PFA-100 platelet function analyzer.
Q What is the Dade Behring PFA-100 platelet function analyzer? What does it measure? What if the patient is on anti-platelet drugs? What is its application in head trauma injury?
A The Dade Behring PFA-100 platelet function analyzer is used to evaluate primary hemostasis hemostasis /he·mo·sta·sis/ (he?mo-sta´sis) (he-mos´tah-sis)
1. the arrest of bleeding by the physiological properties of vasoconstriction and coagulation or by surgical means.
2. in citrated whole blood. It measures ex vivo ex vivo /ex vi·vo/ (eks´ ve´vo) outside the living body; denoting removal of an organ (e.g., the kidney) for reparative surgery, after which it is returned to the original site. platelet binding to collagen/epinephrine (CEPI) or collagen/adenosine diphosphate di·phos·phate
An ester of phosphoric acid containing two phosphate groups. (CADP CADP Construction and Analysis of Distributed Processes
CADP Coalition Against Database Piracy
CADP Collagen-Adenosine Diphosphate
CADP Central Area Data Processing
CADP Coordinator for Automatic Data Processing
CADP Cooperative Antenna Development Program ). It contains a high-shear flow system to allow blood to pass through a membrane with an aperture. The membrane is coated with collagen fibrils and one of activators epinephrine or ADP (1) (Automatic Data Processing) Synonymous with data processing (DP), electronic data processing (EDP) and information processing.
(2) (Automatic Data Processing, Inc., Roseland, NJ, www.adp. (adenosine diphosphate). The platelet activation occurs as blood flows through the aperture. When citrated whole blood mixes with activators, platelets start to form aggregates. The time taken for blood to form a platelet plug that occludes the aperture is an indication of platelet function and is referred to as the closure time (CT). PFA-100 is only a screening test to determine whether abnormal platelet function is present in the patient. There is no critical value at which you can predict whether the patient will bleed in the surgery. If the patient is on an anti-platelet drug, you can only say that the patient's platelet function is compromised due to drugs, using PFA-100, but you cannot predict the bleeding tendency.
Von Willebrand Factor von Willebrand factor (vWF)
A protein found in the blood that is involved in the process of blood clotting.
Mentioned in: Von Willebrand Disease
von Willebrand factor , or vWF, is the key adhesive protein that mediates platelet adhesion and aggregation in the PFA-100 test cartridge. CT is highly sensitive to von Willebrand disease Von Willebrand Disease Definition
Von Willebrand disease is caused by a deficiency or an abnormality in a protein called von Willebrand factor and is characterized by prolonged bleeding. , or vWD. CT is also highly sensitive to qualitative and quantitative defects to platelet receptors that mediate adhesion and aggregation. Thus, CT is also sensitive to inherited or acquired defects in platelet function. If aspirin is the cause of platelet dysfunction, however, only the CT of collagen/epinephrine will be prolonged but not collagen/adenosine diphosphate.
Other factors affecting the CT include low hematocrit Hematocrit Definition
The hematocrit measures how much space in the blood is occupied by red blood cells. It is useful when evaluating a person for anemia.
Blood is made up of red and white blood cells, and plasma. (<35%) or low platelet counts (<150,000/mL). In these situations, the prolonged CT may not reflect abnormal function of platelets. Bleeding time (BT) was designed to evaluate platelet function. BT, however, is very imprecise with a high degree of variation. Currently, PFA-100 has almost replaced BT in evaluating platelet function for pre-surgical screening. Abnormal hemostasis is associated with trauma-related morbidity and mortality Morbidity and Mortality can refer to:
--Min Xu, MD, PhD
Department of Laboratories
Children's Hospital and Regional Medical Center
1. Kundu SK, et al. Description of an in vitro platelet function analyzer--PFA-100. Semin Thromb Hemost. 1995;21(suppl 2):106-112.
2. Jacoby RC, et al. Platelet activation and function after trauma. J Trauma. 2001;51(4): 639-647.