| As discussed earlier, one of the post-analytic tools for confirming that the serologic data fit the solution is to consider the big picture, as presented below. Think of how you would reply to each question in this case and then click each question to see sample responses. | View Page |
| The p value in this case This CaseWith the panel done 2 weeks post-transfusion, 5 panel cells that were Jk(a+) reacted and 5 that were Jk(a-) did not. This yields a p value of 0.004, which is less than the standard of 0.05, and therefore is more than acceptable statistically. In other words, an antibody other than anti-Jka would be expected to produce these panel results only 4 times in 1000 (which is pretty unlikely).Th true p value is much lower because many more cells were tested than in the panel alone.Concluding that the antibody is anti-Jka is further strengthened because the patient's red cells type as Jk(a-).Learning points: The most important things to know about statistical tools such as p values are that they Relate to the probability of getting the observed results if the null hypothesis were true (the panel results were due to another antibody) Do not substitute for technical and clinical judgment. | View Page |
| Summary This case study presents a scenario in which a patient had an unexpected antibody that disappeared after he was transfused with 2 units of unmatched group O Rh negative RBC. The patient developed a positive DAT with MFA but an antibody identification using the post-transfusion red cell eluate was inconclusive, making the antibody unidentifiable. Fortunately, the patient improved and further transfusion was not required. Ultimately, the patient's antibody was identified as anti-Jka, with a second antibody to a low frequency antigen (Radin) also unexpectedly present.The case illustrates the risks involved in using unmatched blood. | View Page |
| Pretransfusion Direct Antiglobulin Test Result The laboratory obtained post-transfusion blood specimens in order to perform a serological investigation. Pretransfusion and post-transfusion DATs were performed. Patient cells DAT CC Pretransfusion 0 2+ DAT = direct antiglobulin test with polyspecific antiglobulin serumCC = IgG sensitized RBC | View Page |
| Post-transfusion DAT Results Patient cells DAT CC Post-transfusion 2+ mixed field agglutination (MFA) N/A | View Page |
| Which of the following statements about mixed-field agglutination (MFA) are true? Select all that are correct. | View Page |
| Antibody investigation Immediate post-transfusion antibody identification results Cell Rh Rhesus Kell Duffy Kidd MNSs P Lewis Lu Results1 Results2 C D E c e Cw K k Kpa Fya Fyb Jka Jkb M N S s P1 Lea Leb Lua Gel IAT Gel IAT 1 rr 0 0 0 + + 0 0 + 0 + 0 + 0 0 + + + +S + 0 0 0 w+ 2 rr 0 0 0 + + 0 0 + 0 0 + + + 0 + + + +S + 0 0 0 0 3 rr 0 0 0 + + 0 0 + 0 + 0 0 + 0 + + 0 + 0 + 0 0 0 4 r"r 0 0 + + + 0 0 + 0 + + 0 + 0 + 0 + + + 0 0 0 0 5 R2R2 0 + + + 0 0 + 0 0 + 0 + + + 0 + 0 + 0 | View Page |
| Which of the following most likely accounts for the patient's post-transfusion plasma giving negative panel results? | View Page |
| Other post-transfusion tests The patient's post-transfusion plasma was also retested with the 6 RBC that tested positive initially. Like the antibody panel done on the post-transfusion plasma, they are now all negative by gel IAT.Unfortunately, the panel results with the patient's post-transfusion eluate do not give clear results (only cells #1 and #9 react) and the antibody remains unidentifiable. Suppose that the physician had decided to continue transfusing the patient at this stage. Take a moment to think about what you would advise regarding the compatibility of such transfusions, all of which appear to be compatible in the crossmatch. When you have considered the options, continue to the next page. | 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 |
| Investigating weak antibodies In this case the patient's antibody has disappeared from the plasma by adsorbing to transfused donor red cells. It is detectable but unidentifiable in the post-transfusion red cell eluate. Several trial and error procedures exist to enhance weak antibodies. Which methods will enhance the reactivity of a given antibody depend on its characteristics. Methods to investigate weak antibodies include: Use a higher plasma to red cell ratio (add more antibody-containing plasma or eluate) Increase incubation time (if consistent with manufacturer instructions, if applicable) Use enzyme-treated panel red cells (enzymes enhance IgG antibodies in Rh and Kidd blood systems but denature some antigens, e.g., Fya, Fyb, S) Try alternative antibody detection methods, e.g., if using LISS routinely, try polyethylene glycol (PEG) or column agglutination methods such as gel, providing they have been validated for use in the TS laboratory. | View Page |
| Antibody identification (2 weeks post-transfusion) Fortunately, the patient's condition stabilized and additional transfusions were not required. Two weeks later, new patient specimens were drawn for antibody studies. Antibody identification results Cell Rh Rhesus Kell Duffy Kidd MNSs P Lewis Lu Results Cell C D E c e Cw K k Kpa Fya Fyb Jka Jkb M N S s P1 Lea Leb Lua Gel IAT* 1 rr 0 0 0 + + 0 0 + 0 + 0 + 0 0 + + + +S + 0 0 1+ 1 2 rr 0 0 0 + + 0 0 + 0 + 0 + + 0 + + + +S + 0 0 w+ 2 3 rr 0 0 0 + + 0 0 + 0 + + 0 + 0 + + 0 + 0 + 0 0 3 4 r"r 0 0 + + + 0 0 + 0 + + 0 + 0 + 0 + + + 0 0 0 4 5 R2R2 0 + + + 0 0 + 0 0 + + + + + 0 + 0 + 0 | | 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 |
| DAT change of status Notice that the patient's DAT is now negative (IAT autocontrol in the panel done 2-weeks post-transfusion is negative). Cell Rh Rhesus Kell Duffy Kidd MNSs P Lewis Lu Results Cell C D E c e Cw K k Kpa Fya Fyb Jka Jkb M N S s P1 Lea Leb Lua Gel IAT* 1 rr 0 0 0 + + 0 0 + 0 + 0 + 0 0 + + + +S + 0 0 1+ 1 2 rr 0 0 0 + + 0 0 + 0 + 0 + + 0 + + + +S + 0 0 w+ 2 3 rr 0 0 0 + + 0 0 + 0 + + 0 + 0 + + 0 + 0 + 0 0 3 4 r"r 0 0 + + + 0 0 + 0 + + 0 + 0 + 0 + + + 0 0 0 4 5 R2R2 0 + + + 0 0 + 0 0 + + + + + 0 + 0 + 0 + 0 w+ 5 6 | View Page |
| Antigen phenotyping A standard follow-up to antibody identification is to antigen phenotype: Patient's red cells (expecting them to lack the corresponding antigen) Donor red cells (in this case, those transfused before an antibody was identified, or, more typically, to find suitable antigen-negative donors to crossmatch prior to transfusion).If you had wanted to type the patient for any antigens at this point in the investigation (2-weeks post-transfusion), which specimen would you have used? Think about any antigen typing problems and how to overcome them before proceeding to the next page. | View Page |