A 30-year-old woman with a known history of systemic lupus erythematosus (SLE) presents with new-onset shortness of breath, pleuritic chest pain, and a productive cough. Physical exam reveals dullness to percussion and decreased breath sounds at the left lung base. Chest X-ray shows a left-sided pleural effusion. Which of the following is the MOST appropriate initial diagnostic test for her pleural effusion?
✓ Correct Answer: Option A
In a patient with SLE and a new pleural effusion, thoracentesis with pleural fluid analysis is crucial. It helps differentiate between infection, malignancy, and lupus-related serositis (exudative effusion), guiding subsequent management.