title: Platelet aggregation is dependent on platelet count in patients with coronary artery disease.
abstract: BACKGROUND
  Platelet function testing in whole blood is widely used to evaluate the effect of antiplatelet agents, but it is not known whether results are affected by whole blood parameters. This study investigated the importance of platelet count, haematocrit, red blood cells (RBC), and white blood cells in whole blood platelet aggregometry.
  
  
  METHODS
  We included 417 patients with coronary artery disease on aspirin mono-therapy and 21 aspirin-naïve healthy individuals. Blood sampling was performed one hour after aspirin ingestion. The antiplatelet effect of aspirin was evaluated using the VerifyNow® Aspirin assay and multiple electrode aggregometry (MEA, Multiplate®) induced by collagen (1.0 μg/mL) and arachidonic acid (1.0 or 0.75 mmol/L). Measurements of whole blood parameters were performed to evaluate the three major cell lines in circulating blood.
  
  
  RESULTS
  In patients, platelet count correlated significantly with platelet aggregation (MEA(collagen), p<0.0001; MEA(arachidonic acid), p<0.0001; VerifyNow®, p=0.03). Haematocrit and RBC correlated inversely with MEA induced by collagen (p(haematocrit)<0.001; p(RBC)=0.07) and with VerifyNow® (p(haematocrit)<0.0001; p(RBC)<0.0001), but not with MEA induced by arachidonic acid (p(haematocrit)=1; p(RBC)=0.87). White blood cells correlated significantly with platelet aggregation (MEA(collagen), p<0.001; MEA(arachidonic acid), p<0.0001; VerifyNow®, p=0.05). Similar associations were observed in aspirin-naïve healthy individuals.
  
  
  CONCLUSIONS
  Whole blood aggregometry is dependent on all major cell lines in whole blood. Importantly, platelet aggregation is significantly associated with platelet count even within the normal range.
authors.affiliation: Department of Cardiology, Aarhus University Hospital, Skejby, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Würtz
authors.forename: Anne-Mette
authors.initials: AM
authors.lastname: Hvas
authors.forename: Steen Dalby
authors.initials: SD
authors.lastname: Kristensen
authors.forename: Erik Lerkevang
authors.initials: EL
authors.lastname: Grove
mesh_terms: D000328:Adult; D000368:Aged; D016718:Arachidonic Acid; D001241:Aspirin / Q000627:therapeutic use*; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D003094:Collagen; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000097:blood / Q000000981:diagnostic imaging / Q000188:drug therapy*; D003718:Denmark; D004906:Erythrocyte Count; D005260:Female; D006400:Hematocrit; D006801:Humans; D007958:Leukocyte Count; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D010976:Platelet Count; D010979:Platelet Function Tests; D011237:Predictive Value of Tests; D013997:Time Factors; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D010975:Platelet Aggregation Inhibitors; D016718:Arachidonic Acid; D003094:Collagen; D001241:Aspirin