Crown-rump length audit plots with the use of operator-specific PAPP-A and β-hCG median MoM

Audit the crown-rump length (CRL) measurements taken at 11 to 13 weeks scan, using operator-specific median multiples of the median (MoM) for pregnancy-associated plasma protein-A (PAPP-A) and free β-human chorionic gonadotropin (β-hCG) plots, to identify deviations potentially related to a systematic CRL bias.

Study population included consecutive singleton pregnancies undergoing first trimester combined screening, scanned by sonologists with at least 100 scans, during the 2011 to 2012 period. Previously described plots for PAPP-A and β-hCG median MoM points, with their 95% confidence intervals circles, in relation with the expected deviation line were used. These plots have been modified to adjust the deviation line to the sonologist-specific expected MoM variation for each CRL millimetre bias according to each sonologist-specific median gestational ages at both blood sampling and ultrasound.

Twenty-eight sonologists performing 9472 scans were included, accounting for 36% of the 77 sonologists and 70% of the 13 643 scans initially considered. Mean gestational age was 10 + 2 weeks at blood sampling and 12 + 4 weeks at ultrasound. Fifteen sonologists (53%) did not demonstrate any CRL bias, 10 (36%) present with a significant CRL underestimation, being above 2 mm in 6 (21%), and in 3 (11%) the observed deviation could not be explained by a systematic CRL bias.

In sonologists with more than 100 NT measurements, operator-specific PAPP-A and β-hCG median MoM plots are able to identify deviations potentially related to a systematic CRL bias. Systematic underestimation above 2 mm was observed in 1/5 of them. © 2016 John Wiley & Sons, Ltd.