Reliability of manual and semi-automated measurements of nuchal translucency by experienced operators.

Objective: To compare intra-/inter-operator reliability of manual and semi-automated NT measurement by experienced operators.

Methods: Images of 103 fetuses at 11 to 13+6weeks were selected. Two operators performed NT measurement independently 3 times each using both manual and semi-automated methods. Intraoperator reliability of the methods was evaluated using ICCs; interoperator reliability was assessed via correlation between the means of the 3 measurements of each operator. Agreement between the 2 methods was evaluated via Bland-Altman plot.

Results: ICCs for the manual method were 0.80 (95% CI, 0.73-0.85) for operator 1 and 0.82 (95% CI, 0.76-0.87) for operator 2; ICCs for the semi-automated method were 0.80 (95% CI, 0.74-0.85) for operator 1 and 0.82 (95% CI, 0.76-0.86) for operator 2. Interoperator reliability for both methods was high: correlation coefficients 0.91 (95% CI, 0.87-0.94) and 0.96 (95% CI, 0.94-0.97) for manual and semi-automated methods, respectively. Mean NT measured by manual and semi-automated methods was 1.15mm and 1.28mm, respectively (P<0.001). Agreement between the methods was good.

Conclusion: The reliability of semi-automated NT measurements was comparable to that of the manual method. The new method was reproducible and may be used instead of the manual method in the normal range of NT.