ITC VerifyNow System Platelet Reactivity Test - Manual (Page 7)

Page 3 14439.C 03/2013
Introduction - 1
VerifyNow System User Manual | USA
1 Introduction
Before you begin to use the VerifyNow System, it is appropriate to review the purpose of the test.
1.1 Platelet Function Testing
In general, platelet function testing measures the activity of platelets. Therapies that inhibit platelet function have
been used extensively to prevent the clinical complications of atherothrombosis. Three classes of potent anti-
platelet agents, including acetylsalicylic acid (aspirin), P2Y12 inhibitors (e.g. thienopyridines), and glycoprotein
(GP) IIb/IIIa inhibitors, have been developed.
The VerifyNow System detects platelet activity by measuring in vitro platelet aggregation in a blood sample
exposed to specific agonists. This includes inhibition of platelet activity in response to anti-platelet therapies.
The VerifyNow ® System is a whole blood, point-of-care test, which measures platelet-induced aggregation as an
increase in light transmittance. It consists of a turbidimetric-based optical detection instrument, single-use test
devices, and associated quality controls ( Figure 1-1 ).
There are three types of VerifyNow tests: Aspirin, PRUTest, P2Y12, and IIb/IIIa (specifically for monitoring of
abciximab or eptifibatide). Each test device contains a lyophilized preparation of human fibrinogen coated beads
and a platelet agonist. The platelet agonist varies by test type. Each test is based upon the ability of GP IIb/IIIa
receptors on activated platelets to bind to fibrinogen-coated beads. When the activated platelets are exposed to
the fibrinogen-coated beads, aggregation occurs in proportion to the number of available platelet receptors. The
instrument is designed to measure this aggregation as an increase in light transmittance. The following sections
describe the mechanism of action for the three tests. Refer to Chapter 2, Overview of System Components for
more information on the instrument and consumables.
It should be noted that GP IIb/IIIa inhibitors such as abciximab (ReoPro ® ), eptifibatide (Integrilin ® ) and tirofiban
(Aggrastat ® ) interfere with the VerifyNow ® Aspirin Test and PRUTest. Patients who have been treated with
Glycoprotein IIb/IIIa inhibitor drugs should not be tested with the VerifyNow Aspirin Test or PRUTest until platelet
function has recovered. This time period is approximately 14 days after discontinuation of drug administration for
abciximab (ReoPro) and up to 48 hours for eptifibatide (Integrilin) and tirofiban (Aggrastat). The platelet function
recovery time varies among individuals and is longer for patients with renal dysfunction. Results obtained from
patients tested prior to platelet function recovery may be inconsistent and unreliable.
The following sections describe the mechanism of action for the three tests. Refer to Chapter 2, Overview of
System Components for more information on the instrument and consumables.
Figure 1‑1 VerifyNow System