The Cone-and-Plate(let) analyzer is not suitable to monitor clopidogrel therapy: a comparison with the flowcytometric VASP assay and optical aggregometry.
BACKGROUND
High on-clopidogrel platelet reactivity has been associated with an increased risk for atherothrombotic events. A new player on the horizon is the IMPACT-R ADP-test using ADP pre-stimulation. We here report the results of a thorough evaluation of this new device.


METHODS
The IMPACT-R ADP-test was evaluated in different categories of subjects. First, normal range values were determined in healthy subjects (n=46). Second, the effect of 600 mg of clopidogrel was evaluated with the IMPACT-R ADP-test and two other well-validated methods (flowcytometric VASP-analysis and optical aggregometry) in 21 patients. Third, a head-to-head comparison between the IMPACT-R ADP-test and optical aggregometry was performed in a large cohort of patients on dual antiplatelet therapy.


RESULTS
The results of the IMPACT-R ADP-test were highly variable throughout healthy subjects. The administration of a high clopidogrel loading dose resulted in a small but significant increase in surface coverage but 61.9% of the patients were still identified as clopidogrel nonresponder. In contrast, optical aggregometry and VASP-analysis identified 24% and 33% of these patients as a clopidogrel nonresponder, respectively. Head-to-head comparison with optical aggregometry in 451 patients showed only a modest correlation between both methods (r approximately 0.20, p<0.0001).


CONCLUSIONS
The IMPACT-R ADP-test is relatively insensitive to the effects of clopidogrel and cannot substitute for methods such as flowcytometric VASP-analysis and optical aggregometry. Further studies are required to establish the clinical usefulness of IMPACT-R ADP-test to accurately predict the occurrence of major adverse cardiovascular events in patients with high on-clopidogrel platelet reactivity before it can be implemented in clinical practice.
van Werkum
Jochem W
JW
Department of Cardiology, St. Antonius Hospital, Nieuwegein, the Netherland. w.van.werkum@antonius.net
Bouman
Heleen J
HJ
Breet
Nicoline J
NJ
ten Berg
Jurriën M
JM
Hackeng
Christian M
CM
D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D016022:Case-Control Studies; D015815:Cell Adhesion Molecules; D000077144:Clopidogrel; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008840:Microfilament Proteins; D008875:Middle Aged; D010750:Phosphoproteins; D017949:Retinal Cone Photoreceptor Cells; D013988:Ticlopidine / Q000031:analogs & derivatives; D000098662:Vasodilator-Stimulated Phosphoprotein
D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D000098662:Vasodilator-Stimulated Phosphoprotein; D000077144:Clopidogrel; D013988:Ticlopidine