Correlations between biochemical and functional assays of platelet response to aspirin in healthy subjects and patients with ET. Individual percent inhibition values are depicted from healthy volunteers (n = 48) during aspirin treatment (100 mg daily) and following its withdrawal. The nonlinear relationships between percent inhibition of serum TXB₂ and Verify-Now Aspirin (A), AA-induced platelet aggregation (B), and urinary 11-dehydro-TXB₂ (C). (D) The relationship between absolute values of serum TXB₂ and Verify-Now Aspirin measurements performed in 15 ET patients during different aspirin regimens. The dotted line represents the best fitting of the experimental data (logarithmic relation between the 2 variables: y = 40ln[x] + 378, R² = 0.43; n = 75). Each point in the graph represents the median value for each aspirin regimen, and the horizontal and vertical bars indicate the correspondent interquartile range (25th to 75th percentile). bid, twice daily; EC, enteric coated aspirin; od, once daily. Reprinted from Santilli et al⁶⁰  and Pascale et al²⁵  with permission.