PFA-200 :: Platelet Function Analyser

An automated analyser assesses primary haemostasis under shear stress.

Two cartridges:

  • CEPI: collagen and epinephrine (adrenaline).
  • CADP: collagen and ADP

Blood sample is aspirated through the cartridge membrane – leading to platelet activation and aggregation.  The time to close the membrane aperture (closure time) is measured.

Aggregation depends on adequate platelet numbers, and platelet functional ability (vWF, platelets GP Ib, GP IIb/IIIa and fibrinogen).

Variables affecting results:

  • Collection Time: Assay within 4 hours of collection.
  • Haematocrit: Anaemia increases closure time (Hct <20%).
  • Platelet Count: Closure times increase as plate count<100.
  • Blood group/vWF levels
  • Drugs: Aspirin, NSAID, clopidogrel (variable)
  • Acquired platelet function defects: cardio-pulmonary bypass, liver disease, renal failure.

PFA-200 patterns

Glanzmann’s;  Bernard Soulier
Storage Pool DefectN (or ↑)
Renal Failure, MPD, CABG

Platelet aggregation studies

Tests the ability of certain agonists (stimulants) to produce platelet clumping or aggregation.

Patterns of abnormality can help identify the type of platelet defect.

Common defect patterns:

DisorderDefectPlat CountBlood FilmADP 2uMADP 5-10uMCollagen 1ug/mLAA 100uMAdrenaline 10UMRisocetin 1.2mg/mL
Aspirin/NSAID  Inhibit COXNN1Y wave no 2y wave1y
no 2y
ADP antagonists (clopidogrel)Inhib ADP receptorNNAbsentAbsentNNNN
Glanzmanns’s ThrombastheniaGpIIb/IIIa receptorNNAbsentAbsentAbsentAbsentAbsentN
Bernard Soulier SyndromeGpIb-V-IX receptorGiant plats ê platNNNNNAbsent
Gray Platelet Syndromeα-granule deficGray platsN/↓N/↓N/↓NNN
Dense Granule Deficiencyδ-granulesNNNAbsentNNo 2y wave? 1Y only
VWD Type IIbVWF protein NNNNNN  
↑ 0.5 risto
Platelet type vWDMutn GpIb receptor NNNNNN  
↑ 0.5 risto
Renal FailureAcquired SPDN/↓ NN/↓N/↓N/↓
Liver Disease N/↓ 1Y only1Y only?1Y onlyN/↓
Afibrinogenaemia   AbsentAbsentAbsent Absent 

Strong agonists: collagen, thrombin, TXA2 – directly induce plat agg, TX synthesis and plat gran secretion.

Weak agonists: ADP, Adren: Induce platn agg without secretion. (biphasic curve)


ADPLD:1–5 uM HD 10uMADP binds ADP receptor on plat. Shape change – 1y agg. 2y wave = ADP from plat storage grans. LD –> 1y only. 2y wave inhib by aspirin and NSAIDs. Clopidogrel inhibs P2Y1 receptor
Collagen1, 4ug/mLCollagen binds GpVI and GpIa/IIa inducing granule release, TX and GPIIb/IIIa activn. Lag phase.
RistocetinLD: 0.5mg/mL HD: 1.5-5mg/mLRistocetin (not LD) cuases plats agglutination (not agg) via vWF abd GP1b-IX-V complex.
Adrenaline5,10uMAdrenaline blinds a2 recepotor on plat — Ca release. Similar to ADP agg. 1y , 2y wave with ADP released from grans. 2y wave inhib by aspirin,. NSAIDs.  Variation in a receptor density – reduced agg.
Arachadonic Acid500ug/mLAA is precursor to TXA2. Via cyclo-oxygenase and thromboxane synthase.  TX is potent plat activator