What are the recommended diagnostic tests and management strategies for Glanzmann thrombasthenia?

Glanzmann Thrombasthenia: Diagnostic and Management Approach

Diagnosis

For suspected Glanzmann thrombasthenia, proceed with a three-tiered diagnostic algorithm starting with blood smear, light transmission aggregometry (LTA) with limited agonists, granule release assessment, and flow cytometry for platelet glycoproteins GPIIb/IIIa (CD41/CD61). 1

First-Step Diagnostic Tests

The initial workup requires approximately 21-28 mL of blood and can diagnose up to 40% of inherited platelet function disorders 1:

• Blood smear examination - Look for altered platelet size or structural abnormalities

• Light transmission aggregometry (LTA) - Test responses to:

  • Epinephrine
  • ADP
  • Collagen
  • Arachidonic acid
  • Ristocetin

  In GT, you will see absent or severely impaired aggregation to all agonists except ristocetin 1

• Flow cytometry on resting platelets - Use antibodies against:

  • GPIIb/IIIa (CD41)
  • GPIIIa (CD61)
  • GPIb (CD42b)
  • GPIb/IX (CD42a)

  GT shows defective expression of GPIIb/IIIa and GPIIIa 1

• Flow cytometry on activated platelets - Use PAC-1 antibody against GPIIb/IIIa activation epitope; GT demonstrates defective activation 1

• Granule release assessment - Measure ATP/ADP secretion via lumiaggregometry or alternative methods 1

Critical pitfall: Do not use PFA-100 or skin bleeding time as these lack sufficient specificity/sensitivity for GT diagnosis 1. A mildly reduced platelet count should not exclude testing for inherited platelet function disorders 1.

Confirmatory Testing

If first-step tests suggest GT, confirm with 2:

• Exon sequencing of ITGA2B and/or ITGB3 genes - GT results from mutations in these genes encoding the αIIbβ3 integrin
• Clot retraction test - Incubate non-anticoagulated whole blood for 60 minutes at 37°C; impaired clot retraction suggests GT 1

GT Classification

Based on flow cytometry findings 2:

• Type 1 GT: <5% of normal GPIIb/IIIa expression
• Type 2 GT: 5-20% of normal GPIIb/IIIa expression

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Management Strategies

Acute Bleeding Episodes

For non-surgical bleeding in GT, use recombinant activated factor VII (rFVIIa) as first-line therapy, which achieves 91% success rate in stopping bleeding, with antifibrinolytics (tranexamic acid) as adjunctive or alternative therapy (84.7% success rate). 3

The treatment hierarchy based on the international GT Registry data 3:

1. Recombinant activated factor VII (rFVIIa) alone: 91.0% treatment success
2. Antifibrinolytics alone (tranexamic acid): 84.7% success
3. rFVIIa + antifibrinolytics: 82.7% success
4. Platelet transfusions ± antifibrinolytics: 78.8% success
5. rFVIIa + platelets ± antifibrinolytics: 72.7% success

Reserve platelet transfusions for situations where rFVIIa fails or is unavailable, as platelet transfusions carry the risk of triggering anti-platelet antibody formation and subsequent platelet-refractory disease 2, 3. The Registry documented 35 adverse events with no thromboembolic events, and only one patient had three possibly drug-related non-serious adverse events (nausea, dyspnea, headache) with rFVIIa 3.

Chronic Management and Prevention

Implement a comprehensive patient blood management strategy to minimize transfusion requirements 4:

• Tranexamic acid - For prophylaxis and treatment of mucocutaneous bleeding
• Hormonal therapy for menorrhagia in female patients:
  • Hormonal contraceptive pills
  • Intrauterine progesterone contraceptive devices
• Iron supplementation - All patients develop iron deficiency from chronic bleeding 4
• Erythropoietin - For anemia management when indicated 4

A Malaysian cohort demonstrated that 70% of GT patients avoided blood transfusions over 5 years using these non-transfusion methods, maintaining mean hemoglobin of 11 g/dL 4.

Emergency Situations

For emergency bleeding, trauma, surgery, or childbirth 5:

1. Immediately administer rFVIIa as first-line hemostatic agent
2. Add tranexamic acid for mucocutaneous bleeding
3. Use platelet transfusions only if rFVIIa fails or in life-threatening hemorrhage
4. Monitor for anti-platelet antibody development if platelet transfusions are required

Curative Options

Bone marrow transplantation remains the only curative treatment, though gene therapy is emerging as a future alternative 2. These should be considered only in patients with severe, life-threatening bleeding refractory to standard therapies.

Clinical Presentation to Anticipate

Patients typically present in early childhood with 2, 4:

• Easy bruising and spontaneous skin bruising
• Mucocutaneous bleeding (epistaxis, gingival bleeding)
• Severe menorrhagia in females (present in all female patients in one series)
• Hemoptysis, hemarthrosis, or hematomas in severe cases
• Mean hemoglobin at diagnosis: 5.6 g/dL due to chronic bleeding 4