The feline AB blood group system (blood types A, B, and AB) encoding the cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH) gene is the most significant in transfusion medicine and hemolysis of the newborn for cats. Blood typing and cross-matching in pre-transfusion testing are crucial to determining blood compatibility and thus prevent hemolytic transfusion reactions. We here performed serological and genetic investigations to characterize blood samples from cats with discordant results for card agglutination (CARD) and the alloantibody agglutination test for blood typing in two cats (subjects K and R). Subject K showed incompatible cross-matching in pre-transfusion testing. Red blood cells from subjects K and R determined blood type B from the CARD method showed blood type AB by alloanti-A and alloanti-B antibodies in agglutination testing. Genomic DNA sequencing of the coding region (exons 1a to 14) for the cat CMAH gene showed that subject K had four mutations with heterozygosity at c.139C>T, c.179G>T, c.327A>C, and c.364C>T. Similarly, the CMAH gene of subject R carried six mutations with heterozygosity at c.142G>A, c.187A>G, c.268T>A, c.327A>C, c.773G>A and c.1603G>A, representing a new diplotype including a novel synonymous single nucleotide polymorphism (SNP) in exon 7 (c.773 G>A: Arg258Gln). The CMAH diplotype in subjects K and R was different from major diplotype in blood type B cats. This study is the first to report CMAH variants in cats with discordant blood types between CARD and TUBE methods. These results could assist in the classification of feline AB blood types for transfusion medicine to avoid blood incompatibilities.

猫 AB 血型系统（血型 A、B 和 AB）编码胞苷单磷酸-N-乙酰神经氨酸羟化酶（CMAH)基因在猫的输血医学和新生儿溶血中最为重要。输血前测试中的血型和交叉配型对于确定血液相容性至关重要，从而防止溶血性输血反应。我们在这里进行了血清学和遗传学调查，以表征来自猫的血液样本，其卡片凝集 (CARD) 和同种抗体凝集试验对两只猫（受试者 K 和 R）的血型分析结果不一致。受试者 K 在输血前测试中表现出不相容的交叉匹配。来自受试者 K 和 R 的红细胞通过 CARD 方法确定 B 型血，在凝集试验中通过同种异体抗 A 和同种异体抗 B 抗体显示血型为 AB。猫编码区（外显子 1a 至 14）的基因组 DNA 测序CMAH基因显示受试者K有四个杂合性突变，c.139C>T、c.179G>T、c.327A>C和c.364C>T。同样，该CMAH受试者R基因携带6个杂合性突变，c.142G>A、c.187A>G、c.268T>A、c.327A>C、c.773G>A和c.1603G>A，代表一个新的双倍型包括外显子 7 中新的同义单核苷酸多态性 (SNP)（c.773 G>A：Arg258Gln）。这CMAH受试者 K 和 R 的双倍型与 B 型血猫的主要双倍型不同。这项研究是第一个报告CMAHCARD 和 TUBE 方法之间血型不一致的猫的变异。这些结果有助于对用于输血药物的猫科动物 AB 血型进行分类，以避免血液不相容性。