Help With this Transfusion Medicine Problem. 1) A 30 year old group A positive m
ID: 3517182 • Letter: H
Question
Help With this Transfusion Medicine Problem.
1) A 30 year old group A positive man is being treated at your hospital for a relapse of acute leukemia. His leukemia was initially diagnosed 12 months ago, at which time he received 2 units of packed red blood cells. Three days ago he was readmitted to your hospital and required 2 units of blood. His antibody screening was negative three days ago and 12 months ago. His hematocrit which was 29% following the transfusion three days ago, is now only 24%. The patient has no obvious signs of bleeding and his physician orders 2 more units of blood to be transfused. After receiving the physicians order, you proceed to use the specimen collected three days ago as it doesn't expire until midnight tonight. Neither crossmatch shows hemolysis or agglutination at immediate spin, 370C phase or AHG phase.
During the transfusion of the first unit the patient develops a fever and chills and signs of a transfusion reaction, so the transfusion is stopped. A post-transfusion blood sample shows hemolysis, a positive direct antiglobulin test and the presence of anti-Jka. An eluate made from the recipients DAT positive red blood cells shows the presence of anti-Jka. The antibody screen and a DAT test is repeated on the pre-transfusion sample; these tests are negative.
a) What is a possible explanation for the drop in the patient's hematocrit from 29% to 24%?
b) If the patient had anti-Jka at the time of the acute hemolytic transfusion reaction, why were both crossmatches compatible?
Explanation / Answer
answer A. drop in hematocrit is due to hemolytic anemia.
answer B. The Jk antigen is important in transfusion medicine. People with two Jk(a) antigens, for instance, may form antibodies against donated blood containing two Jk(b) antigens (and thus no Jk(a) antigens). This can lead to hemolytic anemia, in which the body destroys the transfused blood, leading to low red blood cell counts.Kidd antibodies are dangerous as they are capable of causing severe acute hemolytic transfusion reactions ('kidd kills'). They are unique in that they are capable of dropping to low or even undetectable levels after several months following an exposure event.Thus, on pre-transfusion testing, an anti-Jka or -Jkb may go undetected. Following transfusion, a subsequent robust antibody response in the patient can occur (anamnestic response), resulting in hemolysis of the transfused red blood cells.
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