A 48-year-old male presents with dizziness, fatigue, and lower extremity edema for 3 months, and palpitations/dyspnea when climbing 3 flights of stairs for 2 weeks. Physical exam: severe anemic appearance, heart rate 120 bpm, grade III systolic murmur at apex, no hepatosplenomegaly. Lab: hemoglobin 66g/L, hematocrit 0.20 (20%). What is the FIRST outpatient test for this patient?