OP11.01: Interobserver variability in the ultrasound diagnosis of congenital uterine anomalies

Methods: A web-based survey of fellows and trainees of the Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Results: Three hundred and sixty-six (28%) responses included about 50% of Fetal Medicine and Obstetric Ultrasound subspecialists. Just over /4 (76.1%) of practices report or receive reports as a systolic:diastolic ratio (SD), just under 1/3 (31.6%) as pulsatility index (PI) and over 1/3 (36.4%) as resistance index (RI) with 22% declining to nominate a preferred umbilical artery Doppler index. 57% did not know the reference source used in their practice and more than 30% cited unpublished, local reference ranges. Many respondents were well aware of the limitations of umbilical artery Doppler. Survey participants requested 1. consistency 2. gestational age specific reference ranges 3. guidance in interpretation. Conclusions: Regarding Doppler indices, SD remains popular. RI advocates note its straightforward interpretation. PI is favoured by subspecialists, those following international research and those using ratios (e.g. cerebro-placental ratio). Until one index becomes universal, co-reporting of all indices is prudent. Concerning reference chart choice, local, unpublished charts remain popular: their concordance requires investigation. Generally, ideal reference chart are 1. Drawn from a representative population 2. not drawn from a referred population (biased toward abnormality) 3. not subject to retrospective exclusions (biased to ‘‘super-normality’’) 4. Developed using valid statistics, especially to estimate extreme values 5. Use optimal information about gestation 6. Use a good sample size. Ideally usable charts should be subject to peer review and publication, ASUM and RANZCOG endorsement, be readily accessible on ultrasound machines, reporting packages, smart phone applications and the world wide web