What are the key diagnostic criteria for immune thrombocytopenia (ITP) in adults?

Key diagnostic criteria for immune thrombocytopenia (ITP) in adults involve a diagnosis of exclusion characterized primarily by isolated thrombocytopenia (platelet count typically below 100 × 10⁹/L) without other causes of thrombocytopenia or underlying disorders.

Diagnosis requires a thorough clinical assessment and laboratory evaluation to exclude secondary causes such as infections, malignancies, drug-induced thrombocytopenia, and bone marrow disorders ¹.

ITP is suspected when there is persistent, unexplained thrombocytopenia on at least two occasions 4–6 weeks apart, with no evidence of other hematological abnormalities such as anemia or neutropenia ¹.

Bone marrow examination is not routinely required but may be considered in atypical cases or when other diagnoses are suspected ¹.

Clinical features supporting ITP include mucocutaneous bleeding manifestations and absence of splenomegaly or lymphadenopathy, which help differentiate it from other causes of thrombocytopenia ¹.

Recent hematology guidelines emphasize that ITP diagnosis is clinical and by exclusion, supported by isolated thrombocytopenia and absence of other causes, with no definitive diagnostic test available (Lambert and Gernsheimer, 2017; Neunert et al., 2019; Neunert et al., 2024).

Laboratory tests typically show isolated low platelet count with normal red and white blood cell counts and normal coagulation studies. Antiplatelet antibody testing is not routinely recommended due to low sensitivity and specificity (Neunert et al., 2019).

In summary, the key diagnostic criteria for adult ITP are:

• Isolated thrombocytopenia (platelet count <100 × 10⁹/L) persisting for at least 4–6 weeks ¹
• Exclusion of other causes of thrombocytopenia by clinical history, examination, and appropriate investigations ¹
• Absence of other hematological abnormalities or systemic disease ¹
• Supportive clinical features such as mucocutaneous bleeding without splenomegaly ¹
• Diagnosis primarily clinical and by exclusion, with no definitive confirmatory test (Lambert and Gernsheimer, 2017; Neunert et al., 2019; Neunert et al., 2024)