Preliminary Data from a Field Trial of the PFA-100™ System

Abstract

The PFA-l()O'!!!l system* (Oade International [ne., Miami, FL) is a platelet function anaIyzer, the design of which is based on the technology of the Thrombostat 4000 VDG, Seton, Germany.t It was developed to measure primary, platelet dependent hemostasis in citrated whole blood in vitro. A first pilot study was conducted with the instrument to assess performance characteristics. Healthy subjects (normals) who had not ingested any medications, and patients (abnormals) with primary, platelet-related hemostasis defects, which included users of aspirin, were studied with two test cartridges; collagen/ADP and collagen/epinephrine. Before the study certain variables were tested that ascertained that blood drawn into either 3.8% or 3.2% sodium citrate containing vacutainers (rather than syringes) could be used for testing. Tests must be performed within a five-hour time span from drawing to testing, and blood must be kept at room temperature. Normal reference nlues were 77-133 seconds closure limes for collagen/ADP and 98-185 seconds for collagen! epinephrine. Precision testing revealed a CV of <10% for within-day and between-day (five days) analyses on collagen/ADP cartridges and a CV of 5-14% for both runs on the collagen/epinephrine cartridges. No clinically important differences were found between measurements in the two positions of the instrument, although one follows the other. Tests on 99 normals and 70 abnormals were performed and data expressed as receiver/operator characteristics (ROC) curves that assess the combined sensitivity and specificity of a procedure. An area under the curve of 1.0 means that all samples (normals + abnormals) were accurately identified; a value of 0.5 indicates that the test is noninformative. Using collagen/ADP cartridges a value of 0.76 was found when testing 99 normals and 52 abnormals. All aspirin users had been omitted from the abnormals. With the cOllagenl epinephrine cartridges, evaluating 99 normals and 70 abnormais, a value of 0.89 was obtained. This analysis entailed also aspirin users. Of 24 known aspirin users the collagen!epinephrine cartridges identified 20 that had normal closure times with the collagen! ADP cartridges. Three aspirin users had abnormal values with both cartridges, one subject was normal with both. When the traditional Ivy bleeding times were plotted as an ROC curve, an area under the curve of 0.698 was found. The data suggest that the PFA-I()OtSl system identifies normals and abnormals (subjects with primary, platelet related hemostasis derects) with greater sensitivity and specificity than the present widely used bleeding time. The instrument is easy to use and could be adapted 10 routine laboratory use. The data presented are preliminary and need to be confirmed by additional testing.

Enhanced ex vivo inhibition of platelet function following addition of dipyridamole to aspirin after transient ischaemic attack or ischaemic stroke: First results from the TRinity AntiPlatelet responsiveness (TrAP) study

“…The time taken for activated platelets to occlude an aperture in the cartridge is called the closure time; the maximum closure time recorded by the device is 300 s, and we arbitrarily defined closure times >300 s as 301 s (McCabe et al, 2005b). Aspirin prolongs C-EPI closure times in 83-100% of healthy controls, (Kundu et al, 1994;Mammen et al, 1995Mammen et al, , 1998Harrison et al, 1999) with minimal prolongation of C-ADP closure times in 0-24AE2% of healthy controls (Mammen et al, 1995(Mammen et al, , 1998Harrison et al, 1999). To our knowledge, longitudinal studies assessing the impact of adding dipyridamole to aspirin in individual patients following TIA or ischaemic stroke have not been performed on the PFA-100.…”

Use of a novel platelet function analyzer (PFA-100?) with high sensitivity to disturbances in von willebrand factor to screen for von willebrand's disease and other disorders

“…The test principles and characteristics of this instrument have been previously outlined [14][15][16]. In brief, the PFA-100™ uses blood flow through a capillary device to mimic high shear stress conditions that occur in-vivo (i.e., "simulates" primary hemostasis).…”

Failure of Platelet Parameters and Biomarkers to Correlate Platelet Function to Severity and Etiology of Heart Failure in Patients Enrolled in the EPCOT Trial

“…Precision testing is reported to show a coefficient of variation of ! 10% for within-day and between-day analyses on collagen/ADP cartridges and 5-14% for collagen/epinephrine cartridges [16]. Collagen/epinephrine cartridges are reported to show qualitative platelet defects, such as acetylsalicylic-acid-induced abnormalities, while collagen/ADP cartridges show thrombocytopathies but not qualitative platelet abnormalities.…”