Over the next four weeks, this blog will be previewing upcoming AABB 2018 abstracts that feature ThromboLUX.
This post covers two abstracts that came out of one study. The data set generated during a randomized controlled trial conducted at Vancouver General Hospital (VGH) from 2011 to 2014 under the guidance of Dr. Kate Chipperfield was analyzed retrospectively, with a focus on HLA matching of platelets and in vitro characterization of platelet transfusions. The study enrolled 200 hematology-oncology patients with informed consent. The primary goal of the study was to investigate the effect of platelet activation status as determined by microparticle (MP) content on transfusion outcome.
Poster Number IGT61:
Could Avoiding Activated Platelets Improve the Success Rate of HLA Matched Transfusions?
Up to 35% of patients who depend on platelet transfusion support become refractory to platelets, yet only a very small proportion of this refractoriness can be attributed to alloimmunization (primarily HLA antibody mediated). The primary treatment for refractoriness is to transfuse HLA-matched platelets, however, only about 26% of these transfusions result in adequate count increments.
In this abstract, Dr. Chipperfield and Dr. Maurer investigate the possibility that platelet activation status affects the success of HLA matched platelet transfusions. The clinical response to activated platelets and non-activated platelets was compared for all HLA-positive and HLA-negative study patients. Of the 200 patients, 21 were HLA-positive, of which 13 became refractory.
This investigation found that when patients received non-activated, non-HLA-matched platelets, the 1-hour corrected count increments (CCI) were significantly lower for HLA-positive patients compared to HLA-negative patients: 8.3±8.8 vs. 14.3±8.1 (p=0.002 at 95% significance level). Due to study logistics, only one patient received HLA-matched platelets with known platelet activation status. In this special case, the patient received 11 unsuccessful non-HLA-matched platelet transfusions, followed by two unsuccessful activated, HLA-matched platelet transfusions. The next three transfusions used non-activated, HLA-matched platelets, and resulted in adequate platelet recovery and survival at which point the patient was discharged.
Dr. Chipperfield and Dr. Maurer’s conclusion is that for HLA-positive patients selecting non-HLA-matched platelets for transfusion did not achieve sufficiently high 1-hour CCIs even when the platelets were non-activated. However, transfusing non-activated, HLA-matched platelets restored both 1-hour and 24-hour CCIs in one alloimmunized patient.
For additional details on this study visit poster IGT61 on Sunday, October 14, 1:00 pm – 2:00 pm in the Boston Exhibition & Convention Center (BCEC) Hall A
Poster Number NIT32:
Why Are in Vitro Platelet Characteristics Not Predicting Clinical Outcomes?
There has long been a desire in transfusion medicine to find an in vitro assay that is able to accurately predict what will happen following a transfusion in vivo. This is especially of interest for platelet transfusions because one in six platelet transfusions fails to achieve the desired outcome. Numerous assays have been developed; however, none have been implemented in hospital blood bank practice for routine platelet inventory management.
In this abstract, Dr. Maurer describes a comparison between microparticle (MP) content with morphology score and clinical outcome with the goal of revealing the challenges of developing a predictive assay and informing future studies. The primary result was a moderate correlation between MP content and 24-hour corrected count increments (R2 = 0.304, P = 0.018). Additionally, for activated platelets, a moderate inverse correlation was found between MP content and morphology score (R2 = 0.315, P = 0.001). However, for non-activated platelets, no correlation could be found due to an inability to differentiate non-activated platelets by visual inspection.
The main conclusion of this abstract is that platelet transfusions have a high probability of an insufficient increase in 24-hour CCI if they have MP content greater than 15% or a low morphology score. Thus, a practical approach for improving overall clinical outcomes may be to avoid activated platelet transfusions for prophylaxis.
Dr. Maurer also concluded that MP content and morphology score have an advantage over relative quality control parameters because MP content and morphology reflect the entire history of platelets from the donor to the final platelet unit. Additionally, while these two assays are unable to predict all outcomes they do appear to be useful in predicting the worst outcomes.
For additional details on this study visit poster NIT32 on Sunday, October 14, 1:00 pm – 2:00 pm in the Boston Exhibition & Convention Center (BCEC) Hall A
You can hear the results from another four ThromboLUX studies by attending our workshop at AABB the morning of October 15th or by visiting us in the exhibit hall at Booth 724.