What is the workup for thrombocytopenia (low platelet count)?

From the Guidelines

The workup for thrombocytopenia begins with a thorough history and physical examination, followed by a complete blood count with peripheral smear review, as this approach helps identify the underlying cause, which is crucial for appropriate management of thrombocytopenia. Initial laboratory tests should include liver function tests, renal function tests, coagulation studies (PT, PTT), and assessment for hemolysis (reticulocyte count, LDH, haptoglobin, and direct Coombs test) 1.

Key Components of the Workup

• Bone marrow examination is indicated when peripheral causes are not evident or when there's suspicion of hematologic malignancy.
• Specific testing should be guided by clinical presentation: + HIT antibody testing for patients with recent heparin exposure + ADAMTS13 activity for suspected TTP + HIV and hepatitis testing for infection-related thrombocytopenia + Autoimmune markers like ANA for immune-mediated causes
• Drug-induced thrombocytopenia requires medication review and possible discontinuation of suspected agents.
• Platelet antibody testing may be useful in suspected immune thrombocytopenia (ITP), though this is often a diagnosis of exclusion.

Urgency of Workup

The severity of thrombocytopenia and presence of bleeding should guide the urgency of workup, with platelet counts below 20,000/μL or active bleeding requiring immediate evaluation and possible treatment, as suggested by guidelines for the management of thrombocytopenia in various clinical settings 2, 3.

Management Considerations

Prophylactic platelet transfusion should be administered to patients with thrombocytopenia resulting from impaired bone marrow function to reduce the risk of hemorrhage when the platelet count falls below a predefined threshold level, according to the American Society of Clinical Oncology clinical practice guideline update 3. For patients with alloimmune refractory thrombocytopenia, HLA-matched platelets or histocompatible platelet donors identified by cross-matching techniques may be used, as outlined in guidelines for platelet transfusion in patients with cancer 4.

Prioritization of Care

In the context of thrombocytopenia, prioritizing the identification of the underlying cause and managing the condition based on its severity and the presence of bleeding is crucial for reducing morbidity, mortality, and improving quality of life. This approach is supported by the most recent and highest quality studies available, emphasizing the importance of a systematic and patient-centered approach to the workup and management of thrombocytopenia.

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Initial Evaluation

The workup for thrombocytopenia (low platelet count) begins with excluding pseudothrombocytopenia by collecting blood in a tube containing heparin or sodium citrate and repeating the platelet count 5. If thrombocytopenia is confirmed, the next step is to distinguish acute from chronic thrombocytopenia by obtaining or reviewing previous platelet counts 5.

Laboratory Tests

Key laboratory tests in the evaluation of thrombocytopenia include:

• Complete blood count (CBC) to determine the severity of thrombocytopenia and to identify other cytopenias 6, 7
• Peripheral blood smear to examine platelet morphology and to identify schistocytes or other abnormalities 6, 8
• Screening for signs of bleeding, such as petechiae, purpura, or ecchymosis 5, 7

Classification and Management

Thrombocytopenia can be classified as:

• Mild: platelet count between 100 and 150 × 10^9/L, often asymptomatic 5, 7
• Moderate: platelet count between 50 and 100 × 10^9/L, may have mild bleeding symptoms 5, 7
• Severe: platelet count less than 50 × 10^9/L, at risk for significant bleeding 5, 7 Management of thrombocytopenia depends on the underlying cause and severity of the condition, and may include:
• Platelet transfusions for patients with active bleeding or severe thrombocytopenia 5, 6, 8
• Corticosteroids and intravenous immune globulin (IVIG) for patients with immune thrombocytopenia (ITP) 6
• Treatment of underlying conditions, such as discontinuation of offending medications or management of underlying infections 5, 7

Emergency Situations

Emergency situations that require immediate attention include:

• Active bleeding 5, 6, 9
• Platelet count less than 30 × 10^9/L 9
• Signs of disseminated intravascular coagulation (DIC) or acute renal failure 9
• Significant and/or brutal onset pancytopenia 9