Comparisons of the diagnostic accuracy of the ultrasonic sign-score method and MRI for PA, PI and PP in high-risk gravid women: a retrospective study

BACKGROUND: The diagnosis and management of placenta accrete spectrum (PAS) is a great challenge to obstetricians. Ultrasound (US) and magnetic resonance imaging (MRI) are two main methods to detect PAS. MRI has high resolution, but the examination fee is expensive. US machine and examination fee is cheap, but the resolution is relatively low. Balancing the cost and accuracy for PAS diagnosis is very important. METHODS: The ultrasonic sign-score method and MRI findings for 49 pregnant women at high risk of placental implantation were retrospectively analyzed. Inclusion criteria: (I) at high risk for PA as described in the Guidelines to Placenta Accreta Spectrum Disorders issued by the American College of Obstetricians and Gynecologists (ACOG) in 2018; (II) complete records of ultrasonic sign-scoring method and MRI data; (III) cesarean section; (IV) definite surgical and/or pathological findings. The results were validated by the gold-standard surgical or postoperative pathological findings, and the efficacy of the 2 imaging approaches in diagnosing placenta PAS was compared. Kappa test was used to analyze the consistency. Receiver operating characteristic (ROC) curves were used to compare the sensitivity and specificity. RESULTS: The mean maternal age was 32.6±4.4 years. The mean gestational week was 35.9±2.0 weeks. The mean gravidity was 3.3±1.1. The surgical or histopathological findings revealed PA in 26, placenta increta (PI) in 19 and placenta percreta (PP) in 4 of the 49 women. The diagnosis accuracy of PA, PI, and PP was higher using the ultrasonic sign-scoring method than MRI (75.51%, 73.47%, and 97.96% vs. 61.22%, 57.14% and 91.84%, respectively). The areas under the ROC curve for the sensitivity and specificity of the ultrasonic sign-scoring method and MRI in the diagnosis of PA, PI, and PP were 0.757 [95% confidence interval (CI): 0.613, 0.868], 0.725 (95% CI: 0.579, 0.843), 0.989 (95% CI: 0.907, 1.000), and 0.607 (95% CI: 0.457, 0.743), 0.544 (95% CI: 0.395, 0.687), 0.614 (95% CI: 0.464, 0.749), respectively. CONCLUSIONS: Although the sensitivity and specificity were lower than 0.8, the ultrasonic sign-scoring method was still superior to MRI in the detection of PI and PP. US can be used to help identify high-risk gravid women.