Diagnostic Approach for Inherited Platelet Function Disorders

Introduction to Diagnostic Testing

The International Society on Thrombosis and Haemostasis recommends comprehensive platelet function testing, including light transmission aggregometry (LTA) with an expanded panel of agonists, for patients with abnormal bleeding scores and a normal RIPA test 1, 2
The American Society of Hematology suggests that a complete blood count with platelet count and peripheral blood smear should be performed to assess for platelet size and morphology abnormalities 2, 3

Coagulation screening tests, including prothrombin time (PT) and activated partial thromboplastin time (aPTT), should be conducted as part of the diagnostic workup 3
Light transmission aggregometry (LTA) with a standard panel of agonists (ADP, collagen, arachidonic acid, epinephrine, and ristocetin) is a crucial diagnostic test 1, 2
Assessment of platelet granule release (both α and δ granules) is an important aspect of platelet function testing 2, 4
Flow cytometry to analyze major platelet surface glycoproteins (GPIIb/IIIa, GPIb/IX) is a valuable diagnostic tool 1, 5

Inherited platelet function disorders (IPFDs) are heterogeneous in severity, mechanisms, and frequency, with many not yet characterized at the molecular level 2
Patients with IPFDs may experience mucocutaneous bleeding, including easy bruising, epistaxis, menorrhagia, and excessive bleeding following surgery or trauma 6
A normal RIPA test excludes platelet-type VWD and VWD type 2B, which would show enhanced ristocetin-induced platelet aggregation 1, 7

Antifibrinolytic agents like tranexamic acid may be beneficial as adjunctive therapy for patients with IPFDs 8

Many IPFDs have overlapping clinical presentations, making precise diagnosis challenging 1, 2
Preanalytical variables can significantly affect platelet function testing results, including medication use, sample processing, and patient stress level 7
Patients should avoid aspirin and NSAIDs before testing as these can affect platelet function 8, 2
Even with extensive testing, approximately 50% of patients with clinically significant bleeding may remain without a definitive diagnosis and be classified as having a bleeding disorder of unknown cause (BDUC) 8