(P-IG-24) Giving an Identity to an Unknown Antibody

Background/Case Studies: A 3-year-old, African American male was submitted for STAT antibody identification and crossmatch compatible red cell units, pre-renal biopsy. The patient previously underwent liver transplant due to fulminant hepatic failure with current diagnosis of hereditary hemolytic anemia and acute kidney injury. In addition, the patient received transfusion of red blood cells within the prior 3 months of sample submission.

Study

Design/Methods: The serological results from the initial patient testing displayed panreactivity with all cells tested, a negative direct antiglobulin test and negative autocontrol. It was suspected that the patient had developed an antibody against a high prevalence antigen. Human Erythrocyte Assay (HEA) BeadChip genotyping was requested to assist in determining if the patient was negative for any high prevalence antigens. To supplement the HEA testing, the patient’s red cells were tested against several in-house antisera for antigens not included in the HEA chip.



Monocyte monolayer assay (MMA) was performed to determine the clinical significance of the antibody. The MMA was initially performed using phenotype matched red cells for commonly encountered antigens. It was then performed once more using cells negative for the antigen the patient developed the antibody against.

Results/Findings: The HEA results did not reveal the patient to be negative for any of the high prevalence antigens on the chip. The initial MMA which was performed using cells negative for C, E, K, S, Fy^b, and Jk^b had an average monocyte index (MI) of over 80% (refer to Table 1); indicating that the antibody was clinically significant. Serological testing for Emm, En^a, Ch/Rg, At^a, Ge:2, Ge:3, Rh29, Lan, Rh17, and AnWj was performed and the patient was found to be negative for AnWj. A subsequent MMA was performed using red cells negative for AnWj as well as Lu(a-b-) cells with an MI of 0%. Crossmatch testing against AnWj negative and Lu(a-b-) red cells also provided compatible results.

Conclusions: The serological and MMA testing results verified that the patient had developed an alloanti-AnWj. In previous instances of alloanti-AnWj patients have been able to tolerate transfusion of AnWj positive cells. In this case due to the MI values being greater than 20% for all AnWj positive units, the patient would require AnWj negative or Lu(a-b-) cells for transfusion purposes.