Estimating short- and long-term reference change values and index of individuality for tests of platelet function

Clin Biochem. 2019 Dec:74:54-59. doi: 10.1016/j.clinbiochem.2019.10.001. Epub 2019 Nov 4.

Abstract

Background: In order to manage risks of bleeding and thrombosis after some surgical procedures, platelet function is often measured repeatedly over days or weeks using laboratory tests of platelet function. To interpret test results in the perioperative period, it is necessary to understand analytical, biological and between-person variation.

Methods: We collected three separate blood specimens from 16 healthy volunteers on the first study day, and one additional specimen from each volunteer 1, 2, and 3 months later. Arachidonic acid-induced and adenosine diphosphate (ADP)-induced platelet function were measured in duplicate by whole blood impedance aggregometry using Multiplate (ASPI/ADP tests) and VerifyNow (Aspirin Reaction Units [ARU] and P2Y12 Reaction Units [PRU]). The analytical variation (CVA), within-subject variation (CVI), between-subject variation (CVG), index of individuality (II), and reference change values (RCV) were calculated.

Results: VerifyNow ARU demonstrated the smallest short-term and long-term variability (CVA, CVI, and CVG ~1%), resulting in short- and long-term RCV values <5%. II was also higher (1.92) for VerifyNow ARU than other platelet function tests. Multiplate ASPI and ADP tests had the highest RCV both short-(19.0% and 25.2%, respectively) and long-term (32.1% and 39.6%, respectively) due to increased CVA (>5%) and CVI (3.9-13.1%). VerifyNow PRU had a lower RCV than Multiplate ADP; but was the only test with II <0.6.

Conclusions: VerifyNow ARU results can be interpreted relative to a fixed cut-off or population-based reference interval; or relative to small changes in an individual's previous values. VerifyNow PRU and Multiplate ASPI and ADP tests should only be interpreted based upon relative change; and can only distinguish relatively large (>23%) changes over several weeks.

Keywords: Biological variation; Index of individuality; Platelet function test; Relative change value.

MeSH terms

  • Adenosine Diphosphate / pharmacology
  • Arachidonic Acid / pharmacology
  • Aspirin / pharmacology
  • Biological Variation, Population / physiology*
  • Female
  • Follow-Up Studies
  • Hemorrhage / prevention & control
  • Humans
  • Male
  • Normal Distribution
  • Platelet Aggregation / drug effects
  • Platelet Aggregation Inhibitors / pharmacology
  • Platelet Function Tests*
  • Reference Values
  • Thrombosis / prevention & control

Substances

  • Platelet Aggregation Inhibitors
  • Arachidonic Acid
  • Adenosine Diphosphate
  • Aspirin