Use of native or platelet count adjusted platelet rich plasma for platelet aggregation measurements

Abstract

Background: It is still not clear whether native or platelet count adjusted platelet rich plasma (PRP) should be used for platelet aggregation measurements.

Aim: To evaluate the necessity of using adjusted PRP in platelet function testing.

Methods: Platelet aggregation with native PRP and adjusted PRP (platelet count: 250/nl, obtained by diluting native PRP with platelet poor plasma) was performed on the Behring Coagulation Timer (BCT(R)) using ADP, collagen, and arachidonic acid as agonists. Healthy subjects, patients on antiplatelet treatment, and patients with thrombocytosis (platelet counts in PRP > 1250/nl) were investigated.

Results: No significant differences in the maximum aggregation response were seen when using either native or adjusted PRP from healthy subjects and patients on antiplatelet treatment. Nevertheless, some patients taking aspirin or clopidogrel showed reduced inhibition of ADP and arachidonic acid induced aggregation in adjusted PRP but not in native PRP. The maximum velocity of healthy subjects and patients on antiplatelet treatment varied significantly as a result of the degree of dilution of the adjusted PRP. Surprisingly, the BCT provided good results when measuring platelet aggregation of native PRP from patients with thrombocytosis, whereas commonly used aggregometers could not analyse platelet aggregation of native PRP in these patients.

Conclusion: The time consuming process of PRP adjustment may not be necessary for platelet aggregation measurements. Moreover, using adjusted PRP for monitoring aspirin or clopidogrel treatment may falsify results. Therefore, it may be better to use native PRP for platelet aggregation measurements, even in patients with thrombocytosis.

Figure 1

Maximum aggregation response using different aggregation agonists. Maximum aggregation response of healthy subjects in per cent on the Behring Coagulation Timer using ADP, collagen (COL), and arachidonic acid (ARA) as agonists. No significant difference was seen using native (dark boxes) or adjusted (light boxes) platelet rich plasma (PRP).

Figure 2

Maximum velocity of the aggregation curve using different agonists. Maximum velocity of the aggregation curve of healthy subjects on the Behring Coagulation Timer using ADP, collagen (COL), and arachidonic acid (ARA) as agonists. A significant difference was seen using native (dark boxes) or adjusted (light boxes) platelet rich plasma (PRP).

Figure 3

Aggregation curves obtained when using native and adjusted platelet rich plasma (PRP). The absolute extinction is decreased when using platelet count adjusted plasma for platelet aggregation measurements.

Figure 4

Typical aggregation curve obtained for patients taking acetylsalicylic acid (ASA). The ADP induced aggregation shows a desaggregation in the curve. The collagen (COL) induced aggregation is not inhibited, whereas the arachidonic acid (ARA) induced aggregation is inhibited by ASA.