Platelet aggregation

Biochemistry

SynonymThrombocytes
Platelets
Half-life8 - 12 days
SynthesisIn bone marrow, as pluripotent bone marrow stem cells
Normal range150 000 - 400 000 per μl

Thrombocytes are important for haemostasis and blood vessel repairs. They are also involved in inflammatory reactions. To perform these important tasks, platelets have the capability to interact with structures on the blood vessel walls. They adhere to the vessel wall and aggregate with each other on stimulation, aided by distinct receptors on their cell surfaces. Important receptors are e.g. the glycoproteins Ib/V/IX- and IIb/IIIa-complex.

Clinical significance

The most commonly used method for aggregation assessment is induced thrombocyte aggregation using the Born method. It utilizes platelet rich plasma (PRP) with addition of aggregation inducting substances (inductors) to measure photometric changes in an aggregometer. During aggregation, the light transmission is increased and the change over time is plotted as a curve. From this curve, the following information can be extracted:

  • Maximal light permeability (= mass of aggregated thrombocytes)
  • Aggregation speed
  • Qualitative evaluation of the curve (step shaped, prolonged lag-phase, disaggregation)


The most important inductors are: ADP, collagen, arachidonic acid, epinephrin and ristocetin.

Indication

  • Bleeding tendencies despite a normal thrombocyte count.
  • Support for diagnoses of diseases connected with thrombocytic dysfunction.
  • To differentiate between hereditary bleeding disorders, such as haemophilia A or von Willebrand factor syndrome.
  • Control of acquired bleeding diathesis after ingestion of certain medications.
  • Measuring therapeutic effects of certain medications (compliance).

Literature

  1. Linnemann B, Schwonberg J, Mani H, Prochnow S and Lindhoff-Last E. Standardization of light transmittance aggregometry for monitoring antiplatelet therapy: an adjustment for platelet count is not necessary. J Thromb Haem 6, 677-683, 2008.
  2. Day HJ, Holmsen H. Laboratory Tests of Platelet Function. Ann Clin Lab Sci 2, 63, 1972.
  3. Dacie, Lewis. Practical Haematology. Lewis SM, Bain BJ, Bates I (Editors). 9th Edition, Elsevier Science Ltd. 383-384, 2002.
  4. Consensus-Papier der DGKL-Arbeitsgruppe "Hämostaseologische Labordiagnostik". Blutungsneigung: Diagnostische Strategie zur Abklärung einer Thrombozytendysfunktion. J Lab Med 28, 453-462, 2004.

Test kits

Aggregation reagents

Adenosin-diphosphate (ADP)

Arachidonic acid

Epinephrine

GpIIb/IIIa Antagonist Reagent

Aggregometer

APACT 4004

LPC software for APACT 4004

Cuvettes for APACT 4004

Service Photometer Control Kit

T-TAS® 01