Inaccurate Doses of Rh Immune Globulin After Rh-Incompatible Fetomaternal Hemorrhage: Survey of Laboratory Practice (Cap Laboratory Improvement Programs) (Report)

Inaccurate Doses of Rh Immune Globulin After Rh-Incompatible Fetomaternal Hemorrhage: Survey of Laboratory Practice (Cap Laboratory Improvement Programs) (Report)

Rh immune globulin (RhIG) provides prophylaxis against alloimmunization to the D blood group antigen in Rh(D)-negative patients who are exposed to Rh(D)-positive red blood cells (RBCs) by pregnancy or transfusion. Rh(D)-negative women are given RhIG in the early third trimester and again after delivery of an Rh(D)-positive infant, and also during pregnancy for events that may have associated fetomaternal hemorrhage (FMH), such as abdominal trauma, vaginal bleeding, ectopic pregnancy, fetal death, and invasive obstetric procedures. (1) The presence of passive anti-D suppresses the patient’s own immune response. The mechanism of action is still uncertain, but the removal of Rh(D)-positive RBCs from the circulation by the antibody is an important component. (2) A total of 20 [micro]g RhIG is sufficient to protect against 1 mL Rh(D)-positive RBCs. In North America, the most common obstetric RhIG dose formulation contains 1500 IU (often expressed as 300 [micro]g), enough to abrogate the alloimmunization risk from 15 mL RBCs (or about 30 mL of fetal whole blood). However, FMH greater than this volume occurs in 3 in 1000 deliveries, requiring more than 1 dose of RhIG for adequate prophylaxis. (3) Guidelines have varied on whether to test for excess FMH after all Rh(D)-incompatible deliveries or only for those with clinical risk events. However, many episodes of excess FMH are not associated with a clinical risk event. (4) Obstetric guidelines in the United States and United Kingdom (5,6) call for routine testing, in agreement with the specific laboratory accreditation requirement of the College of American Pathologists (CAP) for routine FMH testing (checklist item TRM.40790), (7) and the general requirement of the AABB (formerly the American Association of Blood Banks) for ensuring that an adequate RhIG dose is given after all Rh(D)-incompatible deliveries (standard 5.20.3). (8)

Inaccurate Doses of Rh Immune Globulin After Rh-Incompatible Fetomaternal Hemorrhage: Survey of Laboratory Practice (Cap Laboratory Improvement Programs) (Report)

Inaccurate Doses of Rh Immune Globulin After Rh-Incompatible Fetomaternal Hemorrhage: Survey of Laboratory Practice (Cap Laboratory Improvement Programs) (Report) | | 4.5