Can pleural fluid cell differentiation accurately diagnose the cause of fluid around the lung?

Pleural effusion – a build-up of fluid around the lungs – can be caused by lung cancer, heart failure or an infection, among many other things.

Pleural fluid cell differentiation is one of the tests recommended for patients who come to hospital with fluid around their lungs, to find out the cause. This test is time-consuming and there is not much evidence that it works.

Project aims

The aim of this project was to find out whether pleural fluid cell differentiation can accurately diagnose the cause of fluid around the lung.

What we did

We studied 997 patients attending a specialist lung clinic with an undiagnosed pleural effusion in one lung, between December 2008 and December 2016. We compared the results of pleural fluid cell differentiation with a confirmed diagnosis by two respiratory consultants a year later.

We found that pleural fluid cell differentiation could not be used to give a definitive diagnosis, or to rule out any specific cause.

Based on our results, we recommend that healthcare professionals do not rely on pleural fluid cell differentiation to diagnose the cause of a fluid around the lung. We also recommend further research to find out whether the test should be used at all.

What we hope to achieve

We hope our findings will lead to updated clinical guidelines on using pleural fluid cell differentiation to diagnose the cause of pleural effusion.