Diagnostic and prognostic significance of platelet large cell count and ratio in cats across stages of hypertrophic cardiomyopathy

Abstract

Hypertrophic cardiomyopathy (HCM) is the most common cardiac disease in cats and a major predisposing factor for arterial thromboembolism (ATE), a life-threatening complication. While platelet activation plays a pivotal role in thrombogenesis, the diagnostic and prognostic value of novel platelet-derived indices such as platelet-large cell count (PLCC) and platelet-large cell ratio (PLCR) remains poorly defined in feline patients. This study aimed to assess PLCC and PLCR across different stages of HCM and to evaluate their potential as biomarkers for thrombotic risk. Seventy-one client-owned cats were categorized based on the ACVIM guidelines into healthy controls (Stage A), asymptomatic HCM (Stage B), symptomatic HCM (Stage C/D), and HCM with ATE. PLCC was elevated (P < 0.01) in cats with HCM compared to controls, while PLCR showed a stepwise increase from Stage A to Stage C/D (P < 0.01). PLCC was reduced in cats with ATE (P < 0.05). A negative relationship was observed between platelet count and PLCR. However, a positive correlation was found between PLCC, platelet distribution width, and WBC count (P < 0.05). ROC curve analysis demonstrated optimal thresholds of PLCC >69 × 10⁹/L and PLCR ≤74 % for predicting ATE. Also, an Extreme Gradient Boost-based machine learning model was applied to predict FATE risk with SHAP (SHapley Additive exPlanations) analysis for model interpretation. The model demonstrated moderate discriminative ability (AUC-ROC = 0.68), with PLCC identified as the strongest predictor and PLCR as a contextual cofactor. These findings suggest that PLCC and PLCR may serve as informative adjunctive hematological parameters for assessing disease severity and stratifying thromboembolic risk in cats with HCM.