Doppler ultrasonography for timing the third transfusion in fetal anemia from red cell alloimmunization

Abstract

ANEMIA FROM RED CELL ALLOIMMUNIZATION GIANCARLO MARI, ROLAND ZIMMERMANN, MARIA SEGATA, Wayne State University, Obstetrics & Gynecology, Detroit, Michigan, University Hospital of Zurich, Obstetrics and Gynecology, Zurich, Switzerland, UC, Ob/Gyn, Cincinnati, Ohio OBJECTIVE: The middle cerebral artery peak systolic velocity (MCA-PSV) has been successfully used for timing the first two transfusions in fetuses at risk for anemia because of maternal red cell alloimmunization. The objective of this study was to assess whether the correlation between the MCA-PSV and fetal hemoglobin is maintained in fetuses that had undergone two prior transfusions. STUDY DESIGN: Doppler measurement of MCA-PSV was performed before cordocentesis in 39 fetuses. The timing of the third transfusion was based on traditional criteria. The values of MCA-PSV and hemoglobin were expressed as multiples of the median (MoM). Anemia was defined as mild (hemoglobin !0.84 MoM for a given gestational age, moderate (hemoglobin !0.65 MoM), and severe (hemoglobin !0.55 MoM). Regression analysis was used to assess the correlation between the MCA-PSV and fetal hemoglobin. RESULTS: Gestational age at Doppler study ranged from 22 to 35 weeks. Six fetuses (15%) had normal hemoglobin concentration; 21 (53%) had mild anemia; 7 (20%) had moderate anemia; and 5 (12%) had severe anemia. There was a linear correlation between the MCA-PSV and fetal hemoglobin (R = .60) (P ! .05). CONCLUSION: Previously, concerns have been expressed about the accuracy of Doppler prediction of anemia after two prior transfusions. Our data suggests that there is a good correlation between the MCA-PSV and fetal hemoglobin in fetuses that have undergone two prior transfusions. Our findings expand the clinical situation in which Doppler can be used to monitor red cell alloimmunized pregnancies. 526 MIDDLE CEREBRAL ARTERY PEAK VELOCITY: ACCURACY AND RELIABILITY REBECCA PONDER, MICHAEL ESPLIN, ROBERT SILVER, YVETTE LACOURSIERE, JANICE BYRNE, University of Utah, Obstetrics and Gynecology, Salt Lake City, Utah, University of Utah, Department of OB/GYN, Salt Lake City, Utah OBJECTIVE: Peak systolic velocity of the fetal middle cerebral artery (MCA) has been used to identify fetal anemia in ‘‘at risk’’ pregnancies. Excellent accuracy has been reported in tertiary care centers with experienced sonographers and rigorous protocols. However, it is unclear if the test performs as well under less controlled circumstances. Our objectives were (1) to assess the accuracy of MCA peak velocity for the prediction of fetal anemia in patients at risk for red cell immunization, and (2) to assess the interand intra-observer variability of MCA peak velocity. STUDY DESIGN: (1) Retrospective cohort of women with red cell alloimmunization undergoing MCA doppler studies from 2000-2004. (2) Serial MCA Doppler studies were performed by 8 experienced sonographers without specific training in MCA doppler velocimetry in 4 uncomplicated pregnancies between 24-28 weeks gestation. Adequacy of studies was assessed by a blinded single investigator. RESULTS: 26 women at risk for red cell alloimmunization had 151doppler studies. 130/130 (100%) studies correctly predicted non-anemic fetuses. However, 10/21 (47%) studies indicating severe fetal anemia occurred in non-anemic fetuses (false positive rate: 47%). In the observer variability arm, 78 /108 (72%) studies were adequate. Interclass correlation coefficient (ICC) revealed no significant correlation between values obtained by practitioners on any individual subject, demonstrating poor reliability. CONCLUSION: Our false positive rate of 47% is substantially higher than previously reported and variability among practitioners was considerable. Published accuracy for MCA doppler may not be applicable to less experienced centers. While MCA doppler remains a good screening tool with a low false negative rate, the ‘‘positive’’ diagnosis of fetal anemia should be confirmed in non-hydropic cases. Specialized training, standardization, and quality assurance may improve accuracy of MCA Doppler for the detection of fetal anemia.