title: Correlation between light transmission aggregometry, VerifyNow P2Y12, and VASP-P platelet reactivity assays following percutaneous coronary intervention.
abstract: BACKGROUND
  High on-treatment platelet reactivity is an established risk factor for adverse cardiac events in patients taking clopidogrel following percutaneous coronary intervention (PCI).
  
  
  METHODS
  Two hundred patients underwent platelet reactivity testing with VerifyNow P2Y12, vasodilator-stimulated phosphoprotein phosphorylation (VASP), and light transmission aggregometry (LTA) with both 5 and 20 μM of adenosine diphosphate (ADP) following PCI. High on-treatment platelet reactivity was defined as a maximum platelet aggregation ≥46% for LTA ADP 5 μM or ≥60% for 20 μM; platelet reactivity index (PRI) ≥50% for VASP; and platelet reactivity units ≥235 for VerifyNow. Correlation between assays was tested using Spearman coefficients (ρ); agreement among tests in regards to high on-treatment platelet reactivity was evaluated with Kappa statistics (κ).
  
  
  RESULTS
  All Spearman correlations had P values <0.001, although ρ ranged from 0.60-0.86. The incidence of high on-treatment platelet reactivity was 39.3% with VASP, 27.3% with VerifyNow, 23.1% with LTA ADP 5 μM, and 16.2% with LTA ADP 20 μM. The strongest correlation was between LTA ADP 5 μM and LTA ADP 20 μM (κ= 0.53, 95% CI 0.37-0.68); the weakest was between VASP and LTA ADP 5 μM (κ= 0.33, 95% CI 0.19-0.47). Overall, the level of agreement between assays was in the moderate to poor range.
  
  
  CONCLUSIONS
  Despite evidence that the most commonly used tests are correlated, agreement among tests is modest at best and demonstrates they are not interchangeable.
authors.affiliation: Washington Hospital Center, Washington, DC 20010, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gaglia
authors.forename: Rebecca
authors.initials: R
authors.lastname: Torguson
authors.forename: Rajbabu
authors.initials: R
authors.lastname: Pakala
authors.forename: Zhenyi
authors.initials: Z
authors.lastname: Xue
authors.forename: Gabriel
authors.initials: G
authors.lastname: Sardi
authors.forename: William O
authors.initials: WO
authors.lastname: Suddath
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Kent
authors.forename: Lowell F
authors.initials: LF
authors.lastname: Satler
authors.forename: Augusto D
authors.initials: AD
authors.lastname: Pichard
authors.forename: Ron
authors.initials: R
authors.lastname: Waksman
mesh_terms: D015906:Angioplasty, Balloon, Coronary / Q000295:instrumentation* / Q000379:methods; D015815:Cell Adhesion Molecules; D016001:Confidence Intervals; D054855:Drug-Eluting Stents; D005260:Female; D006801:Humans; D008297:Male; D008840:Microfilament Proteins; D008875:Middle Aged; D010750:Phosphoproteins; D010974:Platelet Aggregation / Q000187:drug effects*; D010979:Platelet Function Tests / Q000295:instrumentation / Q000379:methods; D058925:Receptors, Purinergic P2Y12 / Q000187:drug effects; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013997:Time Factors; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D058925:Receptors, Purinergic P2Y12; D000098662:Vasodilator-Stimulated Phosphoprotein