Do patients with thromboembolic disease have circulating platelet aggregates?

Area of Science:

• Hematology
• Vascular Biology
• Thrombosis Research

Background:

• Circulating platelet aggregates (microemboli) are implicated in thromboembolic and vascular disorders.
• The standard Wu and Hoak method (1974) measures these aggregates by comparing platelet counts in blood fixed with formaldehyde versus dispersed with EDTA.
• This method assumes aggregates are solely formed in vivo.

Purpose of the Study:

• To compare the standard Wu and Hoak technique with modified blood collection methods for detecting platelet aggregates.
• To investigate whether platelet aggregate formation occurs artifactually during venipuncture.
• To reassess the concept of chronic microembolism in patients with thromboembolic disorders.

Main Methods:

• Comparison of three methods: standard Wu and Hoak, modified direct syringe draw, and whole blood platelet counting.
• In vitro validation using adenosine diphosphate (ADP) to induce platelet aggregation.
• Evaluation in 12 healthy subjects and 37 patients with thromboembolic disorders, including a subset with myocardial infarction.

Main Results:

• Both modified techniques successfully detected in vitro platelet aggregates.
• In normal subjects, all three methods yielded comparable results.
• In patients with thromboembolic disorders, the standard Wu and Hoak method reported lower aggregate ratios compared to modified techniques.
• Heparin treatment did not affect the results.

Conclusions:

• Platelet aggregate formation may occur artifactually during venipuncture, particularly in patients with thromboembolic disease.
• Platelet hyperactivity in these patients might contribute to in vitro aggregate formation during blood collection.
• The clinical significance of chronic microembolism in thromboembolic disorders requires re-evaluation given potential collection artifacts.