A case series highlighting a common approach to identifying anti-Jk3

The Kidd-null phenotype, Jk(a–b–), is rare, and a patient with this phenotype may develop anti-Jk3, a red blood cell (RBC) antibody reactive with a domain common to both Jk^a and Jk^b. Like other antibodies to high-prevalence antigens, the presence of this antibody poses challenges in the immunohematologic evaluation of these patients. Thoughtful laboratory testing is necessary to resolve the antibody specificity and to reveal other underlying antibodies. Moreover, the rarity of the Kidd-null phenotype makes finding blood donors difficult for those who need transfusion and have developed anti-Jk3. This review describes methods used in identifying anti-Jk3 in four pregnant patients. Blood bank records were retrospectively reviewed to illustrate the common approach in anti-Jk3 identification. In all cases, pertinent blood bank history was gathered, and extended RBC phenotyping was performed, followed by adsorption studies and testing of selected RBCs. Underlying antibodies were found in two of the cases. This review also reiterates some common challenges encountered with Kidd antibody analysis and highlights the importance of patient ethnic ancestry and obtaining accurate patient transfusion history.