair agreement) to 0.73 (substantial agreement). Average individual agreement ranged from fair (kappa = 0.35) to moderate (kappa = 0.53). Conclusions-Blinded from clinical data, sonography has significant interobserver variability for the diagnosis of placenta accreta.