Platelet Function Testing to Monitor Clopidogrel Therapy in Cats
The mainstay of prevention of aortic thromboembolism and other thrombotic events is clopidogrel, however resistance to its effects has been well documented. Determination of clopidogrel effect is traditionally inaccessible to primary care veterinarians. This thesis investigates methods of analysis of samples for determination of clopidogrel effect.
Plateletworks ADP using the ProCyte Dx and ADVIA 2120 analyzer was run in healthy cats and cats receiving clopidogrel therapy, and results at different timepoints compared. Aggregation was significantly different between analyzers. Cohen’s kappa showed almost perfect agreement for determination of clopidogrel effect, and the AUCROC was 1.0. Lower limits of the aggregation reference interval in healthy cats were determined. CVs for platelet parameters were not different. There was no change in aggregation within one hour after phlebotomy.
Paired samples from healthy cats and cats receiving clopidogrel therapy were analyzed at point of care on the PFA-200 and after storage and shipping. While reference intervals differed for CT before and after shipping, the performance of the PFA-200 for determination of clopidogrel effect was comparable after shipping to before.
Client-owned cats were recruited prospectively, and blood donor cats retrospectively, to determine reference intervals for CT, PHC(1), and PHC(2). Cats on clopidogrel therapy were retrospectively included. No difference was found in the CT values for the healthy client-owned cats and blood donors. No difference in AUCROCs was found between tests.
The parameters PHC(1) and PHC(2) perform comparably to CT with both the COL/ADP and P2Y cartridges.
A retrospective review of closure curves was performed to determine those that exhibited Flow Obstruction and had paired analysis from the same blood sample that did not. Numerical analysis of the parameters Initial Flow and Total Volume, PHC(1) and PHC(2) was performed to evaluate if these could be used to determine if a sample exhibited clopidogrel effect. Curves were visually analyzed and characteristics identified that were more common in curves with or without clopidogrel effect. Visual analysis of curves was then performed. Numerical analysis of TV, PHC(1) and PHC(2) were able to differentiate clopidogrel effect. Visual curve analysis was unable to predict closure; agreement between reviewers was poor (K= 0.06).
Kornya MR, Abrams-Ogg ACG, Blois SL, Wood RD. Platelet function analyzer-200 closure curve analysis and assessment of flow-obstructed samples. Vet Clin Pathol. 2023 Jul 12. doi: 10.1111/vcp.13260. Epub ahead of print. PMID: 37438618.