Nuchal translucency measurement: are qualitative and quantitative quality control processes related?

OBJECTIVES: Two types of quality assurance processes for nuchal translucency (NT) measurement have been described: qualitative through review of images and quantitative comparison of operator's specific NT distribution to reference distributions. The aim of this study was to assess the results of these two approaches. METHODS: Prospective evaluation of sonologists affiliated to the French Ultrasound College who first underwent qualitative evaluation based on the College Français d'Echographie Foetale (CFEF) score. During one year, those same sonologists measured the NT for Down syndrome screening purposes. The operator's specific NT distributions were compared to their CFEF score, their number of unsatisfactory images and their number of NT measurements per year. RESULTS: The study involved 1726 sonologists who performed 174 722 first-trimester examinations. Mean (SD) quantitative score was 23.4/32 (+/-7.4). The median [inter-quantile range] number of examinations per sonologist was 69 [37; 123]. The median [range] NT multiples of the mean (MoM) value was 0.81 [0.46; 1.22]. NT (MoM) absolute deviation from 1 MoM was significantly correlated with mean score obtained (R(2) = -0.17, p < 0.0001), number of unacceptable images (R(2) = 0.14, p < 0.0001) and number of ultrasound scans performed per year (R(2) = -0.19, p < 0.0001). CONCLUSION: Our results suggest that both processes are clearly related.

Screening for Down syndrome using first-trimester combined screening followed by second-trimester ultrasound examination in an unselected population.

OBJECTIVE: Recent studies have reported the efficacy of first-trimester combined screening for Down syndrome based on maternal age, serum markers (human chorionic gonadotropin, pregnancy-associated plasma protein A), and ultrasound measurement of fetal nuchal translucency. However, those do not incorporate the value of the widely accepted routine 20-22 weeks' anomaly scan. STUDY DESIGN: We carried out a multicenter, interventional study in the unselected population of a single health authority in order to assess the performance of first-trimester combined screening, followed by routine second trimester ultrasound examination and/or screening by maternal serum markers (free beta-hCG and alpha-fetoprotein measurement or total hCG, alpha-fetoprotein, and unconjugated estriol measurement) when incidentally performed. Detection and screen positive rates were estimated using a correction method for nonverified issues. A cost analysis was also performed. RESULTS: During the study period, 14,934 women were included. Fifty-one cases of Down syndrome were observed, giving a prevalence of 3.4 per 1000 pregnancies. Of these, 46 were diagnosed through first (n = 41) or second (n = 5) trimester screening. Among the 5 screen-negative Down syndrome cases, all were diagnosed postnatally after an uneventful pregnancy. Detection and screen positive rates of first-trimester combined screening were 79.6% and 2.7%, respectively. These features reached 89.7%, and 4.2%, respectively, when combined with second-trimester ultrasound screening. The average cost of the full screening procedure was 108 euros (120 dollars) per woman and the cost per diagnosed Down syndrome pregnancy was 7,118 euros (7909 dollars). CONCLUSION: Our findings suggest that 1 pragmatic interventional 2-step approach using first-trimester combined screening followed by second-trimester detailed ultrasound examination is a suitable and acceptable option for Down syndrome screening in pregnancy.