A retrospective study of positive antibody screens at delivery in Rh-negative parturients

Abstract

Purpose Rhesus-(Rh-) negative women receiving anti-D antibodies antenatally often have a positive antibody screen at delivery. We investigated the incidence of positive antibody screens at delivery in this population and examined how the presence of positive antibody screens affected the time required to obtain type and screen or type and crossmatch results. Methods Records of parturients who had type and screen or type and crossmatch done upon presentation for delivery from June to October 2007 were examined to determine estimated gestational age at admission, Rh-status, the presence of positive antibody screens, and the time interval from receipt of specimen in the blood bank to the availability of antibody screen results. Results Of the 480 specimens sent for type and screen or type and crossmatch, 20% of parturients were Rh-negative, with 57% of those demonstrating a positive antibody screen compared with 4% of the Rh-positive parturients (P \ 0.01). In the Rh-negative group, 100% (95% CI 98-102) of positive antibody screens were anti-D antibodies. There was a longer median laboratory time for Rh-negative vs Rh-positive parturients (146 vs 65 min), for antibody positive vs antibody negative parturients (243 vs 65 min) (P \ 0.001 for both), but not for Rh-positive/antibody positive vs Rh-negative/antibody positive patients (312 vs 218 min) (P = 0.09). The antibody screen was positive in 100% of Rh-negative parturients until 37 weeks gestation, after which there was a decline. Conclusions Rh-negative parturients who receive anti-D antibodies antenatally have a higher incidence of positive antibody screens at delivery than Rh-positive parturients due to the presence of anti-D antibodies.

Guideline for blood grouping and red cell antibody testing in pregnancy

“…There is evidence that antibodies first detected after 28 weeks gestation are less likely to cause clinically significant HDFN (Rothenberg et al , ; Heddle et al , ). Further, and significantly, the introduction of RAADP has resulted in the detection of anti‐D Ig in samples taken after 28 weeks gestation from D‐negative women (Cambic et al, ). As it is not possible to differentiate between prophylactic anti‐D Ig and immune anti‐D until the latter has reached a high enough concentration in reference quantification to exclude the former, there is the potential for confusion between the two (New et al , ) (see Section 4.1).…”

Postpartum Hemorrhage on Labor and Delivery

“…40 †Extra time is needed to discriminate between anti-D antibodies due to RhoGAM and any additional antibodies that could interfere with a type and cross. 44 zThe exact number of units determined by a patient-specific assessment of risk for massive blood loss, and institutional resources to rapidly procure additional blood products. 43 CD ¼ cesarean delivery; FFP ¼ fresh-frozen plasma; Hct ¼ hematocrit; PPH ¼ postpartum hemorrhage; PRBC ¼ packed red blood cells; VB ¼ vaginal births.…”