Platelet Variability Index

A measure of platelet count fluctuations in patients with immune thrombocytopenia

Key Points

  • The platelet variability index (PVI) captures fluctuations in platelet count levels and severity of thrombocytopenia.
  • The PVI Score ranges from 0 (low likelihood of ITP) to 6 (high likelihood of ITP).
  • The PVI Scores can help distinguish ITP patients from patients with thrombocytopenia due to a non-immune cause (e.g. liver disease, splenomegaly, hereditary thrombocytopenia, etc.)

Immune thrombocytopenia (ITP) is an acquired autoimmune platelet disorder characterized by a low platelet count (thrombocytopenia), defined as a level below 100 x 10⁹/L, with no known cause. The lack of a diagnostic test for ITP and similarities with other platelet disorders makes it difficult to distinguish ITP from other causes of thrombocytopenia. Consequently, approximately 1 in 7 patients in the clinic are misdiagnosed, leading to unnecessary treatments, avoidable treatment-related toxicities and case-mix in clinical trials.

Fluctuations in platelet count levels over time occurs commonly in patients with ITP, while platelet count levels in patients with non-immune thrombocytopenia tend to stay stable over time. We developed the platelet variability index (PVI) to capture both the fluctuations in platelet count and severity of the thrombocytopenia and the PVI score, ranging from 0 (low likelihood of ITP) to 6 (high likelihood of ITP). PVI scores can help distinguish ITP patients from patients with thrombocytopenia from a non-immune cause.

REFERENCES:

Li N, et al., Arnold DM. Development and internal validation of a clinical prediction model for the diagnosis of immune thrombocytopenia. J Thromb Haemost. 2022;20(12):2988-2997. doi:10.1111/jth.15885
Li N, et al., Arnold DM. Platelet variability index: a measure of platelet count fluctuations in patients with immune thrombocytopenia. Blood Adv 2021; 5 (20): 4256–4264. doi: 10.1182/bloodadvances.2020004162