A patient taking warfarin presents with clinical findings showing INR: 2.5 and platelets: 30,000/μL. What laboratory tests would you request for further evaluation before an invasive procedure?

Correct answer: A. INR and platelet count

• A. CORRECT. For a warfarin patient, both INR (to assess the adequacy and safety of anticoagulation — therapeutic range is typically 2.0–3.0) AND platelet count are essential. This patient's platelet count of 30,000/μL is critically low (normal: 150,000–400,000/μL) and represents a separate bleeding risk from the anticoagulation. Both values together give a complete picture of hemostatic competence.
• B. INCORRECT. PTT (partial thromboplastin time) monitors heparin therapy, not warfarin. Bleeding time is no longer recommended as a standard pre-operative test by most guidelines. For this clinical scenario, INR and platelet count are most directly relevant.
• C. INCORRECT. PT/INR alone is insufficient when the platelet count is critically low. The platelet count represents a separate, significant bleeding risk that must also be evaluated and addressed.
• D. INCORRECT. CBC with differential provides platelet count but does not directly measure the coagulation pathway affected by warfarin. INR is needed to assess anticoagulation level and safety for the procedure.