What is the initial workup and treatment for a patient with thrombocytopenia (low platelet count)?

Initial Workup and Treatment for Thrombocytopenia

The initial workup for thrombocytopenia should include a complete blood count with peripheral smear, review of previous platelet counts, coagulation studies, liver and renal function tests, and ruling out pseudothrombocytopenia by collecting blood in a tube containing heparin or sodium citrate. 1

Diagnostic Evaluation

Step 1: Confirm True Thrombocytopenia

• Rule out pseudothrombocytopenia (occurs in ~0.1% of adults)
  • Collect blood in a tube containing heparin or sodium citrate
  • Examine peripheral blood smear for platelet clumping
  • Look for EDTA-induced platelet agglutination 1

Step 2: Determine Acuity

• Review previous platelet counts to distinguish acute from chronic thrombocytopenia
• Acute thrombocytopenia may require hospitalization
• Chronic thrombocytopenia (>12 months) suggests different etiologies 1, 2

Step 3: Essential Laboratory Tests

• Complete blood count with peripheral smear
• Coagulation studies (PT, PTT)
• Liver and renal function tests
• Additional tests based on suspected etiology:
  • Infectious causes: HIV, Hepatitis C, H. pylori
  • Autoimmune workup: ANA, antiphospholipid antibodies
  • If heparin exposure: Anti-PF4 antibodies
  • If thrombotic microangiopathy suspected: D-dimer 1

Step 4: Bone Marrow Examination

• Indicated for:
  • Persistent thrombocytopenia with no response to therapy
  • Suspected bone marrow disorders
  • Unexplained thrombocytopenia in older patients 1

Treatment Approach Based on Platelet Count and Clinical Presentation

Severe Thrombocytopenia (Platelet Count <10 × 10^9/L)

• High risk of serious bleeding
• Platelet transfusion recommended for active hemorrhage
• Activity restrictions to avoid trauma-associated bleeding 1, 2

Moderate Thrombocytopenia (Platelet Count 10-50 × 10^9/L)

• Monitor for skin manifestations (petechiae, purpura, ecchymosis)
• Activity restrictions for counts <50 × 10^9/L 2

Mild Thrombocytopenia (Platelet Count >50 × 10^9/L)

• Generally asymptomatic
• May not require immediate intervention unless procedures planned 2

Treatment for Specific Etiologies

Immune Thrombocytopenia (ITP)

1. First-line therapy:

   • Short course of corticosteroids (prednisone 1-2 mg/kg/day for maximum 14 days)
   • IVIG (0.8-1 g/kg single dose) for rapid response
   • IV anti-D (50-75 μg/kg) if patient is Rh-positive and not splenectomized 1

2. Second-line therapy:

   • Thrombopoietin receptor agonists (TPO-RAs) like romiplostim or eltrombopag
     • Initial dose of romiplostim: 1 mcg/kg subcutaneously weekly
     • Adjust dose by increments of 1 mcg/kg to achieve platelet count ≥50 × 10^9/L
     • Maximum dose: 10 mcg/kg weekly 1, 3
   • Rituximab
   • Splenectomy (typically delayed at least 1 year after diagnosis) 1

Heparin-Induced Thrombocytopenia (HIT)

• Immediately discontinue all heparin products
• Switch to alternative non-heparin anticoagulants
• Do not initiate warfarin until platelet count has recovered 1, 4

Drug-Induced Thrombocytopenia

• Identify and discontinue the offending medication
• Common culprits: glycoprotein IIb/IIIa inhibitors, vancomycin, linezolid, beta-lactam antibiotics, quinine, antiepileptic drugs 5

Procedure-Related Platelet Count Thresholds

Procedure	Platelet Count Threshold
Central venous catheter insertion	>20 × 10^9/L
Lumbar puncture	>40 × 10^9/L
Epidural catheter insertion/removal	>80 × 10^9/L
Percutaneous tracheostomy	>50 × 10^9/L
Major surgery	>50 × 10^9/L
Neurosurgery or posterior segment ophthalmic surgery	>100 × 10^9/L [1]

Monitoring and Follow-up

• Daily CBC during acute phase
• Weekly CBC during dose adjustment phase of therapy
• Monthly CBC after establishing stable treatment
• Regular assessment for signs of bleeding
• For patients on TPO-RAs who discontinue treatment, monitor platelet counts weekly for at least 2 weeks 1, 3

Important Considerations and Pitfalls

• Some conditions can present with both thrombocytopenia and thrombosis (antiphospholipid syndrome, HIT, thrombotic microangiopathies) - don't assume bleeding risk only 2
• Avoid platelet transfusions in HIT or thrombotic thrombocytopenia as they may worsen thrombosis 4
• Warfarin should not be initiated in HIT until platelet count recovers and patient is on alternative anticoagulation 4
• For vaccine-induced immune thrombotic thrombocytopenia (VITT), use IVIG and non-heparin anticoagulants if thrombosis is present 1