Quality assessment of routine nuchal translucency measurements: a North American laboratory perspective

To assess nuchal translucency measurements that were performed as part of routine prenatal screening for Down syndrome.

Collect ultrasound measurements of nuchal translucency and crown rump length provided by individual sonographers over a 6-month period to six North American prenatal screening laboratories, along with the laboratory's nuchal translucency interpretation in multiples of the median. For sonographers with 50 or more observations, compute three nuchal translucency quality measures (medians, standard deviations, and slopes), based on epidemiological monitoring.

Altogether, 23,462 nuchal translucency measurements were submitted by 850 sonographers. Among the 140 sonographers (16%) who submitted more than 50 observations, 76 (54%) were found to have all three quality measures in the target range. These 140 sonographers collectively accounted for 14,210 nuchal translucency measurements (61%). The most common single measure to be out of range was nuchal translucency multiples of the median, found for 29 of the 140 sonographers (21%).

Laboratories should routinely monitor the quality of nuchal translucency measurements that are received for incorporation into Down syndrome screening risk calculations and interpretations. When possible, instituting sonographer-specific medians and providing individualized feedback about performance and numbers of women tested offer the potential to yield more consistent and improved performance.