Review Question - QID 217661

A 53-year-old African-American woman presents to her primary care doctor with increasing difficulty climbing the stairs. She noticed the weakness approximately 3 months ago. It has gotten progressively worse since that time. She has also noticed increasing difficulty combing her hair, standing from a seated position, and experiences muscle aches. Her medical history is significant for hypertension treated with lifestyle modification and gastroesophageal reflux disease (GERD). Her temperature is 98.6°F (37.0°C), blood pressure is 130/65 mmHg, pulse is 80/min, and respirations are 16/min. She has 3/5 strength to shoulder abduction and hip flexion bilaterally. Her strength is 5/5 to wrist extension and ankle plantar flexion. No skin rashes are noted. Which of the following is the most accurate test to confirm this patient’s diagnosis?