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

From the Guidelines

A low platelet count (thrombocytopenia) workup should begin with a complete blood count to confirm the finding, followed by a peripheral blood smear to assess platelet morphology and rule out pseudothrombocytopenia, as recommended by recent guidelines 1. The initial evaluation should include a thorough medical history focusing on medication use, recent infections, alcohol consumption, family history, and symptoms of bleeding.

• Physical examination should look for signs of bleeding, lymphadenopathy, splenomegaly, or evidence of underlying conditions.
• Laboratory tests should include liver function tests, renal function tests, coagulation studies (PT, PTT), and tests for specific conditions like HIV, hepatitis C, and autoimmune disorders (ANA, anti-phospholipid antibodies). If immune thrombocytopenia (ITP) is suspected, testing for H. pylori and bone marrow examination may be warranted, especially in patients over 60 or with atypical features.
• Treatment depends on the cause but may include stopping offending medications, treating underlying infections, or specific therapies like corticosteroids (prednisone 1-2 mg/kg/day for 2-4 weeks) for ITP, intravenous immunoglobulin (1 g/kg for 1-2 days) for severe cases, or thrombopoietin receptor agonists like eltrombopag or romiplostim for refractory cases. Platelet transfusions are generally reserved for active bleeding or counts below 10,000/μL, as supported by the AABB clinical practice guideline 1. This systematic approach helps identify the underlying cause of thrombocytopenia, which is essential for appropriate management and preventing complications like excessive bleeding.
• For patients with therapy-induced hypoproliferative thrombocytopenia, prophylactic platelet transfusions are recommended for a morning platelet count of 10 × 10^9 cells/L or less, as stated in the AABB guideline 1.
• The management of thrombocytopenia in patients treated with immune checkpoint inhibitor therapy should follow the American Society of Clinical Oncology clinical practice guideline, which provides recommendations for grading management based on platelet count 1.

From the Research

Low Platelet Count Work Up

The work up for a low platelet count, also known as thrombocytopenia, involves a systematic evaluation to identify the underlying cause.

• The approach to thrombocytopenia is different between outpatients and those presenting in the emergency department or intensive care unit, with the latter requiring immediate intervention 2.
• A complete blood count and peripheral smear review are essential components of the diagnostic work-up, and physicians should be knowledgeable about appropriate selection and interpretation of more specialized tests, including bone marrow examination, to assist with diagnosis 3.
• The diagnostic work-up should consider various etiologies, including decreased bone marrow platelet production, increased peripheral platelet destruction, increased splenic sequestration, and dilution 3.

Etiologies of Thrombocytopenia

Thrombocytopenia can be caused by various conditions, including:

• Immune thrombocytopenic purpura (ITP), an autoimmune condition characterized by a platelet count of less than 100 x 10^9/L 4.
• Infections such as HIV and hepatitis C virus 2.
• Thrombotic microangiopathies, a life-threatening disorder 2.
• Congenital thrombocytopenias, which are better-characterized conditions 3.

Treatment of Thrombocytopenia

The treatment of thrombocytopenia depends on the underlying cause and severity of the condition.

• For primary idiopathic ITP, corticosteroids are the standard first-line treatment, with the addition of intravenous immune globulin (IVIG) or Rho(D) immune globulin for steroid-resistant cases 4.
• However, extended and recurrent use of corticosteroids is associated with substantial toxicity, and clinical practice guidelines recommend limiting corticosteroid treatment to no more than 6 weeks in adults with ITP receiving initial therapy 5.
• Other treatment options, such as thrombopoietin receptor agonists, rituximab, and splenectomy, may be considered for patients who require subsequent therapy or have refractory disease 4, 5.