INTEROBSERVER VARIABILITY OF MIDTRIMESTER FETAL NUCHAL THICKNESS

Objective: To assess the interobserver variability of ultrasound measu red fetal nuchal thickness (NT). Study design: NT was measured in 103 consecutive early midtrimester pregnancies (13-18 weeks) by three ultr asonographists with different levels of expertise, in our Prenatal Dia gnosis Unit. Measurements were obtained prior to amniocentesis, blindl y in relation to other examiners' values. The Lin's concordance correl ation coefficient and the Kappa statistics were used to assess concord ance between observed values. Results: Mean differences between pairs of observers ranged from 0.44 to 0.57 mm. A higher concordance correla tion between measurements was obtained between the more experienced ob servers (r=0.77 versus r=0.51). When assigning cases with a NT greater than or equal to 5 mm to a group at risk for Down's syndrome, a high concordance between experienced ultrasonographists was observed (98% a greement; kappa = 0.90). Conclusion: Interobserver variability in NT w as acceptable between experienced ultrasonographists. (C) 1997 Elsevie r Science Ireland Ltd.