Herpes zoster infection (shingles) Quiz: Ace Your Exams

A 71-year-old man presents to his primary care physician for evaluation of a painful red rash for the past three days. He reports burning over the skin as well as generalized malaise prior to the onset of the rash. He is otherwise healthy and does not take any medications daily. He has a history of chickenpox in childhood. Temperature is 36°C (96.8°F), blood pressure is 145/70 mmHg, pulse is 89/min, respiratory rate is 14/min, and oxygen saturation is 100% on room air. The patient’s rash is shown in the image below. Which of the following is the best next step for diagnosing his condition?
 
^{Reproduced from: wikipedia}