OP15.05: Development and validation of a preoperative ultrasound staging system for predicting level of laparoscopic endometriosis surgery required

To develop and validate a preoperative ultrasound based staging system to predict laparoscopic level required for endometriosis surgery. Multicentre study of consecutive women presenting with chronic pelvic pain from January 2009 to March 2015. All women with symptoms of chronic pelvic pain +/− history of endometriosis underwent a detailed specialised transvaginal ultrasound (TVS) in a tertiary referral unit to stage the endometriosis prior to laparoscopy. Two ultrasound staging systems (SS1 and SS2) were compared and correlated with the laparoscopic skill levels required (levels I - III as recommended by the Royal College of Obstetrics and Gynecology). 200/267 were used as the training set to develop the staging system. Bootstrapping validation was performed on the total dataset of 267. 267/274 (94%) women with pre-operative TVS and laparoscopic outcomes were included in the final analysis. The rate of correctly predicting the exact level of skills needed using SS1 and SS2 were 75.7% and 81.6% respectively. Cohen's kappa agreement between SS1 and SS2 and levels of training required at surgery were 0.627 and 0.717, respectively. SS2 outperformed SS1 both in the training set and bootstrap validation. The sensitivity, specificity, positive predictive and negative predictive values for predicting the need for laparoscopic skill levels of I, II and III for SS1 was 81.8/89.0/85.9/85.6, 71.5/78.9/54.4/89.9 and 69.9/96.7/90.6/87.7 percent, respectively and for SS2 81.8/89.0/85.9/85.6, 71.5/87.8/64.6/90.8 and 89.1/95.6/90.2/95.1 percent, respectively. We have generated and validated a pre-operative ultrasound staging tool to triage women to the most appropriate level of laparoscopic endometriosis surgery. This staging system needs to be externally validated in order to assess its general applicability in other centres.