PFA100 closure times

Last updated: Tuesday, 07, August, 2007

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Item	Process
Specimen	5 mL blood collected into citrate anticoagulant.
Method	Citrated blood is aspirated under high shear, through a capillary tube onto a collagen/ADP (CADP) coated membrane, or a collagen/epinephrine (CEPI) membrane containing a 150 µm diameter central aperture. Platelet aggregation eventually produces total closure of the aperture and the time until this occurs is measured. Test must be performed on whole blood (that is non-centrifuged) within 4 hours of collection. The result is only valid in an individual with a normal platelet count.
Reference Interval	Guide only, may be laboratory specific: 71-118 seconds for CADP 85-165 seconds for CEPI.
Application	PFA100 testing provides a broad screening test of platelet function. It is sensitive to abnormalities of platelet function, as well as thrombocytopenia, and is also sensitive to defects or deficiencies in VWF (that is VWD).
Interpretation	A normal test result (CEPI) will exclude most significant platelet function related defects including severe VWD. A prolonged CEPI with normal CADP is consistent with any of the following: mild throbocytopaenia; low haematocrit; mild platelet dysfunction; mild VWD; or may be related to recent antiplatelet medication including aspirin. A prolonged CEPI and CADP is consistent with any of the following (or combination thereof): thrombocytopaenia; low haematocrit platelet dysfunction VWD; or recent antiplatelet medication. An abnormal PFA result needs to be followed up - consult laboratory. See also Platelet function studies.
Reference	P Harrison et al. Clin Lab Haem 2002; 24: 225-232. Carcao MD et al. Br J Haematol 2002; 117: 961-964. Favaloro EJ. Haemophilia 2001; 7:170-179. Favaloro EJ. Curr Opin Haematol 2002; 9: 407-415.