Table 2.

Clinically used tests of platelet function and the potential clinical implications of abnormal results.

Test	Information obtained	Potential implications
CBC with peripheral smear	Platelet count Platelet size Platelet granularity	Thrombocytopenia: ITP, marrow infiltration, consumption, DIC Macro-thrombocytopenia: MYH-9, BSS. Micro-thrombocytopenia: WAS Hypo-granularity: Gray platelet syndrome
PFA-100 ®	Closure time for Collagen/ADP or Collagen/Epi	↑coll/ADP alone: ADP receptor disorder ↑coll/Epi alone: Aspirin/NSAIDs, MYH-9 related disorders ↑both: BSS, GT, VWD, Gray platelet syndrome
Platelet aggregation	Aggregation response to various agonists (i.e. ADP, collagen, thrombin, ristocetin)	Impaired ristocetin aggregation: VWD, BSS Impaired aggregation to everything except ristocetin: Glanzmann’s thrombasthenia, afibrinogenemia Primary aggregation only with ADP, Epi, collagen: storage pool disorder
Flow Cytometry	Quantification of platelet surface markers	Low or absent GPIb: BSS Low or absent GPIIb/IIIa: GT Low or absent P-selectin: alpha granule dysfunction
Electron Microscopy	Dense granule content	Low dense granule content: storage pool deficiency

ITP: Immune Thrombocytopenic Purpura, DIC: Disseminated Intravascular Coagulation, BSS: Bernard Soulier Syndrome, WAS: Wiskott Aldrich Syndrome, NSAIDs: Non-Steroidal Anti-Inflammatory Drugs, GT: Glanzmann’s Thrombasthenia, VWD: Von Willebrand disease.