Platelet Aggregation Test

  


1. Objective

The objective of this test was to evaluate the functionality of platelets by measuring their ability to aggregate in response to various agonists.

2. Principle

The test was based on the principle that platelets, when exposed to aggregating agents (agonists), clump together. This aggregation caused a change in light transmission through platelet-rich plasma (PRP), which was measured by an aggregometer. A functional platelet population exhibited a characteristic response to each agonist.

3. Materials Used

  • Patient’s citrated blood

  • Centrifuge

  • Platelet aggregometer

  • Aggregating agents: ADP, collagen, epinephrine, arachidonic acid, ristocetin

  • Cuvettes and stir bars

  • Pipettes

4. Procedure

  1. Blood was collected in a citrate tube and centrifuged at low speed to obtain PRP.

  2. The remaining blood was centrifuged at higher speed to prepare platelet-poor plasma (PPP) for use as a blank.

  3. PRP was added into a cuvette with a magnetic stir bar and placed in the aggregometer.

  4. A known amount of an agonist was added.

  5. Light transmission was recorded over time.

  6. The procedure was repeated with different agonists.

5. Result Interpretation

  • Normal: Platelets showed typical aggregation curves with all standard agonists.

  • Abnormal: Reduced or absent aggregation with specific agonists indicated disorders such as:

    • Glanzmann thrombasthenia (no aggregation with ADP, collagen, epinephrine; normal with ristocetin)

    • Bernard-Soulier syndrome (normal with ADP and collagen; abnormal with ristocetin)

    • Aspirin effect (impaired response to arachidonic acid or epinephrine)

6. Clinical Use

This test was used to diagnose inherited or acquired platelet function disorders and to assess the effect of antiplatelet medications.

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