Manchester University NHS Foundation Trust scientists help clear up controversy over PCR test for fungal pneumonia

Pneumocystis is an unusual fungus that causes pneumonia in people with weakened immune systems. It is tricky to diagnose because it cannot be cultured in the laboratory and is easy to miss.. Sadly, this means that some patients need to take toxic sulfa medication ‘just in case’.

The NHS now uses a modern DNA-based test called polymerase chain reaction (PCR), which is much more sensitive, but in some countries (including the USA) there has been much controversy over whether this test is accurate enough to rely on.

To settle this question, a group of scientists including several from MFT have just published a new statistical analysis that combines all the available high-quality PCR data from the past 10 years (55 studies containing more than 11,000 test results).

The test was found to be around 90% accurate, with slightly better performance for samples taken from deeper inside the lungs. They give clear advice on which situations the test can be used to rule the infection in or out, and how to combine it with another fungal test (b-1-3-D-glucan) to identify false positives caused by people colonized with Pneumocystis in their lungs without developing a full infection.

The group are now reaching out to doctors and laboratory staff around the world to encourage them to implement these recommendations. While this infection is relatively rare, these results are likely to improve the lives of patients struggling with various types of immune problems such as people taking steroids for inflammatory/autoimmune conditions, or living with HIV, or recipients of organ/bone marrow transplants, or those receiving cancer treatment.

“The historical difficulties in diagnosing this infection has resulted in many cases being treated on clinical suspicion alone. Our study highlights a new direction in diagnosis but also signposts where treatment is inappropriate and unnecessary if patients do not have confirmed disease”

Dr Riina Rautemaa-Richardson

Head of Service

Mycology Reference Centre Manchester (MRCM)

You can read the paper in Clinical infectious Diseases or follow MRCM on Twitter (@MycologyRefManc)