Abstract 15055: Vasp Measurement by a New Elisa Technique: A Reliable Method, Easier and Faster Than Flow Cytometry
BACKGROUND: Vasodilator Stimulated Phosphoprotein (VASP) measurement is the most specific in vitro evaluation of platelet inhibition in patients treated with a P2Y12 antagonist. Measurements are performed by flow cytometry (FC), a slow and expensive method available only in research units. A new ELISA technique has been developed (BioCytex, Stago) and we sought to compare Platelet Reactivity Index (PRI) obtained by ELISA with PRI measured by FC in coronary patients treated with a P2Y12 inhibitor.
METHODS: VASP-PRI was measured with a Beckman Coulter FC500 cytometer using Platelet VASP kits and simultaneously from the same blood sampling with the ELISA VASP-P technique (Thermo Scientific Multiskan Ascent®). Blood samples from 78 coronary patients, all treated by PCI and P2Y12 inhibitors for 15 days were incubated in vitro with ADP and/or prostaglandin E1 before fixation.
RESULTS: Of the 78 patients, 30 were on clopidogrel 75mg, 5 on clopidogrel 150 mg, 2 on prasugrel 5 mg and 41 on prasugrel 10 mg. The correlations between the 2 techniques were excellent: r = 0.81, r2 = 0.67 p < 0.0001. The area under the ROC curve was 0.91, p<0.0001, when comparing the new ELISA technique with FC to identify non-responders (VASP-PRI >50% with FC) (cf figure 1). Choosing a threshold of 50% for VASP-PRI measured by the ELISA technique provided a Sensitivity (Se) of 63%, a specificity (Sp) of 88% with a Predictive Positive Value (PPV) of 74% and a Predictive Negative Value (PNV) of 82% to identify non-responders (likelihood ratio (LR): 5,67). Choosing a threshold of 55% seems more accurate with a Se of 63%, a Sp of 92%, a PPV of 81% and a PNV of 83% (LR: 16).
CONCLUSION: ELISA VASP measurement provides similar, high quality results, when compared to the reference technique. The 55% threshold seems to be the most relevant. This technique could easily replace FC measurements in daily practice. Figure 1: ROC Curve of VASP ELISA resistant (PRI ≥ 50%) compared to VASP by cytometer
- © 2012 by American Heart Association, Inc.