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 NICE CKS.
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 NICE CKS.
Bone marrow examination is not routinely required but may be considered in atypical cases or when other diagnoses are suspected NICE CKS.
Clinical features supporting ITP include mucocutaneous bleeding manifestations and absence of splenomegaly or lymphadenopathy, which help differentiate it from other causes of thrombocytopenia NICE CKS.
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 & Gernsheimer 2017Neunert et al. 2019Neunert 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 NICE CKS
- Exclusion of other causes of thrombocytopenia by clinical history, examination, and appropriate investigations NICE CKS
- Absence of other hematological abnormalities or systemic disease NICE CKS
- Supportive clinical features such as mucocutaneous bleeding without splenomegaly NICE CKS
- Diagnosis primarily clinical and by exclusion, with no definitive confirmatory test Lambert & Gernsheimer 2017Neunert et al. 2019Neunert et al. 2024
Key References
- CKS - Platelets - abnormal counts and cancer
- NG121 - Intrapartum care for women with existing medical conditions or obstetric complications and their babies
- CKS - Bruising
- NG24 - Blood transfusion
- (Lambert and Gernsheimer, 2017): Clinical updates in adult immune thrombocytopenia.
- (Neunert et al., 2019): American Society of Hematology 2019 guidelines for immune thrombocytopenia.
- (Neunert et al., 2024): The 2022 review of the 2019 American Society of Hematology guidelines on immune thrombocytopenia.