Intraobserver and interobserver variability of transabdominal Doppler velocimetry measurements of the fetal ductus venosus between 10 and 14 weeks ofgestation

Objective To assess the intraobserver repeatability and interobserver repro ducibility of transabdominal Doppler ultrasound measurements of ductus veno sus blood flow in fetuses between 10 and 14 weeks of gestation. Design A prospective study with the following end-points: coefficient of va riation, intraclass correlation coefficients within and between observers, repeatability coefficient and Cohen's kappa coefficient. Subjects and Methods Doppler velocimetry indices (maximum peak systolic vel ocity during ventricular systole, end-diastolic velocity during atrial cont raction, peak systolic velocitylend-diastolic velocity ratio and pulsatilit y index for veins) were successfully measured three times by the same train ed observer in 67 fetuses. Of these, in 24 fetuses, the measurements were t hen repeated by a second trained observer. In addition, both observers clas sified qualitatively the blood flow as being normal or abnormal with regard to the presence or absence/reversal of flow during atrial contraction. Results The intraobserver repeatability of the pulsatility index for veins measurements was considered good with a coefficient of variation of 8.9% an d an intraclass correlation coefficient value of 0.62. However, inconsisten cies occurred in maximum peak systolic velocity, end-diastolic velocity and systolic/diastolic ratio measurements, which had coefficients of variation of 19%, 28.5%, and 25.4%, respectively. The corresponding intraclass corre lation coefficient values were 0.70. 0.69 and 0.60. Interobserver reproduci bility of these indices was unsatisfactory, the coefficient of variation va rying between 11.5% and 47.2% and the intraclass correlation coefficient be tween 0.18 and 0.44. Agreement between the repeated observations with regar d to interpretation of normal or abnormal blood flow varied from moderate ( interobserver) to very good (intraobserver). Conclusions There was considerable variability in all Doppler indices excep t for the intraobserver repeatability of the pulsatility index for veins me asurement. This makes the implementation of the semiquantitative Doppler in dices in a screening setting difficult. On the contrary, qualitative classi fication of the flow velocity waveforms seemed to be a reproducible method.