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

From the Guidelines

The workup for thrombocytopenia should begin with a complete blood count with peripheral smear, followed by a comprehensive metabolic panel, coagulation studies, and evaluation for potential causes such as medications, infections, or autoimmune conditions, as recommended by the most recent guidelines 1. The initial evaluation should include a thorough history and physical examination, with special attention to history of viral illness, lymphocyte depleting therapy, and personal or family history of autoimmunity 1.

Initial Testing

• Complete blood count with peripheral smear to confirm the low platelet count and assess for other abnormalities
• Comprehensive metabolic panel to evaluate for underlying liver or kidney disease
• Coagulation studies (PT/INR, PTT) to assess for coagulopathy
• Evaluation for potential causes such as medications, infections, or autoimmune conditions

Specialized Testing

• HIV, hepatitis serologies, and ANA to evaluate for underlying infections or autoimmune conditions
• Blood cultures if infection is suspected
• Bone marrow aspiration and biopsy may be necessary if the cause remains unclear after initial testing, particularly to rule out malignancies or bone marrow failure syndromes
• Additional specialized testing might include testing for heparin-induced thrombocytopenia (HIT antibodies) if the patient has had heparin exposure, ADAMTS13 activity for suspected TTP, or platelet antibody testing for immune thrombocytopenia (ITP) 1.

Management

Management depends on the severity and cause of thrombocytopenia, with urgent treatment needed for counts below 10,000/μL or active bleeding, and grading of management based on platelet count, as outlined in the guidelines 1.

• For grade 1 thrombocytopenia (platelet count 75 to 100/mL), continue immune checkpoint inhibitor therapy with close clinical follow-up and laboratory evaluation
• For grade 2 thrombocytopenia (platelet count 50 to 75/mL), hold immune checkpoint inhibitor therapy and administer prednisone 1 mg/kg per day orally for 4 weeks followed by taper over 4-6 weeks to the lowest effective dose, with optional use of IVIG for rapid increase in platelet count 1.

From the Research

Thrombocytopenia Workup

The workup for thrombocytopenia involves several steps to determine the underlying cause and severity of the condition.

• The first step is to exclude pseudothrombocytopenia by collecting blood in a tube containing heparin or sodium citrate and repeating the platelet count 2.
• If thrombocytopenia is confirmed, the next step is to distinguish acute from chronic thrombocytopenia by obtaining or reviewing previous platelet counts 2.
• A complete blood count and peripheral blood smear are essential in the diagnosis of immune thrombocytopenia (ITP) 3.
• Patients with thrombocytopenia as part of a multisystem disorder usually require urgent evaluation and treatment, while those with isolated thrombocytopenia may have drug-induced thrombocytopenia, ITP, or pseudothrombocytopenia 4.

Classification and Treatment

Thrombocytopenia can be classified into different types based on the underlying cause and severity.

• ITP can be classified into three types: acute, subchronic, and persistent, based on disease duration 5.
• Treatment for thrombocytopenia depends on the underlying cause and severity, and may include platelet transfusions, corticosteroids, intravenous immunoglobulin, and other medications 2, 5, 3.
• Patients with platelet counts less than 10 × 10^3 per μL have a high risk of serious bleeding and may require hospitalization and urgent treatment 2.
• Patients with platelet counts between 20 and 50 × 10^3 per μL may have mild skin manifestations, while those with platelet counts greater than 50 × 10^3 per μL are generally asymptomatic 2.

Management and Prognosis

The management of thrombocytopenia involves treating the underlying cause and preventing bleeding complications.

• Patients with thrombocytopenia should adhere to activity restrictions to avoid trauma-associated bleeding, especially those with platelet counts less than 50 × 10^3 per μL 2.
• A low platelet count is a strong and independent predictor of an adverse outcome in critically ill patients, and may guide the use of complex or expensive treatment strategies 6.
• The goal of treatment for ITP is to achieve a platelet count associated with adequate hemostasis, rather than a normal platelet count, and the decision to treat should be based on bleeding severity, bleeding risk, and patient preferences 5.