CytogeneticsPlatelet inhibition testing: whole blood point-of-care vs traditional platelet aggregometry

Abstract

Abstract Monitoring drug response to ensure optimal platelet suppression is necessary in select patients on dual antiplatelet therapy (DAPT). At our institution, responses to aspirin (ASA) and P2Y12 inhibitors (P2Y12-Is) are assessed by light transmission aggregometry (LTA) using the Helena AggRAM assay. This method requires platelet-rich plasma (PRP) and is labor intensive. Platelet mapping using thromboelastography (TEG) is an alternate method, which offers point-of-care testing on whole blood. Here, we aimed to evaluate the concordance of our LTA assay with TEG, as well as the VerifyNow® PRUTest. We aimed to run testing on at least 20 patient samples; however, at the time of abstract submission, only 10 samples were available. Ten blood samples from 8 patients on dual anti-platelet therapy were collected in preparation for neurologic stent placement. Prepared PRP was analyzed by LTA on the Helena AggRAM assay. The maximal amplitude of the aggregation curves was recorded in the presence of high dose (HD) ADP, low dose (LD) ADP, and arachidonic acid (AA). Whole blood was analyzed by TEG using PlateletMapping ADP & AA assay cartridges on the Haemonetics® TEG 6s analyzer, and by the VerifyNow® PRUTest. Thresholds to qualify platelet suppression as optimal or suboptimal were defined a priori following established guidelines. Concordance between methods was calculated using the following formula: (optimal/optimal + suboptimal/suboptimal) / total number of samples. Pearson correlation between units of measure was also determined. For P2Y12-I response, concordance between LTA and TEG was 70% (correlation was r = 0.76 between TEG and LTA with HD ADP, and r = 0.70 between TEG and LTA with LD ADP). Concordance between VerifyNow® and LTA was 60% (correlation was r = 0.84 between VerifyNow® and LTA with HD ADP, and r = 0.78 between VerifyNow® and LTA with LD ADP). Finally, concordance between VerifyNow® and TEG was 30% (correlation was r = 0.81). Regarding ASA response, concordance was 80% between LTA and TEG (correlation was r = 0.31). To summarize, overall concordance ranged from 30 to 80% across platforms. For P2Y12 inhibition, results obtained from LTA with HD ADP and VerifyNow® had the strongest correlation (r = 0.84). Interestingly, the correlation between VerifyNow® and TEG was similarly elevated (r = 0.81), but concordance was poor (30%). When comparing TEG to LTA, the strongest correlation was between LTA with HD ADP and TEG (r value = 0.76). Concerning ASA inhibition, concordance between LTA and TEG was acceptable; however, correlation was weak (80%; r = 0.31). Results from this preliminary study support the potential use of TEG to monitor platelet response to therapy. We plan to continue our testing to include a minimum of 20 samples, and also consider patient outcomes, before implementing any laboratory workflow changes.