The prediction of pouch of Douglas obliteration using offline analysis of the transvaginal ultrasound 'sliding sign' technique: inter- and intra-observer reproducibility

Abstract

study question: What is the inter-/intra-observer agreement and diagnostic accuracy among gynaecological and non-gynaecological ultrasound specialists in the prediction of pouch of Douglas (POD) obliteration (secondary to endometriosis) at offline analysis of two-dimensional videos using the dynamic real-time transvaginal ultrasound (TVS) ‘sliding sign’ technique? summary answer: The inter-/intra-observer agreement and diagnostic accuracy for the interpretation of the TVS ‘sliding sign’ in the prediction of POD obliteration was found to be very acceptable, ranging from substantial to almost perfect agreement for the observers who specialized in gynaecological ultrasound. what is known already: Women with POD obliteration at laparoscopy are at an increased risk of bowel endometriosis; therefore, the pre-operative diagnosis of POD obliteration is important in the surgical planning for these women. Previous studies have used TVS to predict POD obliteration prior to laparoscopy, with a sensitivity of 72 –83% and specificity of 97 –100%. However, there have not been any reproducibility studies performed to validate the use of TVS in the prediction of POD obliteration pre-operatively. study design, size, duration: This was a reproducibility study which involved the offline viewing of pre-recorded video sets of 30 women presenting with chronic pelvic pain, in order to determine POD obliteration using the TVS ‘sliding sign’ technique. The videos were selected on real-time representative quality/quantity; they were not obtained from sequential patients. There were a total of six observers, including four gynaecological ultrasound specialists and two fetal medicine specialists. The study was conducted over a period of 1 month (March 2012–April 2012). participants/materials, setting, methods: The four gynaecological ultrasound observers performed daily gynaecological scanning, while the other two observers were primarily fetal medicine sonologists. Each sonologist viewed the TVS ‘sliding sign’ video in two anatomical locations (retro-cervix and posterior uterine fundus), i.e. 60 videos in total. The POD was deemed not obliterated, if ‘sliding sign’ was positive in both anatomical locations (i.e. anterior rectum/rectosigmoid glided smoothly across the retro-cervix/posterior fundus, respectively). If the ‘sliding sign’ was negative (i.e. anterior rectum/rectosigmoid did not glide smoothly over retro-cervix/posterior fundal region, respectively), the POD was deemed obliterated. Diagnostic accuracy and inter-observer agreement among the six sonologists was evaluated. The same sonologist was also asked to reanalyse the same videos, albeit in a different order, at least 7 days later to assess for intra-observer agreement. A separate analysis of the inter- and intra-observer correlation was also performed to determine the agreement among the four observers who specialized in gynaecological ultrasound. Cohen’s k coefficient ,0 meant that there was poor agreement, 0.01 –0.20 slight agreement, 0.21– 0.40 fair agreement, 0.41 –0.60 moderate agreement, 0.61 –0.80 substantial agreement and 0.81 –0.99 almost perfect agreement.