Pleural effusion Quiz: Ace Your Exams

A 55-year-old man with a history of COPD presents to the emergency department with fever, progressive dyspnea, and productive cough with yellow sputum over the past 3 days. His albuterol inhaler has not provided relief. Additionally, he has noticed sharp pain in his left chest while taking deep breaths. Temperature is 38.2 °C (100.8 ℉), pulse is 122/min, blood pressure is 114/78 mmHg, respiratory rate is 18/min, and SpO₂ is 87% on room air. On examination, there are decreased breath sounds in the left lung base with decreased tactile fremitus. His chest X-ray is shown below. Laboratory studies demonstrate a serum protein level of 7.2 g/dL and serum LDH of 200 U/L (upper limit of normal 280 U/L). Which of the following additional laboratory findings would be expected after thoracentesis is performed?