A 45-year-old man presents with fever, weight loss, and severe abdominal pain. He also reports numbness and tingling in his feet. On examination, he has livedo reticularis on his legs and a mononeuritis multiplex. Laboratory tests reveal elevated inflammatory markers (ESR and CRP) and hepatitis B surface antigen positivity. Which of the following is the most appropriate diagnostic test to confirm polyarteritis nodosa in this patient?
