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?
Blood tests: Antibodies against Aspergillus proteins can be measured in a patient’s blood and this indicates if the patient may have an Aspergillus infection – this is done using an enzyme-linked immunosorbent assay (ELISA), such as the ImmunoCAP® Specific IgE Blood Test.. A positive result means that antibodies to the fungus have been detected. A positive test result is also 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.
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. A more advanced cross sectional picture of the lungs may be needed, in which case computer tomography (CT) might 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.
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, other tissue fluids or tissue biopsies may be sent to the laboratory to be cultured, in order to see if it is possible to grow Aspergillus from the sample. Scientists use a special culture plate to grow moulds, and if any does grow they often use a microscope to confirm the type of mould. 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 – the patient is sedated during the procedure. 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. See more.
Biopsies are small samples of tissue taken from infected areas (e.g. lung, sinus) that are either sliced thinly, stained and examined under a microscope, 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.
Symptoms can be widely different depending on the type of aspergillosis that a patient may have. For instance one patient with an aspergilloma may have few symptoms or just a cough, another may cough up large quantities of blood (haemoptysis) and require urgent medical attention The following is a general list of some of the symptoms which aspergillosis patients can experience – but there is a large variation between patients.
- weight loss
- coughing blood (haemoptysis)
A patient with some of these symptoms may not have aspergillosis – in fact it is unlikely, unless the person has a poor immune system (eg. following cancer therapy, organ transplantation). If a person has not responded to several doses of antibiotics and has a weakened immune system then tests for aspergillosis should be considered.