What labs should be ordered for a patient on Plavix (clopidogrel) who experiences a fall?

Laboratory Tests for Patients on Plavix (Clopidogrel) After a Fall

For patients on clopidogrel who experience a fall, obtain a platelet count, platelet function test if available, and coagulation tests (PT/INR and aPTT) to assess bleeding risk and guide management.

Initial Assessment After a Fall

• Obtain a complete blood count (CBC) with platelet count to assess for thrombocytopenia, which may increase bleeding risk in patients on clopidogrel 1
• If available, obtain a test of platelet function in patients with suspected or drug-induced (clopidogrel) platelet dysfunction 1
• Perform coagulation tests including prothrombin time (PT) or international normalized ratio (INR) and activated partial thromboplastin time (aPTT) to assess coagulation status 1
• Conduct a visual assessment for evidence of excessive microvascular bleeding or bruising 1

Additional Recommended Tests

• Perform head imaging (CT or MRI) to assess for intracranial hemorrhage, especially if there was head impact during the fall or any neurological symptoms 1
• Consider hemoglobin/hematocrit measurements to establish a baseline and monitor for occult bleeding 1
• If excessive bleeding is observed or suspected, assess fibrinogen levels before administration of cryoprecipitate 1

Special Considerations for Clopidogrel Patients

• Remember that clopidogrel is a prodrug requiring hepatic cytochrome P450 (CYP) metabolic activation to produce its active antiplatelet metabolite 1, 2
• Genetic variations in CYP2C19 can affect clopidogrel metabolism and efficacy, though routine genetic testing is not recommended for all patients 1
• Consider that concomitant medications, particularly some statins, may interact with clopidogrel metabolism 3

Management Considerations Based on Test Results

• If platelet function is significantly impaired and active bleeding is present, consider temporary discontinuation of clopidogrel, weighing thrombotic versus bleeding risks 1
• For patients with excessive bleeding, consider topical hemostatics such as fibrin glue or thrombin gel 1
• In cases of severe bleeding, platelet transfusion may be considered, though effectiveness may be limited while active clopidogrel metabolite is present 1

Monitoring After Initial Assessment

• Perform serial hemoglobin/hematocrit measurements to monitor for occult bleeding 1
• Continue to visually assess for signs of bleeding, including at the fall site and other potential injury locations 1
• Monitor vital signs for evidence of hemodynamic instability that might suggest occult bleeding 1

Common Pitfalls to Avoid

• Do not assume normal coagulation status based solely on platelet count; platelet function may be significantly impaired despite normal counts in patients on clopidogrel 1
• Remember that bleeding risk is increased when clopidogrel is combined with other antithrombotic agents, such as in patients with atrial fibrillation who may also be on anticoagulants 1
• Be aware that standard coagulation tests (PT/INR, aPTT) may not fully reflect the antiplatelet effect of clopidogrel 4