The same ehnancement methods (LISS, PEG) used to detect unexpected antibodies during pretransfusion testing can be used for prenatal antibody detection.Īn additional antibody screen may be ordered for Rh negative women at 26 to 28 weeks gestation to determine if active immunity to D has developed, before administration of RhIG prophylaxis. Antiglobulin testing should be done with anti-IgG reagent to detect clinically significant antibodies that are capable of crossing the placenta and causing hemolytic disease of the newborn (HDN). Giving Rh immune globulin to these women is not harmful.Īll women, regardless of their D type, should be tested during each pregancy for clinically significant antibodies, ideally at their first obstetrician visit. The clinical implication of this change is that a few women who actually have weak expression of the D antigen will be classified as Rh negative and will be candidates for Rh immune globulin. All women are now typed as either Rh negative or positive. The main reason is that today’s blood typing reagents are much more potent and most of the patients who were previously typed as weak D are now typed as Rh positive. The AABB has determined that weak D testing is no longer necessary for obstetric patients. Historically, if a patient typed as Rh negative, additional testing was then performed to determine if they had weak D expression. Serologic confirmation of the D type is also recommended at the beginning of each subsequent pregnancy. This recommendation is especially important as a safeguard to prevent an Rh negative woman from being falsely typed as Rh positive and denied RhIG. A record of the maternal ABO type is also helpful should the newborn infant develop signs and symptoms consistent with ABO HDN.ĭ typing should be done on at least two separate occasions and the results should be identical. Any discrepant results must be fully investigated. The results should not conflict with historical records. ABO typing is done primarily for patient identification. Repeat at 2-4 week intervals if below critical titerĪll women should be tested for ABO and D as early as possible in pregnancy, preferably during their first trimester visit. Rh or other clinically signficant antibody However, it is cost effective to perform a confirmatory tube test with PEG enhancement because 214 SPRCA assay samples were interpreted as having a negative antibody screen, thus allowing the release of valuable blood components for transfusion.3 rd trimester if history of antibodies or transfusion We report a high specificity for antibody screening using the SPRCA assay. The remaining 214 (68.4%) were negative, giving specificity for the SPRCA assay of 99.6 percent (48,985/ 49,199). Of these, 99 (31.6%) samples remained positive when tested with PEG enhancement. Of 49,084 samples, 313 (0.64%) were positive by the SPRCA assay. Testing was performed with strict adherence to the manufacturers' inserts. Further identification of positive samples was performed using a PEG enhancement method. Over a 5-month period, 49,084 donor serum or plasma samples were tested using the SPRCA assay. Positive results are then confirmed using a tube technique with polyethylene glycol (PEG) enhancement due to reported higher specificity than with SPRCA. Our blood bank routinely screens donors for antibodies using a solid-phase red cell adherence (SPRCA) assay.
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