A Practical Approach to Platelet Phenotype Profiling Using Microplate Aggregometry

Background/Objectives: Blood platelets exhibit substantial functional heterogeneity, yet no established principles exist for distinguishing their subpopulations. The present study proposes a methodology for the evaluation of platelet reactivity and inhibitor sensitivity, with the aim of facilitating the expeditious identification of platelet phenotypes under standard laboratory conditions. Methods: The phenotyping of healthy subjects was based on the study of platelet aggregation in response to agonists and inhibitors of P2Y₁₂, PAR-1 and GPVI receptors. The classification of variants was conducted on the basis of the similarities and differences in EC₅₀/IC₅₀ values obtained for individual ligands. Subsequently, the values were subjected to two- and six-variable cluster analyses. Results: Two major clusters (variants) were identified with consistent reliability across the range of analytical strategies employed. Cluster 1 comprised individuals with low EC₅₀ values and moderate to high IC₅₀ values, indicating high agonist responsiveness and relatively low inhibitor sensitivity. Conversely, cluster 2 exhibited the inverse pattern, characterised by moderate to high EC₅₀ values and moderate to low IC₅₀ values. Cluster 1 constituted a significant proportion of individuals (29-78%, depending on the analysis). The study did not identify a "low responder group". Conclusions: The proposed methodology is distinguished by two features: its flexibility and its accessibility. These characteristics enable the identification of any platelet phenotype associated with selected signalling pathway(s). The application of this approach has the potential to facilitate the identification of individuals at elevated cardiovascular risk, thereby informing personalised antiplatelet therapy in the context of primary prevention.