21st February 2025

A 71-year-old man is referred to Ambulatory Care by his GP with examination findings suggestive of bilateral pleural effusions, which are confirmed by chest X-ray on arrival at the hospital.

A 71-year-old man is referred to Ambulatory Care by his GP with examination findings suggestive of bilateral pleural effusions, which are confirmed by chest X-ray on arrival at the hospital. Apart from new breathlessness over the last few weeks, he has been otherwise well. He has a past medical history of recently diagnosed hypertension for which he has been started on ramipril. He consents to a pleural aspirate to try and identify the cause of the effusion. Some of the initial results are detailed below:

Which additional test on the pleural fluid would be most helpful in identifying the underlying cause?

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