Centre‐specific ultrasound nuchal translucency medians needed for Down syndrome screening

Abstract

Nuchal translucency (NT) measurements were compared between 13 centres participating in a multi-marker Down syndrome screening program. Results from 4765 women were analysed, and there were highly statistically significant between-centre differences after allowing for gestation (P < 0.0001). Examination of maternal serum marker levels, expressed in multiples of the median (MoM) for gestation, showed that this was not due to gestational errors. Regression analysis was carried out to derive an equation with a centre-specific component that could be used to express NT in MoMs. Use of this equation reduced the variance of logNT by 15% compared to a published equation. The equation can be readily modified for use in other centres.

Quality of nuchal translucency measurements in The Netherlands: a quantitative analysis

“…Additionally, calculation of multiples of the median (MoM) values provides a useful parameter that can be used to assess variation between operators. The median NT‐MoM value should be 1.0 if the NT measurements of a single operator or group of operators do not deviate from the modeled median reference curve13–16. To ensure good quality NT measurements, the accepted median NT‐MoM of an operator should be limited, e.g.…”

Assessment of sonographer nuchal translucency measurement performance – central tendency and dispersion

“…Despite adhering to their guidelines markedly different medians were determined. One approach suggested to correct for differences in median between individuals and centers is the use of center or operator specific medians [15,22]. Such an approach, however, would only be possible for sonographers and centers which performed frequent combined first-trimester NT assessment.…”

“…Firstly, all sonographers assessed performed scans at one single Institution and thus variation in clinical practice between Institutions could not be assessed. Variation between centers has been reported in several studies [7,15]. Secondly, we have adopted an epidemiological approach to the monitoring of NT measurement quality assurance and did not perform a qualitative assessment of images using criteria reported in other studies [7,[24][25][26].…”

“…The SD was then estimated as the difference between the 10th and 90th centiles in the log 10 NTMoM distribution divided by 2.563 [13,15,16]. The center as well as individual sonographers were assessed according to two criteria.…”

Performance adjusted risks: a method to improve the quality of algorithm performance while allowing all to play

“…Some have suggested that there either be individual or at least center‐specific NT medians used to compensate for the variation seen (Logghe et al , 2003; Malone et al , 2005; Palomaki et al , 2009; Wapner et al , 2003). Unfortunately, we have shown decreased performance in such circumstances, and then there is no incentive to improve performance (Evans et al , 2007b).…”