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We have found that hospitals with a higher percentage of activated platelets in their inventory use more platelets per patient. Platelet activation is a normal part of the platelet life cycle and platelets can become activated from a wide variety of sources. Some of these activation sources are related to the collection and handling methods used by the blood supplier. Therefore, we decided to investigate the activation rates from the wide range of platelet suppliers that our study partners have tested.

Investigating Activation Rates

For the purpose of this post, we only analyzed suppliers with at least 50 platelet units tested on ThromboLUX. Nine suppliers meet this criterion. The average activation rate among those nine suppliers was 30% with a range of 49% to just 15%, as shown in the figure below.

This national average was calculated by taking the unweighted average of the nine suppliers with data available. Therefore, this average does not represent the chances that an individual platelet unit is activated, rather it provides a value to benchmark individual suppliers against.

These nine suppliers are further characterized in the figure below by listing what type of supplier they are (national scale, regional, community, or hospital-based collection facility). The figure below also lists the apheresis collection machine used by the supplier as determined from direct communication with the supplier or the hospital that receives blood from the supplier. Only the national scale supplier uses the Amicus apheresis system, five suppliers use the Trima Accel apheresis system, and 3 suppliers’ apheresis technology could not be determined. The number of samples tested for each supplier is also listed.

An additional data point of interest is the consistency of the activation rate for the national blood supplier across the hospitals it supplies. Four different sites tested at least 50 platelets from the national blood supplier. These four sites are spread across the US. As the figure below shows, the activation rates varied only slightly between sites.

Hypotheses for the Differences in Platelet Activation Rates

One possible hypothesis could be that extended shipping distances of the national supplier may play a role in their high activation rate, however, this seems unlikely based on previous findings that transportation seems to have minimal impact on platelets and platelet activation [1] [2], Furthermore, the supplier with the lowest activation rate had the majority of their platelets shipped across the country suggesting that transportation is not causing platelet activation in the final product.

An alternative hypothesis is that the apheresis technology plays a major role in determining activation rates. There are some reports in the literature that show reduced corrected count increments and increased P-selectin measurements from Amicus collected platelets [3][4]; therefore, increased platelet activation rate in the suppliers using the Amicus system would not be surprising. However, due to the limited number of suppliers that use the Amicus system in this data set it cannot be determined if the apheresis technology played a major role in platelet activation.
A final hypothesis is that the donor population between the suppliers is the primary factor in determining the platelet activation rate. Conditions within the donor are the primary factors determining whether an individual platelet bag is activated or not [1]. It is possible that the differences between the regional and community scale suppliers is explained by locations with elevated rates of asthma, diabetes, depression and a host of other conditions that may lead to activated platelets, but do not lead to donor deferral. This hypothesis is yet to be fully investigated.

Discussion and Future Directions

There is much more work to be done to better understand what leads to increased platelet activation rates for certain suppliers. The apheresis technology may explain a portion of the differences, as might differences in donor populations. It seems unlikely that shipping distances play a major role in platelet activation rates but it’s possible that other confounding factors in this observational study are driving the differences between suppliers.
If you have any hypotheses for the differences between suppliers or other comments related to this post please share them in the comments section below.

References

1. Maurer-Spurej, E., Larsen, R., Labrie, A., Heaton, A. and Chipperfield, K. (2016). Microparticle content of platelet concentrates is predicted by donor microparticles and is altered by production methods and stress. Transfusion and Apheresis Science, 55(1), pp.35-43. https://sciencedirect.com/science/article/pii/s1473050216300787

2. Dumont LJ, Gulliksson H, van der Meer PF, Murphy S, Nixon JG, de Wildt-Eggen J, et al. Interruption of agitation of platelet concentrates: a multicenter in vitro study by the BEST Collaborative on the effects of shipping platelets. Transfusion. 2007;47(9):1666-73. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1537-2995.2007.01339.x

3. Tobian AA., King KE., Borge PD., Fuller AK., Uglik K., Ness PM. Platelet corrected count increments by apheresis platform. Transfusion. 2016;56(10): 2583-6. https://www.ncbi.nlm.nih.gov/pubmed/27572682

4. Macher S., Sipurzynski-Budrass S., Rosskopf K., Rohde E., Griesbacher A., Groselj-Strele A., Lanzer G., Schallmoser K. Function and activation state of platelets in vitro depend on apheresis modality. Vox Sang. 2010;99(4): 332-40. https://www.ncbi.nlm.nih.gov/pubmed/20546206