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Quality assessment in prospective nuchal translucency screening for Down syndrome in the Copenhagen first trimester study
Author(s) -
Wojdemann K.,
Christiansen M.,
Sundberg K.,
Shalmi A.C.,
Tabor A.
Publication year - 2001
Publication title -
ultrasound in obstetrics and gynecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.202
H-Index - 141
eISSN - 1469-0705
pISSN - 0960-7692
DOI - 10.1046/j.1469-0705.2001.abs17-8.x
Subject(s) - medicine , sonographer , kappa , nuchal translucency , cohen's kappa , prospective cohort study , magnification , certification , standard deviation , nuchal translucency measurement , obstetrics , first trimester , ultrasound , pregnancy , fetus , statistics , radiology , surgery , artificial intelligence , philosophy , linguistics , genetics , mathematics , biology , computer science , political science , law
Purpose: To develop and apply a quality control system in a Down syndrome (DS) screening study using nuchal translucency (NT) as interventional marker. Methods: In a prospective DS screening study, the NT was measured in 9236 pregnancies. For quality assessment two models were introduced: (I) image‐scoring evaluation of the NT measurements and (II) establishment of the distribution of NT multiple of the medians (MoMs) over time and influence of an intervention. Results: The observer variability in the image‐scoring evaluation was high with a kappa value of 0.48 in the overall validation. A revised model showed better interobserver agreement with a kappa value of 0.58; regarding the single criteria the differences were however, still unsatisfactory, i.e. we found highly significant differences for the criteria ‘position of the fetus’ ( P = 0.0026) and ‘magnification of the image’ ( P = 0.0001). Regarding the distribution of the NT MoMs, the median NT MoM (in groups of 50 fetuses each) stabilized after a short learning phase (representing the practical part of the sonographer's certification). The intergroup standard deviation decreased from initial 0.100–0.060 after the learning phase, and 0.046 after the intervention. Conclusions: When well‐trained certified examiners perform NT screening, continuous evaluation of the distribution of the NT MoM seems to be a good method to assess the quality for a center and may also be used to identify individual examiners deviating from the mean performance. Intervention towards the examiners seems to decrease variation, which should theoretically decrease the false positive rate. The image‐scoring methods we introduced cannot be recommended for quality control in an NT screening program.