11th January 2024

A 53-year-old hairdresser is seen in the outpatient respiratory clinic.

A 53-year-old hairdresser is seen in the outpatient respiratory clinic. Two months ago, she was diagnosed with a right-sided pleural effusion incidentally on a chest x-ray when presenting to the Emergency Department with chest pain. She remains well, and her only clinical findings on examination are reduced air entry to the right lung base with dullness to percussion. Her observations in clinic today are respiratory rate 18/min, saturations 99% breathing air, heart rate 91bpm, blood pressure 130/68mmHg and temperature 36.9 degrees Celsius. Her diagnostic aspiration showed the below. 

Investigations: 

Pleural fluid protein: 36g/L 

Pleural fluid LDH: 678 units/L

Pleural fluid pH: 7.56

Pleural fluid M, C+S: Lymphocyte predominance, negative gram staining and culture. 

Pleural fluid cytology: Negative

What is the next most appropriate investigation to request to determine the cause of her pleural effusion?

Select the SINGLE most appropriate option from the list below. Select ONE option only.