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24: Inter-rater agreement of qualitative grading for fetal echocardiographic findings in twin-twin transfusion syndrome (TTTS)

      Objective

      Several TTTS staging systems have been described which grade severity of recipient twin (RT) cardiomyopathy by echocardiography, but require either quantitation of Doppler myocardial performance index (MPI), or are relatively complex. We sought to determine if qualitative assessment utilizing only the 4 chamber cardiac view could discriminate severity of RT cardiomyopathy in TTTS.

      Study Design

      The Cincinnati Staging system assesses severity of cardiac dysfunction by grading ventricular hypertrophy, AV (atrioventricular) valve regurgitation, cardiomegaly, systolic dysfunction and MPI. We retrospectively reviewed 100 fetal echocardiograms divided into 4 equal cohorts by Cincinnati stage (none, IIIA, IIIb, IIIc). Six fetal care providers (2 surgeons, 3 MFMs, 1 radiologist) blinded to Cincinnati Stage scored each of the above variables–except MPI–in addition to scoring overall impression of cardiomyopathy severity. Each variable was scored as normal, mild or moderate/severe based on the standard 4 chamber view with color flow Doppler imaging. Inter-rater agreement was evaluated by Kappa statistic for individual echocardiographic variables and overall cardiomyopathy grade. Agreement between raters overall impression and Cincinnati stage was also evaluated.

      Results

      Inter-rater agreement was low for individual echocardiographic variables as well as overall impression of RT cardiomyopathy severity (Table 1). A version of the Kappa statistic assessing agreement of the raters as a group indicated that the degree of agreement between qualitative cardiomyopathy grade and Cincinnati Stage was modest (0.35 0.10), although individual agreement was heterogenous (range, 0.05 - 0.44).
      Tabled 1
      Table thumbnail grt1

      Conclusion

      Inter-rater agreement for qualitative grading of cardiomyopathy findings is suboptimal using a simplified 4 chamber cardiac assessment. These data suggest that more precise, quantitative cardiac staging systems may be needed to reliably grade RT cardiomyopathy in TTTS. Further study may identify factors that reduce heterogeneity of qualitative assessment in TTTS cardiomyopathy.