News from the 63rd ASH Annual Meeting and Exposition
This year’s 63rd ASH Annual Meeting and Exposition was again virtual due to the global pandemic. Held December 11-14, 2021, the meeting attracted thousands of clinicians, scientists, trainees, and pharmaceutical company personnel worldwide to share ground-breaking research in the field of hematology. In this issue of the e-news, we report on research accepted at ASH by PDSA’s research staff and medical advisors showcasing the impact of COVID-19 in those with pre-existing and de novo ITP, in addition to the state of the gut microbiome at the time of diagnosis in pediatric ITP. Watch for additional ASH reports in the 2021 winter issue of The Platelet News, the PDSA quarterly newsletter.
Do Splenectomized Immune Thrombocytopenia (ITP) Patients Have Increased Risks for Platelet Decreases Following COVID-19 Vaccination?
Decreases in platelet counts following vaccine receipt have been reported among adults with pre-existing ITP. For many ITP patients, the possibility of a further reduction in platelet count can lead to vaccine hesitancy. In this study, differences in the development of thrombocytopenia between not-splenectomized (NS) and (Spl) splenectomized adult ITP patients were compared to explore if Spl ITP patients have a greater risk for platelet count decreases following COVID-19 vaccination. Data was collected using the ITP COVID-19 web-based survey that is part of the Platelet Disorder Support Association’s ITP Natural History Study Patient Registry. As of June 2021, 241 adults with ITP had received at least one vaccine dose, a post vaccine PC, and had disclosed their splenectomy status. The majority of participants included the study received an mRNA vaccine (such as Pfizer or Moderna).
Platelet count decreases were reported following both doses of a COVID-19 vaccine regardless of splenectomy status. While platelet count drops seemed to occur at a greater frequency following receipt of the first vaccine dose than after the second dose, this difference was not found to be significant. Having a splenectomy was not associated with an increased risk to experience a platelet count drop, however it was associated with the risk for a larger platelet count drop (>50,000/µL) if there was a drop in count happened at all. Comparison between Spl and NS participants with the same PC result (increase, decrease, or no change) following both vaccine doses did not reveal a statistically significant difference, meaning it was not possible to predict how the platelet count would react to the second vaccine dose based on the response to the first vaccine dose in either group.
Overall, it was concluded that COVID-19 vaccines are relatively safe for ITP patients regardless of splenectomy status. Being fully vaccinated (receiving both doses) should not be avoided if a platelet count drop was experienced following the first dose. Platelet count responses following the first dose of a COVID-19 vaccine is not a reliable maker to predict response to the second dose of the vaccine.
Comments from PDSA’s Medical Advisors:
Data on the effects of COVID immunization continue to be accumulated. Several studies were presented at ASH and a number have already been published. One of the ones presented at ASH from Belgium actually found that splenectomized patients had their platelet counts INCREASE instead of decreasing after vaccination. The chance that the platelets will drop enough and create enough bleeding and be difficult to treat is really small. The bottom line is that all of the ITP experts emphasize that receiving a vaccine is much better than not receiving it.
In this study, funded by PDSA through a Barbara and Peter T. Pruitt Jr. ITP Research Award, the impact of the gut microbiome (richness and diversity of micro-organisms such as bacteria in the intestines) on the development of ITP in children was explored. Gut ‘richness’ refers to the total number of bacterial specifics in the gut microbiome, whereas gut ‘diversity or evenness’ refers to the amount of each individuals’ bacteria from each of the species present in the gut microbiome. Previous non-ITP related investigations suggested an association between gut microbiome imbalances to various autoimmune conditions.
Stool samples were collected from 32 children a diagnosis ITP between 0-18 years at the Children’s Hospital of Philadelphia. Among these 32 participants, 17 were newly diagnosed, 7 had persistent ITP, and 8 were newly diagnosed but also had severe acquired aplastic anemia. Age-matched health control samples were also obtained. In order to determine the composition of the gut microbiome and compare it to healthy controls, shotgun sequencing (genetic testing) was used. Specialized technology was utilized to determine the diversity of microbes found in each participant.
Results revealed that newly diagnosed children with ITP (who did not have aplastic anemia) had less diversity and richness in their gut microbiome compared to healthy controls. Imbalances in the gut microbiome were not observed in the children with persistent ITP, including those who also had acquired aplastic anemia, suggesting that these gut abnormalities are only seen in newly diagnosed primary ITP and self-correct within three months of diagnosis. These findings may be due to either the development of ITP or is the cause of the ITP. Results also revealed an imbalance of certain types of bacteria (Alistripes species and Escherichia coli) in children with newly diagnosed ITP. Further understanding of the gut microbiome’s role in the pathophysiology of ITP may lead to further advances in treatment and prevention.
Comments from PDSA’s Medical Advisors:
Studies in many different diseases have explored the role of the bacteria in the intestine. Normally there are bacteria in the colon not in the small intestine. Separately, there are more nerves in the GI tract than in the brain and they function differently so that they exert a mysterious effect on many things. There were two studies at ASH that explored the role of the microbiome meaning the population of bacteria in the intestine. It is now possible with DNA sequencing panels to know which bacteria are there. Studies to date are still preliminary but demonstrate that the types of the bacteria in the gut are different in children with ITP than in children without ITP. Overall, there is still a chicken and the egg phenomenon. Would changing the microbiome improve the ITP? We don’t know. Does the ITP alter the microbiome or does the altered microbiome precede and induce the ITP? Further studies will better define this.