Introduction

Harrison's pod glass is brought to you by McGraw-Hill's Access Medicine, the online medical resource that delivers the latest trusted content from the best minds in medicine. We're thrilled to welcome the newest Harrison editor, Dr. Carol Langford, to discuss today's patient. He's a 46-year-old man who presented to the hospital acutely with hemoptasis, diffuse nodular pulmonary infiltrates, and glomerular nephritis. Treatment was initiated with high-dose glucocorticoids and daily cyclophosphamide with an excellent clinical response. Which of the following blood tests would you check before starting azathiopin?