Recognition of the feline red blood cell (RBC) antigen Mik and the presence of naturally occurring anti-Mik antibodies resulting in acute hemolytic transfusion reactions prompted the recommendation to perform a blood crossmatch prior to a cat’s first RBC transfusion. The objectives of this retrospective study were: 1) to determine the prevalence of naturally occurring non-AB RBC alloantibodies detectable by tube crossmatch, and 2) to compare transfusion outcomes in feline patients with and without a tube crossmatch performed. In addition, a limited prospective study was undertaken to compare results of the gel and tube methods for feline crossmatch.
Medical records of 300 cats that received a RBC transfusion and/or major crossmatch between January 1, 2013 to December 31, 2016 were reviewed retrospectively. Information recorded included previous transfusion history, major and minor crossmatch results (tube method), volume of pRBCs administered, pre- and post-transfusion PCV, adverse events, and patient outcome. For 10 cats, a crossmatch was performed using both the gel and tube methods for comparison.
RBC compatibility data was available for 154 transfusion naïve cats, 23 (14.9%) of which showed some degree of incompatibility (1+ to 3+ hemagglutination) on the major crossmatch to 1 or more donors. Of 55 cats previously transfused, 15 cats (27%) were incompatible (1+ to 2+ hemagglutination) on the major crossmatch to 1 or more donors, significantly more than in the transfusion naïve group (P = 0.042). Packed RBC transfusions were administered to 249 cats, and a tube crossmatch was performed for 167 cats (67%) prior to their first pRBC transfusion; the remaining 82 cats received type-compatible, non-crossmatched pRBCs. The median volume of pRBCs administered during the first transfusion was 5.3 mL/kg (range, 2.4-18). The median increase in PCV post-transfusion was 5%; cats receiving crossmatch-compatible pRBCs did not have a greater increase compared to those without a crossmatch. Febrile transfusion reactions occurred more often in cats that received typed, non-crossmatched pRBCs (n = 8) than cats administered crossmatch-compatible pRBCs (n = 4) (P = 0.022). Of the 246 cats receiving pRBC transfusions, 188 (76.4%) survived to hospital discharge. A pre-transfusion crossmatch was not associated with improved survival to discharge or at 30 or 60 days post-transfusion.
A crossmatch was performed using both the tube and gel method for 10 cats (total of 31 crossmatches). For 9 recipient cats (24 crossmatches), there was agreement between results of the tube and gel methods, with the exception of 1 cat having a 2+ and 3+ major incompatibility to the same donor with the tube and gel methods, respectively, likely a result of the subjectivity of grading. Differing results observed for 1 cat, with a negative tube but 4+ mixed field agglutination gel result for autocontrol and major crossmatch tests with 3 donors, were attributed to marked rouleaux. Microscopic evaluation and saline replacement during the tube crossmatch supported an interpretation of rouleaux rather than hemagglutination.
RBC incompatibility noted in 15% of transfusion naïve cats suggests that the prevalence of naturally occurring non-AB RBC alloantibodies is sufficiently high to justify the recommendation to perform a blood crossmatch prior to all (including the first) RBC transfusions in cats.
Small Animal Internal Medicine Resident
University of Pennsylvania
Megan McClosky received her veterinary degree from Auburn University in 2014, and completed her rotating internship at the University of Pennsylvania. She is currently in her third year of an internal medicine residency at the University of Pennsylvania.
Friday, June 15
8:00 AM – 8:15 AM
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