Rh-negative Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Rh-negative and links to relevant pages within the course.
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| Which of the following set of conditions would preclude HDN as a result of Rh incompatibility: | View Page |
| Case Presentation Mr. R.M., a 55-year old male, was admitted to a hospital emergency department with severe lower gastrointestinal bleeding. His history revealed multiple prior transfusions, the last of which he received five years earlier.Physical examination revealed hemodynamic instability (systolic BP 60 mmHg). Blood tests revealed a hemoglobin (Hb) of 8 g/dL (80 g/L) and a hematocrit (HCT) of 28% (0.28). The patient received aggressive fluid resuscitation with Ringer's lactate and was sent to the operating room (OR) for an emergency laparotomy.The physician ordered four units of Red Blood Cells to be crossmatched.Two units of uncrossmatched group O Rh-negative Red Blood Cells were also ordered and authorized for immediate emergency transfusion. | View Page |
| Transfusion Service Laboratory The transfusion service laboratory (TS) instructed clinical staff to draw blood specimens for compatibility testing before transfusing any blood components or products.Once the blood samples were collected, the clinical staff immediately began transfusing the patient with the O Rh-negative blood. | View Page |
| ABO, Rh and antibody screen These ABO, Rh, and antibody screen results were obtained by the TS using the blood specimen that was collected prior to starting the emergency transfusion with O Rh-negative RBCs. ABO and Rh typing ABO Forward Group ABO Reverse Group Rh anti-A anti-B A1 cells B cells anti-D 0 0 4+ 4+ 3+ Antibody screen Cells Gel IAT* Screen Cell I 3+ Screen Cell II 2+ Screen Cell III 2+ * IAT = indirect antiglobulin test | View Page |
| The antibody screen is positive but the transfusion of the O Rh-negative RBCs is already in progress. What are the transfusion service (TS) laboratory's priorities in this case?Place the following procedures that will be followed by the TS in the appropriate order of priority. | View Page |
| Crossmatch Results These are the results of the crossmatch that was being performed in the transfusion service laboratory while the patient was receiving the two units of O Rh-negative RBCs. Cells Gel IAT* Donor I** 2+ Donor 2** 2+ Donor 3 3+ Donor 4 3+ Donor 5 2+ Donor 6 3+ * IAT = indirect antiglobulin test ** O Rh-negative RBC (Donors 3 - 6 are O Rh-positive) | View Page |
| Consulting the patient's physician If the physician had decided to continue transfusing the patient at this stage, the following information should be communicated: Although all donors appear to be compatible in the post-transfusion crossmatch, they are not. The results are false negatives - the patient's antibody has been "mopped up" by adsorbing to the incompatible transfused O Rh-negative RBC. Given that 6 donors were positive using the pretransfusion plasma, the antigen is a higher frequency antigen and most donors would likely be antigen-positive and incompatible. The patient's physician should consult the TS medical director before any decision to transfuse is made. Transfusing RBC before tests are complete requires physicians to sign an emergency release form in which they assume full responsibility. | View Page |
| Variations in antibody strength The antibody in the pretransfusion specimen (prior to the patient being transfused with two units of unmatched group O Rh-negative RBC) reacted 2+ and 3+ with antibody screen and donor cells.If Jk(a+), the transfused donor RBC would have stimulated increased antibody production and the patient's plasma would be expected to react even more strongly with Jk(a+) red cells than in the pretransfusion specimen.However, the expected increase in antibody strength did not happen. Because Jk(a+) donor cells "mop up" (adsorb) the patient's anti-Jka, initially the anti-Jka decreased in strength. Later, once donor red blood cells are no longer present to adsorb the antibody, the anti-Jka would be expected to become stronger.Currently, (2-weeks post-transfusion) the patient's plasma is only reacting 1+ with Jk(a+b-) RBC and w+ with Jk(a+b+) RBC.This effect is called dosage. Learning points When a secondary immune response occurs, antibody first decreases before it increases. The expected increase in antibody strength will vary depending on the amount of excess antibody available in the patient's plasma at the time of testing versus the amount that had adsorbed to donor rbc and been removed by EVH.~ | View Page |
| When the patient's plasma was non-reactive with panel cells, and very weak and unidentifiable in the post-transfusion RBC eluate, no attempt was made to try to enhance the weak antibodies.We now know that the patient has anti-Jka and that it disappeared rapidly from the patient's plasma after transfusion with two group O Rh-negative RBC. Consider the question below, then click on the question to receive the answer. | View Page |
| Antigen phenotyping results The patient's pretransfusion red cells and all donor red cells involved in the case (two group O Rh-negative RBC and four group O Rh-positive red cells initially crossmatched) were phenotyped for Jka.As expected, the patient typed as Jk(a-). The six donor RBC that were incompatible in the initial crossmatch were Jk(a+).The frequency of the Jka gene in Caucasians is ~77%, with most Caucasian red cells (50%) typing as Jk(a+b+). | View Page |