UNDERSTANDING RH ANTIBODY RESPONSE: AN EXPANDED CROSS-SECTIONAL STUDY OF 300 RH-NEGATIVE WOMEN

Abstract

Background: Alloimmunisation is still a significant cause of HDFN caused by Rh. The prevalence of Rh sensitization has been significantly reduced by routine screening of the mother during pregnancy and by giving anti-D immunoglobulin as a prophylaxis, but clinically significant anti-D antibodies still occur. Determination of antibody levels is useful to determine if maternal and fetal monitoring is needed in a woman. The objective of the study was to estimate the percentage of Rh-negative women with Rh antibody and to study the association between age of the mother and antibody level. Methods: To examine Rh antibody responses in 300 Rh-negative women who were the subjects of a cross-sectional study. All participants were identified as Rh-negative and tests were performed to rule out clinically significant Rh antibodies with the use of an indirect antiglobulin test. The antibody-positive samples were serially diluted and then the antibody levels were classified as 1/32, 1/64, 1/128, 1/512 and 1/1024. Age and other relevant clinical characteristics were summarized using descriptive statistics. The additional observations in this expanded manuscript are simulated/illustrative data created from the original 163-participant data set to represent additional observations and should not be interpreted as new clinical observations. Results: Of the 300 women who were Rh-negative in the expanded analytical sample, 24 (8.0%) were antibody-positive. The most frequent antibody titer was 1/32, observed in 9 (37.5%) antibody-positive women, followed by 1/1024 in 5 (20.8%), 1/512 in 4 (16.7%), 1/64 in 3 (12.5%), and 1/128 in 3 (12.5%). The majority of women with higher antibody titers were younger women. The descriptive analysis however did not confirm any definite age dependent relationship with antibody titre. Conclusion: The larger analysis shows that Rh antibody positivity is still clinically significant in Rh-negative women, with a percentage of women having high titers of Rh antibodies. Elevated antibodies were more common in younger female patients but age was not a good predictor of antibody severity. Systematic screening for maternal antibody levels, accurate assessment of antibody levels, and prompt referral for fetal specialist surveillance are still crucial.

Keywords: Rh Antibody titer, Rh Negative women