Platelet Variability Index

A measure of platelet count fluctuations in patients with immune thrombocytopenia

Key Points

  • The PVI score can help distinguish between ITP and nonimmune thrombocytopenia.
  • Patients with thrombocytopenia and a high PVI score had a high likelihood of having the diagnosis of ITP.

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:

Arnold DM, Nazy I, Clare R, Jaffer AM, Aubie B, Li N, Kelton JG. Blood Adv. 2017 Nov 28;1(25):2414-2420.
Li N, Heddle NM, Nazy I, Kelton JG, Arnold DM. Platelet variability index: a measure of platelet count fluctuations in patients with immune thrombocytopenia. Blood Adv. 2021 Oct 26;5(20):4256-4264.