From the Guidelines
Immune thrombocytopenia (ITP) is diagnosed primarily through a process of exclusion after finding an isolated low platelet count (typically below 100,000/μL) without other abnormalities in the complete blood count. The diagnosis begins with a thorough medical history and physical examination to rule out other causes of thrombocytopenia, such as medications, infections, or other medical conditions, as recommended by the American Society of Hematology 2019 guidelines for immune thrombocytopenia 1. A complete blood count with peripheral blood smear examination is essential to confirm isolated thrombocytopenia and examine platelet morphology.
Diagnostic Approach
The diagnostic approach in patients with suspected ITP involves a presumptive diagnosis based on history, physical examination, complete blood count, and examination of the peripheral blood smear, without suggesting other etiologies for the thrombocytopenia, as outlined in the international consensus report on the investigation and management of primary immune thrombocytopenia 1. Bone marrow examination is not routinely required but may be performed in patients over 60 years old, those with atypical features, or before starting certain treatments to exclude other bone marrow disorders.
Additional Testing
Additional testing may include coagulation studies, tests for HIV, hepatitis C, and H. pylori, and autoimmune markers if secondary ITP is suspected, as suggested by the American Society of Hematology 2011 evidence-based practice guideline for immune thrombocytopenia 1. No specific diagnostic test confirms ITP; rather, it's diagnosed when other causes of thrombocytopenia have been excluded. The absence of enlarged lymph nodes, splenomegaly, or other abnormal physical findings supports the diagnosis of primary ITP. Platelet antibody tests are not recommended for routine diagnosis due to their poor sensitivity and specificity.
Key Considerations
Key considerations in the diagnosis of ITP include the patient's age, medical history, and the presence of any atypical features, as these factors can influence the diagnostic approach and management plan, as noted in the American Society of Hematology 2019 guidelines for immune thrombocytopenia 1. By following a thorough diagnostic approach and considering these key factors, healthcare providers can accurately diagnose ITP and develop an effective management plan to improve patient outcomes.
From the Research
Diagnosis of Immune Thrombocytopenic Purpura (ITP)
The diagnosis of ITP is based on the following criteria:
- A platelet count in peripheral blood <100 × 10(9)/L is the most important criterion for the diagnosis of ITP 2
- The diagnosis of ITP is dependent on additional findings, including the exclusion of other causes of isolated thrombocytopenia using patient history, physical examination, blood count, and evaluation of the peripheral blood film 3
- The peripheral blood smear should show a small number of large platelets with normal morphology, and there should not be an increased number of schistocytes 4
Key Findings
- ITP can be classified into three types, namely, acute, subchronic, and persistent, based on disease duration 2
- The clinical treatment goals should be to resolve bleeding events and to prevent severe bleeding episodes, with a target platelet count of > 20-30 × 10⁹/L 3
- The decision to treat should be based on the bleeding severity, bleeding risk, activity level, likely side effects of treatment, and patient preferences 2, 3
Diagnostic Considerations
- The diagnosis of ITP remains one of exclusion, despite the ability to detect anti-platelet antibodies 5
- The bare minimum workup for ITP in the emergency department includes a complete blood count and a peripheral blood smear 4
- Patients with ITP may be asymptomatic, or they may have mild bleeding like petechiae, purpura, or epistaxis, or in rare cases, they may present with life-threatening bleeding 4