FINAL DIAGNOSIS: ACUTE HEMOLYTIC TRANSFUSION WITH JKA ANTIBODY
When investigating a hemolytic transfusion reaction at least three investigations are performed (1). First, there is a check for clerical error, which is the most common cause of transfusion reactions. The plasma and preferably urine are checked visually for evidence of hemolysis. A direct antiglobulin test (DAT) is performed to determine the presence of antibodies on the surface of cells. If positive, an eluate of the antibodies is taken to find the specificity of the type.
A screen and panel may also be performed to determine the presence of antibody in the patient's serum. Finally, the patient's RBC phenotype may be performed to rule out autoantibodies.
A variety of techniques can be used to enhance detection of antibodies (2). The most common involve modifying the reaction medium. This includes using low ionic strength solutions (LISS), polyethylene glycol (PEG), or albumin in the IAT or DAT reaction medium. Albumin enhances aggregation by bringing antibody-coated cells closer together. The LISS reaction enhances antibody uptake and allows the reaction time to decrease. PEG removes water, thereby effectively concentrating the antibody. In this case, the PEG eluate and screen successfully revealed the presence of Jka antibody (3).
The Kidd system was first discovered in 1951 when an anti-Jka was found in the serum of a Mrs. Kidd. The protein structure was subsequently determined to be a 45KD transmembrane protein . It is unaffected by enzymatic modification by chloroquine,AET,DTT or acid. There are 2 alleles Jka and JKb, which are codominant. They have been localized to chromosome 18q11-12. Roughly, 50% of whites and Asians are Jk(a+,b+), while 57% of blacks are Jkb- .
Kidd antibodies are of the IgG class. They bind well to compliment and are therefore capable of causing intravascular as well as extravascular hemolysis - as in this patient (4). Kidd antibodies are found in very low titers and are difficult to detect. There can, however, be a strong amnestic response from previous exposure, resulting in delayed or even acute hemolytic reactions. Detection can be enhanced with PEG or LISS or by using enzymes such as papain or ficin.
This patient was treated with intravenous fluids, oxygen and alkalinization of urine. She improved was subsequently discharged.
Contributed by Raj Hari, MD