Intra- and interoperator repeatability of the nuchal translucency measurement

Objective The aim of this study was to assess the repeatability of nuchal t ranslucency measurement by well-trained sonographers either experienced or Inexperienced with the measurement. Methods The nuchal translucency was measured three times by two out of nine operators in 161 pregnant women attending two teaching hospitals. Intra-op erator and inter-operator variation rc,as assessed by calculating the stand ard deviation (SD). Intraclass Correlation Coefficients (ICC) with a 95% lo wer confidence limit (95% CL) were calculated for each operator and for pai rs of operators. Intra-and inter-operator kappa statistics were calculated after dichotomising the results into a nuchal translucency smaller or large r than 3 mm. Results The SD of intra-operator difference was 0.35 mm. The intra-operator repeatability, showed ICCs varying from 0.83 to 0.95 for the experienced o perators and from 0.47 to 0.83 for the inexperienced. The SD of inter-opera tor differences was 0.56 mm, 0.46 mm and 0.44 mm, based on one, two and thr ee measurements, respectively. The inter-operator repeatability, showed a v ariation in ICC from 0.74 to 0.95 in pairs of experienced sonographers to 0 .51 in one pair inexperienced with the measurement. The kappa value express ing the intra and inter-operator repeatability as being > 3 mm or < 3 mm wa s 0.88 and 0.85, respectively Conclusion This study supports the finding that the nuchal translucency mea surement is reproducible, as long as it is performed by sonographers well t rained in the technique of this measurement.