Diagnostic evaluation of a flow cytometry-based direct antiglobulin test and demographic analysis in dogs with suspected immune thrombocytopenia.

Flow cytometry DAT with a 10% IgG-bound platelet cutoff, combined with demographics, improves canine ITP diagnosis.

This study evaluated a flow cytometry-based direct antiglobulin test (DAT) for diagnosing canine immune thrombocytopenia (ITP), a condition where antibody-mediated platelet destruction leads to thrombocytopenia. Researchers enrolled 100 healthy control dogs and 1,127 thrombocytopenic dogs, staining platelets with anti-CD41/61 and anti-canine IgG antibodies for flow cytometric analysis. A diagnostic cutoff of 10% IgG-bound platelets was established from healthy controls, resulting in 39.3% of thrombocytopenic dogs being classified as DAT-positive. DAT-positive dogs demonstrated significantly lower platelet counts compared to DAT-negative dogs (median 10,000/µL vs. 39,000/µL; P < 0.05), and a weak but statistically significant inverse correlation existed between IgG-bound platelet percentage and platelet count (r = -0.17, P = 0.0062). Demographic analysis identified mixed-breed and Shih Tzu dogs, young to middle-aged individuals, and intact females as having increased odds of DAT positivity, consistent with known patterns of autoimmune disease predisposition. These findings support integrating flow cytometry-based DAT results with platelet counts and patient demographics to enhance the diagnostic workup for canine ITP. The test offers a more objective, in-house diagnostic tool compared to subjective or indirect methods. However, the weak correlation between IgG binding and platelet count suggests DAT positivity alone is insufficient for definitive diagnosis, and clinical interpretation should incorporate multiple diagnostic parameters to guide therapeutic decision-making in suspected ITP cases.

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