Accurate diagnosis has never been straightforward for aspergillosis, but modern tools are being developed rapidly and are now improving the speed and accuracy of diagnosis.
A patient presenting at the clinic will first be asked to give a history of the symptoms that they have noticed. Depending on this history a number of tests may be requested from the following list:
A blood test
X-rays or CT scan of the chest
A skin test to measure sensitivity to Aspergillus allergens
Culture and analysis of a sputum (mucus) sample
Culture of tissue fluids e.g. lung fluid (called BAL)
A bronchoscopy – where a flexible tube is passed down into the lungs while under sedation.
A sample or biopsy of a tissue mass (if present) in a lung cavity
What do the tests show?
A blood sample may be taken and sent to the laboratory to analyse whether antibodies to aspergillus are present in the blood – this test may also be called an aspergillus precipitin test. A positive result means that antibodies to the fungus have been detected. A positive test result is a useful marker for later comparisons to assess efficiency of treatment. Occasionally a false positive result may occur which is why a number of different tests are used in diagnosing aspergillosis. Sometimes markers of allergy to aspergillus are positive in the blood. A test for a particular fungal molecule sometimes found in the blood - called the galactomannan test may also be carried out on a blood sample.
In addition other tests include blood count, plasma viscosity and C-reactive protein which may indicate inflammation - such markers usually improve on treatment so a baseline level is helpful. Liver and kidney function tests are important as liver function can be abnormal on antifungal drugs. Also some aspergillosis patients may have low levels of a substance called mannose binding lectin (MBL) and display abnormal genes for this protein.
A chest X-ray allows visualisation of the inside of the lungs and may identify an abnormality such as any lung cavities - formed as a result of another underlying disease or infection, or if a fungal ball (aspergilloma) is present. more details. A more advanced cross sectional picture of the lungs may be needed in which case computer tomography (CT) may be necessary. The procedure relies on X-rays to produce a detailed image. You will need to lie still on a narrow table, which slides into the centre of the CT scanner where the X-rays rotate around you. A scan normally takes only a few minutes. more details.
A skin test where a small needle is used to scratch the surface of the skin can be used to detect whether a patient has circulating IgE antibodies specific for Aspergillus. This is a more common test if you have asthma or ABPA. A positive result indicates that the patient is sensitised to aspergillus. see immune system
A sample of sputum or other tissue fluids or tissue biopsies may be sent to the laboratory to be cultured to see if it is possible to grow aspergillus from the sample using a special culture plate, usually at the same time the sample is analysed by microscopy with specific stains to aid the identification of any aspergillus present. Another way of detecting Aspergillus is with a sensitive molecular testing method.
A bronchoscopy is a procedure where a flexible tube is passed into the lungs to view the lung and airways, during which the patient is sedated. Samples of the lung tissue or fluids can be biopsied through the bronchoscope for examination in the laboratory by culture and molecular tests, if needed. more details
Biopsies are small samples of tissue taken from infected areas (e.g. lung, sinus) that are sliced thinly, stained and examined under a microscope (examples) or are placed on nutrient media that allows any fungus present to grow - the fungus can then be identified.
The results of the above tests are then considered together and if aspergillosis is confirmed a suitable treatment regime will be started.