The platelet function analyzer PFA-100® System (Siemens Healthcare Diagnostics) has become a useful tool to detect abnormalities of primary hemostasis in small samples of blood. This test system is a microprocessor controlled instrument which emulates in vitro the platelet dependent phase of primary hemostasis, while delimiting the role of the rheological factors.
Basically, the system monitors platelet interaction on collagen-ADP (COL-ADP) or collagen-epinephrine (COL-EPI) coated membranes. Samples of citrated blood are aspirated under controlled flow conditions (shear rate: 4,000-5,000/s) through a 150 micrometer aperture cut into the membrane. The platelet hemostatic capacity (PHC) in the blood sample is indicated by the time required for the platelet plug to occlude the aperture (closure time), which is expressed in seconds.
The following animation is available for details:
The Platelet Function Analyzer PFA-100® System
Left panel: a series of micrographs showing the closure process. The growing platelet plug progressively blocks the blood flow through the aperture cut. In this case, closure time has taken place at 110 seconds. Right panel: micrograph showing a cross-section view of the occluded aperture cut. A slight layered shape of the plug can be perceived, perpendicular to the blood flow direction. Click on pictures to enlarge.
(Cross-section picture is a courtesy of M. Pino. For image uses, please see Use of Content at Legal Information).
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