QUALITATIVE PLATELET DISORDERS

Qualitative Platelet Disorder

• Functional platelet disorder

• Platelet count – Normal

Causes

• Inherited

Level Affected	Defect	Disorder
Adhesion	Gp Ib–IX defect ↳ Bernard–Soulier syndrome vWF defect ↳ von Willebrand disease	• Abnormal PFA • RAT Negative
Activation	Alpha granule defect ↳ Grey platelet syndrome Delta granule defect ↳ Hermansky–Pudlak syndrome	• RAT Positive • Secondary wave of aggregation ↳ Waves partially normal
Aggregation	Gp IIb–IIIa defect ↳ Glanzmann thrombasthenia	• RAT Positive • Secondary wave of aggregation ↳ Absent/defective waves

• Acquired
• Most common – Uremia
• Others – Drugs

DIAGNOSTIC APPROACH

Bleeding can be due to	Features
Platelet issue	Small bleed like Mucosal bleed
Clotting factor	Hematoma, joint bleed

1. Number

• Thrombocytopenia
• A/c → Child < 6m
• C/c → Old > 6m

2. Function

• PFA 100 analysis
• Platelet function analysis
• Best Screening Test
• Calculates aperture closing time
• (time for platelets to form a clot)
• Platelet Fault analysis
• (If prolonged → Defective platelet function)
• -ve → Normal (<80sec)
• +ve → Abnormal (>80sec)

If Abnormal PFA → RAT

• Ristocetin Agglutination Test

• Check adhesion: Adhesion factor
• Negative
• Adhesion defect → vWF, BS
1. Add plasma
• Normalise → vwF (due to gain of factor 8)
2. Check APTT
• ↑↑ → vwF
• Normal → BS
• Positive
• Normal adhesion
• So check aggregation

If RAT Positive → Secondary wave of aggregation

• Absent/defective waves → Aggregation defect → GT

• Waves partially normal → Activation defect → GP, HP

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Level Affected	Defect	Disorder
Adhesion	Gp Ib–IX defect ↳ Bernard–Soulier syndrome vWF defect ↳ von Willebrand disease	• Abnormal PFA • RAT Negative
Activation	Alpha granule defect ↳ Grey platelet syndrome Delta granule defect ↳ Hermansky–Pudlak syndrome	• RAT Positive • Secondary wave of aggregation ↳ Waves partially normal
Aggregation	Gp IIb–IIIa defect ↳ Glanzmann thrombasthenia	• RAT Positive • Secondary wave of aggregation ↳ Absent/defective waves

Feature	BSS	Glanzmann
Defect	Gp Ib–IX	Gp IIb–IIIa
Key Features	Large platelets	ㅤ
Problem	Adhesion defect (Ristocetin)	Aggregation defect (ADP / Collagen)
Bleeds	Platelet bleeds	Severe bleeding  ↳ Recurrent episodes ↳ Heavy menstrual bleeding

NOTE

• Blue → Normal sample

• Red → Patient sample

Plasma Used	Test
PRP – Platelet-Rich Plasma	• Platelet aggregation studies
PPP – Platelet-Poor Plasma	• PT / APTT / coagulation studies • Reference for 100% light transmission in Platelet aggregation

Platelet Aggregometry/ Waves of Aggregation

• Principle is always Optical light transmission.

• Assesses platelet function

• Uses Platelet-Rich Plasma (PRP).
• PRP has many free platelets.
• Low light transmittance.

• When Agonists added:
1. Ristocetin
2. ADP
3. Epinephrine
4. Collagen

• Effect
• Platelets aggregate
• ↑ Aggregation → ↑ Light transmission.
• Defective aggregation → ↓ Light transmission.

Key Takeaway