Knowledge Check

Which of the following statement(s) is/are correct:

ITP stands for idiopathic thrombocytopenic purpura
No, it now stands for immune thrombocytopenia.
A diagnosis of ITP requires that the platelet count be < 100K
The term “secondary ITP” has been proposed to broadly include all forms of immune-mediated thrombocytopenias except primary ITP
Secondary forms include thrombocytopenias that are due to an underlying disease or to drug exposure. However, heparin-induced thrombocytopenia maintains its designation and acronym (HIT) because of its unique features.

20019 Standardization of terminology, definitions and outcome criteria in immune thrombocytopenic purpura of adults and children: report from an international working group:

Blood. 2009;113:2386-93.

Why we use the threshold platelet count of < 100 x 109/L to define ITP:

Stasi et al. Long-term outcome of otherwise healthy individuals with incidentally discovered borderline thrombocytopenia. PLoS Med. 2006 Mar;3(3):e24.

  • Prospective study of 260 apparently healthy individuals with incidentally discovered platelet counts between 100 x 109/L and 150 x 109/L were monitored for 6 mo to determine whether their condition persisted.
  • The monitoring period was completed in 217 cases, of whom 191 (88%) maintained stable platelet counts; these 191 individuals were included in a long-term follow-up study to gain knowledge of their natural history.
  • The 10-y probability of developing idiopathic thrombocytopenic purpura (ITP), as defined by platelet counts persistently< 100 x 109/L, was 6.9% (95% confidence interval [CI]: 4.0%–12.0%).
  • The 10-y probability of developing autoimmune disorders other than ITP was 12.0% (95% CI: 6.9%–20.8%).

Bottom line: patients with platelet counts 100-150 x 109/L rarely develop more severe thrombocytopenia when followed longitudinally. Therefore, they are not labeled with the diagnosis of immune thrombocytopenia (ITP).

Sort the time frame of ITP diagnosis at top with the definition of disease phase at bottom

Diagnosed 13 months ago
Diagnosed 2 months ago
Diagnosed 5 years ago
Diagnosed 4 days ago
Diagnosed today
Diagnosed 4 months ago
Newly diagnosed ITP
Persistent ITP
Chronic ITP

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