What are the next steps for a patient with a history of deep vein thrombosis (DVT) in the lower extremity, who was switched from Eliquis (apixaban) to Warfarin, and also has a history of iron deficiency anemia, with current platelet count of 136,000/μL and hemoglobin of 13 g/dL?

Management of Mild Thrombocytopenia in a Patient on Warfarin for DVT

Continue warfarin therapy with close monitoring of platelet counts and INR, as a platelet count of 136,000/μL is above the threshold requiring dose modification or discontinuation, and the hemoglobin of 13 g/dL indicates no active bleeding. 1, 2

Immediate Assessment Steps

• Check INR immediately to ensure therapeutic range of 2.0-3.0, as warfarin requires regular monitoring regardless of platelet status 1, 2
• Obtain a complete blood count with differential to confirm the platelet count and evaluate for other cytopenias 3
• Review medication list for drugs that may interact with warfarin metabolism or contribute to thrombocytopenia 1
• Assess for signs of bleeding including petechiae, ecchymoses, mucosal bleeding, or occult blood loss, though current hemoglobin of 13 g/dL suggests no significant bleeding 1

Platelet Count Interpretation and Management

• Platelet count of 136,000/μL is mildly decreased but does not require anticoagulation modification, as clinically significant bleeding risk typically increases when platelets fall below 50,000/μL 3
• Continue current warfarin dose if INR is therapeutic (2.0-3.0), as this platelet level does not contraindicate anticoagulation for DVT 1, 2
• Repeat platelet count in 1-2 weeks to establish trend and rule out progressive thrombocytopenia 3

Differential Diagnosis for Thrombocytopenia

• Consider heparin-induced thrombocytopenia (HIT) if the patient received heparin bridging when transitioning from Eliquis to warfarin, though fondaparinux has insignificantly low HIT risk and does not require platelet monitoring 1
• Evaluate for pseudothrombocytopenia by reviewing the blood smear, as EDTA-dependent platelet clumping can cause falsely low automated counts 3
• Assess for drug-induced thrombocytopenia from warfarin itself (rare) or other medications 1
• Screen for underlying conditions including bone marrow disorders, autoimmune processes, or occult malignancy if thrombocytopenia persists or worsens 3

Warfarin Management Considerations

• Maintain INR in therapeutic range of 2.0-3.0 with testing frequency based on stability: every 1-2 weeks if recently initiated or unstable, extending up to 4 weeks for consistently stable patients 1, 2
• Avoid NSAIDs and antiplatelet agents unless specifically indicated (e.g., mechanical heart valves, acute coronary syndrome), as these increase bleeding risk particularly with concurrent thrombocytopenia 1, 3
• Continue warfarin for minimum 3 months for provoked DVT, or 6-12 months for unprovoked DVT, with reassessment at completion 1, 2

Thresholds for Anticoagulation Modification

• Consider dose reduction or temporary hold if platelets fall below 25,000-50,000/μL, balancing thrombosis risk against bleeding risk 3
• Avoid NSAIDs for pain control if platelets drop below 20,000-50,000/μL or if severe platelet dysfunction is present 3
• Discontinue anticoagulation only if platelets fall below 20,000/μL or if major bleeding occurs 3

Iron Deficiency Anemia Follow-Up

• Current hemoglobin of 13 g/dL indicates adequate response to prior IV iron therapy 3
• Monitor for recurrent anemia that could suggest occult bleeding from anticoagulation, particularly gastrointestinal sources 1
• Recheck iron studies (ferritin, transferrin saturation) if hemoglobin trends downward on subsequent monitoring 3

Critical Pitfalls to Avoid

• Do not discontinue warfarin based solely on mild thrombocytopenia (136,000/μL), as this increases risk of recurrent DVT without significantly reducing bleeding risk 1
• Do not switch back to Eliquis without understanding why the initial switch occurred, as there may have been a compelling reason (e.g., renal impairment, drug interactions, cost) 1, 4
• Do not overlook the possibility of HIT if heparin was used for bridging, as this requires immediate cessation of all heparin products and alternative anticoagulation 1
• Do not assume thrombocytopenia is warfarin-related without excluding other causes, including malignancy, which should be considered in breakthrough VTE on adequate anticoagulation 5