Reassessment of Critical Anti-D Antibody Titer in RhD Alloimmunized Antenatal Women
Bharat Singh, Rajendra Chaudhary, Rahul Katharia
Abstract
OBJECTIVE: In the setting of RhD-alloimmunized pregnancy, laboratory variations in critical titer (CT) of anti-D antibody may result in needless referrals or a compromised fetal outcome. METHODS: RhD-alloimmunized pregnant women were included. Fetal outcome was categorized based on cord hemoglobin and interventions required. For 3 commonly used CTs of 8, 16, and 32, sensitivity and specificity as well as positive and negative predictive values were computed. RESULTS: When compared with CTs of 16 and 32, we detected 6.9% and 19.4% more cases of moderate-severe hemolytic disease of the fetus and newborn by using 8 as the CT. However, this leads to greater rate of unnecessary referral (12.1%, 10/82) than a CT of 16 (8.2%, 6/73) and 32 (4.9%, 3/61). A CT of 8 demonstrated 100% sensitivity, but 12.1% (10/82) of patients were referred needlessly. CONCLUSION: Because of its 100% sensitivity, we advocate decreasing the CT to 8. However, this may lead to unwarranted referrals.