From the Guidelines
Thrombocytopenia is diagnosed through a combination of clinical evaluation, blood tests, and sometimes bone marrow examination, with the first step being a complete blood count (CBC) to confirm a low platelet count (below 100 × 10^9/L) as defined by the international consensus report 1. The diagnosis of thrombocytopenia involves a thorough clinical evaluation, including a detailed history and physical examination, as outlined in the practice guideline developed by the American Society of Hematology 1. The history should include questions about bleeding symptoms, type and severity of bleeding, duration of bleeding, and hemostasis with prior surgeries or pregnancies. The physical examination should assess the type and severity of bleeding, and exclude other causes of thrombocytopenia, such as splenomegaly, liver disease, or lymphadenopathy.
Some key points to consider in the diagnosis of thrombocytopenia include:
- A low platelet count (below 100 × 10^9/L) confirmed by a CBC 1
- Examination of a peripheral blood smear to assess platelet size and morphology and to rule out pseudothrombocytopenia 1
- Additional blood tests to determine the cause, including liver function tests, coagulation studies (PT, PTT), and tests for specific conditions like disseminated intravascular coagulation (D-dimer, fibrinogen levels) 1
- Serological tests for HIV, hepatitis, and autoimmune disorders may be warranted 1
- A thorough medication review is essential as many drugs can cause thrombocytopenia, including heparin, quinidine/quinine, and sulfonamides 1
- In cases where the cause remains unclear, a bone marrow aspiration and biopsy may be necessary to evaluate platelet production 1
The pattern of platelet decline (acute vs. chronic), presence of bleeding symptoms, and associated medical conditions all provide important diagnostic clues. Early diagnosis is crucial as severe thrombocytopenia (platelets <20,000/μL) can lead to spontaneous bleeding and requires prompt intervention. According to the international consensus report, the severity of thrombocytopenia correlates to some extent but not completely with the bleeding risk, and additional factors (e.g., age, lifestyle factors, uremia) affect the risk and should be evaluated before the appropriate management is determined 1.
From the Research
Diagnostic Approach to Thrombocytopenia
To diagnose thrombocytopenia, a comprehensive approach is necessary, considering the various potential causes of the condition. The following steps and considerations are crucial:
- A complete blood count (CBC) and peripheral smear review are essential components of the diagnostic work-up 2, 3.
- Clinical history and laboratory features must be carefully evaluated to investigate the etiology of thrombocytopenia 2.
- Specialized tests, such as bone marrow examination, may be necessary to assist with diagnosis 2.
- Platelet parameters, including mean platelet volume (MPV), platelet-large cell ratio (P-LCR), and platelet distribution width, can help differentiate between inherited macrothrombocytopenia and acquired thrombocytopenia 4.
Laboratory Evaluation
Laboratory tests play a vital role in the diagnosis of thrombocytopenia. Key aspects include:
- A CBC is the most ordered laboratory test worldwide and provides valuable information on platelet count and other blood cell parameters 3.
- Platelet parameters, such as MPV and P-LCR, can be used to identify optimal thresholds for early identification of inherited macrothrombocytopenia 4.
- The area under the curve (AUC) for MPV and P-LCR can be used to assess their ability to distinguish between inherited macrothrombocytopenia and acquired thrombocytopenia 4.
Specific Considerations
In certain cases, specific considerations must be taken into account:
- In patients with advanced liver disease, thrombocytopenia can be a common complication, and the pathophysiology is multifactorial, including splenomegaly, reduced hepatic synthesis of thrombopoietin, and increased platelet destruction or consumption 5.
- Newly licensed oral thrombopoietin mimetics/receptor agonists, such as avatrombopag and lusutrombopag, are available for targeted treatment of thrombocytopenia in patients with advanced liver disease 5.