Summary
A high on-treatment residual ADP-inducible platelet reactivity in light transmission
aggregometry (LTA) has been associated with an increased risk of adverse outcomes
after percutaneous coronary intervention (PCI). However, LTA is weakly standardized,
and results obtained in one laboratory may not be comparable to those obtained in
another one. We therefore sought to determine the test correlating best with LTA to
estimate clopidogrel-mediated platelet inhibition in 80 patients on dual antiplatelet
therapy after elective percutaneous intervention with stent implantation. We selected
the VerifyNow P2Y12 assay, the vasodilator-stimulated phosphoprotein phosphorylation
assay, multiple electrode platelet aggregometry and the Impact-R for comparisons with
LTA. Cut-off values for residual ADP-inducible platelet reactivity were defined according
to quartiles of each assay. Sensitivities and specificities of the different platelet
function tests were based on the results from LTA. The results from all four assays
correlated significantly with those from LTA. The VerifyNow P2Y12 assay revealed the
strongest correlation (r = 0.61, p < 0.001). Sensitivities and specificities ranged
from 35% to 55%, and from 78.3% to 85%, respectively. In conclusion, although all
assays correlated significantly with LTA, they need to be improved to become clinically
used diagnostic tests. Further, it may be too early to define the gold standard method
for assessing residual ADP-inducible platelet reactivity and generally acceptable
cut-off values.
Keywords
Antiplatelet agents - platelet aggregation - platelet function tests