title: The effect of pre-analytical variables on light transmittance aggregometry in citrated platelet-rich plasma from healthy subjects.
abstract: BACKGROUND
  Although light transmittance aggregometry is considered the gold standard for platelet function testing, it is poorly standardized. The effect of several pre-analytical variables on this assay was investigated.
  
  
  METHODS
  Light transmittance aggregometry was performed with an automated coagulation analyzer using arachidonic acid (1.6 mmol/L), adenosine-5-diphosphate (ADP) (11 μmol/L) and collagen (11 mg/L, all final concentrations). The results were reported as maximum aggregation (in %) in 10 min. Twenty apparently healthy subjects were tested three times on two consecutive days: on day 1, fasting samples were collected in the morning and mid-day; on day 2, samples were collected in the morning after a light breakfast. Light transmittance aggregometry was performed immediately after preparation of platelet-rich-plasma (PRP), after stabilization (30 min) of non-adjusted and platelet count (225-275×10(9)/L) adjusted PRP, and at 2 and 4 h after blood collection.
  
  
  RESULTS
  Maximum aggregation was higher in the non-adjusted compared to the adjusted PRP with all three agonists used (all p<0.05). Arachidonic acid and ADP, but not collagen, induced maximal aggregation was significantly decreased after 4 h (arachidonic acid from 84%, 73%-90% to 71%, 28%-85%, p<0.001; ADP from 79%, 62%-87% to 66%, 50%-79%, p<0.001, medians with inter-quartile ranges). Short-term stabilization of PRP, consumption of breakfast and sampling at mid-day had no significant effect on maximal aggregation.
  
  
  CONCLUSIONS
  Blood collection and plasma preparation can be simplified by omitting short-term stabilization of PRP and adjustment for platelet count. The subjects can be tested from morning to mid-day, and a light breakfast is acceptable. However, the analyses should not be postponed for more than 2 h if arachidonic acid or ADP are used as agonists.
authors.affiliation: Department of Vascular Diseases, University Medical Centre Ljubljana, Ljubljana, Slovenia. mojca.stegnar@kclj.si
authors.forename: Mojca
authors.initials: M
authors.lastname: Stegnar
authors.forename: Anja
authors.initials: A
authors.lastname: Knezevic
authors.forename: Mojca
authors.initials: M
authors.lastname: Bozic-Mijovski
mesh_terms: D001777:Blood Coagulation; D001780:Blood Coagulation Tests / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D010976:Platelet Count; D010979:Platelet Function Tests; D053657:Platelet-Rich Plasma; D012016:Reference Values; D012680:Sensitivity and Specificity