Assessing quality standards in measurement of uterine artery pulsatility index at 11 to 13 + 6 weeks' gestation

Objectives: To assess the effect of audit and feedback on the performance of first-trimester uterine artery pulsatility index (UtA-PI) measurement, to determine whether operator experience affects performance and whether an operator's measurement profile affects the screen-positive rate for early-onset pre-eclampsia (PE).

Methods: This was a prospective cohort study in which UtA-PI measurements were collected between 11 to 13 + 6 weeks' gestation by 12 operators and were entered into individualized calculators to convert them to multiples of a locally-derived median (MoM). Individual sonographer cumulative sum (CUSUM) and target charts were generated to assess central tendency and dispersion to identify systematic measurement errors and deviation from expected measurement performance. Six of the operators received regular feedback whilst the remaining six received no feedback. Each group consisted of four experienced operators and two relatively inexperienced operators. The average MoM for each operator was compared with their respective screen-positive rates for early-onset PE.

Results: The group that received feedback performed better than that which received none, with results more closely matching the expected measurement distribution. UtA-PI measurements were comparable between the experienced and inexperienced sonographers (mean log10 lowest PI MoM, -0.0089 vs 0.0124, respectively); however the inexperienced sonographers had a higher overall screen-positive rate for early-onset PE (10.0% vs 2.7%, respectively). There was a significant positive correlation between the mean MoM for each operator and the screen-positive rate (r = 0.63).

Conclusions: CUSUM and target graphs are an effective method of audit for first-trimester UtA-PI measurement. Feedback to operators resulted in improved measurement performance, which will ultimately result in improved screening accuracy for PE.