PFA100

PFA-100, or Platelet Function Analyzer-100, is a laboratory instrument used to assess primary hemostasis by measuring the time required for a platelet plug to form and occlude a small aperture under high shear in citrated whole blood. It serves as a rapid screening tool for platelet function and bleeding risk in a variety of clinical settings.

Principle and test cartridges: The device uses disposable cartridges containing a capillary coated with collagen plus either epinephrine (Col/EPI) or adenosine diphosphate (Col/ADP) as agonists. Citrated whole blood is drawn into the cartridge, platelets adhere and aggregate at the collagen surface, and a plug forms to close the aperture. The time to closure, reported in seconds as the closure time (CT), reflects platelet function under flow conditions. Col/EPI and Col/ADP tests interrogate different pathways; Col/EPI is particularly sensitive to the effects of aspirin, while Col/ADP can help reveal defects in ADP-induced aggregation and some von Willebrand disease presentations.

Clinical use: PFA-100 is widely used as a quick screen for platelet function disorders, von Willebrand disease, and the impact of antiplatelet therapy, as well as a preoperative bleeding risk assessment. Abnormal results are not diagnostic and typically prompt confirmatory testing, such as light transmission aggregometry and specific von Willebrand factor assays, interpreted in the clinical context.

Limitations: Closure times are influenced by hematocrit, platelet count, and von Willebrand factor levels, as well as pre-analytical factors like sample handling and time to testing. The test is not standalone diagnostic evidence and can yield false positives or negatives in certain conditions; newer platforms may address some limitations.