Fungal diagnostics update: new tests, clearer answers—and why no test should be used alone.
This week’s research update focuses on diagnosing aspergillosis: how clinicians distinguish Aspergillus-related disease from other lung conditions, and how newer tests may help provide clearer answers.
Diagnosing an Aspergillus-related illness is often more complicated than people expect. Symptoms can overlap with asthma, COPD, bronchiectasis, pneumonia and many other conditions. A test may detect Aspergillus without showing whether it is causing disease, and different forms of aspergillosis need different combinations of tests.
This update looks at recent research on how fungal diagnosis may become quicker and more precise. The overall message is encouraging: new molecular tests and biomarkers may add useful information. But they work best when interpreted alongside symptoms, scans, existing lung disease and other laboratory results.
Why fungal diagnosis is changing
A new review of fungal diagnostics explains why traditional culture remains useful but has limitations. Fungi can take time to grow in the laboratory and may not grow from every sample, even when infection is present.
Newer approaches include fungal antigen tests, blood biomarkers, PCR and sequencing methods, and simpler point-of-care tests. These may speed up diagnosis or detect infection when culture is negative. However, availability, cost and differences between laboratories still matter.
For patients and non-specialist clinicians, the important point is that there is unlikely to be one “perfect” Aspergillus test. Good diagnosis usually comes from putting several pieces of evidence together.
Metagenomic sequencing: a promising addition to the diagnostic toolkit
Metagenomic next-generation sequencing, usually shortened to mNGS, is a way of looking for genetic material from many different microorganisms in a single sample. Instead of choosing one organism to test for, it can search more broadly for bacteria, viruses and fungi.
A new systematic review and meta-analysis combined 12 studies of mNGS for invasive pulmonary aspergillosis. Overall, the test had a pooled sensitivity of 75% and specificity of 93%. In the included studies, it was more sensitive than galactomannan testing, fungal culture and beta-D-glucan.
These results are encouraging, especially for people at high risk of invasive infection. However, a sensitivity of 75% also means that mNGS can miss some cases. It is not a replacement for clinical assessment, scans, conventional microbiology or other fungal tests. The studies also suggest that bronchoalveolar lavage fluid—collected during a bronchoscopy—may be the most useful sample type.
Finding Aspergillus is not always the same as finding infection
One of the most difficult questions in respiratory medicine is whether Aspergillus found in a sputum or lung sample is causing infection, contributing to allergic disease, or simply present without causing harm. This is often called the difference between infection and colonisation.
A study of 178 people with suspected invasive pulmonary aspergillosis examined mNGS on fluid taken from the lungs during bronchoscopy. Higher amounts of Aspergillus genetic material were more common in people judged to have infection than in those considered colonised. In people with weakened immune systems, higher amounts were also associated with poorer outcomes.
This is useful real-world research, but it does not create a universal cut-off for every laboratory or patient group. The study was retrospective and carried out in a particular clinical setting. Its real value is in reinforcing that a result needs interpretation: the amount detected, a person’s immune system, scan findings and symptoms all matter.
Could ABPA monitoring become more precise?
Total IgE is widely used to help monitor allergic bronchopulmonary aspergillosis (ABPA), alongside symptoms, lung function and imaging where needed. A new study explored whether more specific blood tests against individual Aspergillus fumigatus proteins might provide extra information.
The researchers followed 122 people receiving ABPA treatment. A marker called recombinant Asp f4-specific IgE rose in all 15 people who experienced an ABPA exacerbation during follow-up. Total IgE rose in 12 of the 15 people.
This is promising, particularly because identifying a flare-up early can be difficult. But these tests are not ready to replace total IgE monitoring in routine care. Larger studies in different centres are needed to confirm how reliable and useful they are.
Beta-D-glucan: useful, but not an Aspergillus-specific test
Beta-D-glucan (BDG) is a blood test that detects part of the cell wall of many fungi. It can support the diagnosis of invasive fungal infection, particularly in people with immune suppression or severe illness.
A new review emphasises both its value and its limits. BDG can be raised with several fungal infections, including invasive aspergillosis, but it cannot tell clinicians which fungus is present. It is also not a reliable test for every fungal infection: for example, it may be negative in mucormycosis and cryptococcosis.
As with all tests, a result is most useful when the chance of infection was already meaningful. Testing people at very low risk can produce misleading positive results and unnecessary antifungal treatment. BDG should therefore be used alongside risk factors, scans, microbiology and other appropriate fungal biomarkers—not on its own.
What this means in practice
Fungal diagnosis is moving towards combining several sources of information more quickly: symptoms and medical history, scans, culture, antigen and antibody tests, molecular testing and, where appropriate, bronchoscopy samples.
For people living with ABPA, CPA or another Aspergillus-related condition, this research does not mean that everyone needs more tests. It does mean that better tools are gradually becoming available when diagnosis is uncertain or when a person is seriously unwell. For non-specialist clinicians, the key message is to consider Aspergillus in the right clinical setting and seek specialist microbiology or respiratory advice when the results and the clinical picture do not match neatly.
This update summarises recently published research for patients, carers and non-specialist healthcare professionals. It does not replace individual medical advice or specialist interpretation of test results.