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No Change in Platelet Count Threshold of Patients With ITP Treated With Aspirin

November 14, 2023

Mid-November 2023

Khylia Marshall

Khylia Marshall is a freelance journalist based in Tucson, Arizona.

Patients with immune thrombocytopenia (ITP) and a platelet count of less than 20 × 109/L who were treated with aspirin experienced bleeding at similar rates as patients with ITP who were not exposed to aspirin, according to study results published in Blood.1

The median age of patients diagnosed with ITP is 60 years. This subpopulation is susceptible to thrombosis, against which ITP does not protect; therefore, a significant proportion of these patients are exposed to antiplatelet drugs. As a result, managing the potential for bleeding poses a challenge in clinical practice.

For patients treated with antiplatelet agents, there is no clear understanding of the threshold platelet count associated with significant bleeding, and recommendations to date have been based on expert opinion only. Guillaume Moulis, MD, PhD, of Toulouse University Hospital in France, and colleagues conducted a study to delineate the bleeding risk of patients with ITP treated with antiplatelet agents, which was identified as a priority need in the 2019 American Society of Hematology guidelines for ITP.2

Researchers studied 1,171 adult patients (≥18 years) who were newly diagnosed with ITP listed in the CARMEN-France registry up to November 2021. Their cross-sectional study examined the relationship between platelet count and bleeding manifestations at diagnosis before any ITP treatment. Researchers placed patients in subgroups based on antiplatelet agent exposure and evaluated for correlations between bleeding risk and platelet count.

Of the 143 patients (12.2%) who were exposed to an antiplatelet drug at the time of diagnosis, 108 were given aspirin alone, 20 were given clopidogrel alone, and 15 were given a combination of antiplatelet agents. The subgroup exposed to aspirin alone had a median platelet count of 15 × 109/L, and 61.1% (n=66) of them experienced bleeding.

When categorized by platelet count, researchers observed an increase in bleeding as platelet counts decreased (22.2% [≥20 × 109/L], 66.7% [10-19 × 109/L], and 97.6% [<10 × 109/L]). This pattern was observed independently of site or severity of bleeding.

“The pattern of bleeding by platelet count categories in patients treated with aspirin was similar to the pattern observed in other patients with ITP,” researchers said. They noted that patients who were not exposed to antiplatelet or anticoagulant drugs experienced a bleeding frequency greater than 50% when platelet counts were less than 20 × 109/L.

Additionally, six serious bleeding events occurred in patients who were exposed to antiplatelet drugs (four in the aspirin-only group and one in each of the clopidogrel and dual antiplatelet groups), and they all occurred in patients with platelet counts lower than 10 × 109/L, thus underscoring the “risk of severe bleeding in the case of very low platelet count like in other adults with ITP not exposed to antiplatelet agents,” said Dr. Moulis.

Finally, researchers identified that the threshold of a platelet count of less than 20 × 109/L had high sensitivity (83.3%) and specificity (81%). Moreover, an area under the curve of 88.3% (95% CI 81.9-94.6) indicated “that bleeding is not so frequent in patients with ITP treated with aspirin, and the same threshold of platelet count to prevent bleeding​(> 20 × 109/L) should be considered for these patients as for other adults with ITP,” Dr. Moulis said.

High platelet turnover may explain why aspirin was not associated with bleeding, which raises concerns about “sufficient cardiovascular protection by aspirin in patients [with ITP] with a low risk of bleeding and a high cardiovascular risk,” researchers said. However, Dr. Moulis emphasized that “this is speculation only.”

A limitation to the study was the low number of patients in the clopidogrel alone and dual antiplatelet groups, which hindered the ability to determine a correlation between platelet count and bleeding in these groups. Researchers proposed a future combination of registries to make this determination, but Dr. Moulis cautioned physicians to “be careful” because they observed one intracranial bleed in each respective group.

Researchers say further “cohort studies with longitudinal analysis are now needed to assess whether maintaining a platelet count greater than 20 × 109/L is [adequate] in patients with ITP and treated with aspirin alone.”

Any conflict of interest declared by the authors can be found in the original article.

References

  1. Ollier N, Piel-Julian ML, Mahévas M, et al. Platelet count threshold for hemorrhage in patients with immune thrombocytopenia treated with antiplatelet agents. Blood. 2023;142(12):1099-1101.
  2. Neunert C, Terrell DR, Arnold DM, et al. American Society of Hematology 2019 guidelines for immune thrombocytopenia. Blood Adv. 2019;3(23):3829-3866.

 

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