The CUSUM test applied in prospective nuchal translucency quality review

Abstract

To design a cumulative sum (CUSUM) test for prospective nuchal translucency (NT) measurement quality review that is as stringent as the retrospective quality review methods based on distribution parameters currently in use. The database including all fetal NT measurements obtained during a 2-year period in a single center was reviewed, and measurements obtained by sonologists who measured fewer than 100 cases were excluded. The NT distribution parameters proposed by The Fetal Medicine Foundation (FMF) and the Women & Infants Hospital of Rhode Island (WIHRI) were assessed in the whole NT series and in sonologist-specific distributions. A previously described CUSUM model was adapted to fulfil our objective. Two thousand four hundred and seventy-five NT measurements were obtained by seven sonologists during the study period (January 2007-December 2008). In the assessment of sonologist-specific NT distributions, two sonologists fulfilled all the FMF and WIHRI criteria, one showed NT overestimation and four failed due to NT underestimation. Our new CUSUM test model, based on multiples of the median deviations, showed good agreement with the FMF and WIHRI methods in the assessment of sonologist-specific performance. Our CUSUM test model showed close agreement with the retrospective quality review methods based on distribution parameters currently in use, but with the advantage that it can be applied prospectively, allowing for earlier correction of deviations from target performance.