Point of care tests in the diagnosis of chronic and allergic aspergillosis

Chronic and allergic forms of aspergillosis are an increasingly recognised global health problem. They are caused by the fungus Aspergillus, a very common environmental mould. We breathe in fungus particles daily, but we are usually able to clear them from the lungs. In some cases though, the fungus can establish itself in the lung and cause disease. This usually happens in people with weak immune systems, such as after chemotherapy for cancer, but can also happen on a background of chronic lung disease, like previous tuberculosis (TB) or chronic obstructive lung disease (COPD). This disease is termed chronic pulmonary aspergillosis (CPA).

One in 5 people is expected to develop CPA after successful treatment of TB: this means that CPA affects 1.2 million people globally as a consequence of TB. The number of new TB cases in Indonesia exceeds 1 million per year, making Indonesia the country with the 2nd largest number of TB cases in the world. As TB and CPA may present with the same symptoms, CPA may be mistaken and treated as TB. If CPA is not diagnosed and treated, it can result in lung destruction, weight loss, cough and blood in the sputum. Treatment exists in the form of antifungal medication. It is difficult to diagnose CPA, as diagnosis relies on specialist laboratory tests not available in most low and middle-income countries. A point-of-care (POC) blood test, performed in clinic without the need to send the sample to a laboratory would make CPA much easier and cheaper to diagnose.

We plan to use a recently developed POC test that detects Aspergillus antibody in blood in patients who present with suspected but not confirmed TB in Indonesia, and to compare with a standard serological test. The results will be made known to the physicians who can then decide on best treatment. So we can assess the importance of the result, we will follow the patients for 12 months for signs of deterioration in their symptoms and chest X-Ray. We will also compare the outcomes in patients who were treated with antifungal medication for CPA. We hope we can prove that the POC test can be used to diagnose CPA in low and middle-income settings.

In high-income settings where TB is less common, such as the UK, CPA mainly affects patients with chronic respiratory disease like COPD or bronchiectasis. The diagnosis is made by bronchoscopy and testing of bronchoalveolar lavage fluid for Aspergillus; however, the tests are neither sensitive nor specific. Turn around time, even for specialised labs, may be long and cost is high. A POC test for diagnosis of Aspergillus from pulmonary secretions would speed up diagnosis in this setting too. We plan to compare two POC tests with the conventional methods for the diagnosis of CPA in patients having bronchoscopies. As the gold-standard, we will use a new technology to analyse the entire population of fungi in the lung (called the mycobiome).

Allergic bronchopulmonary aspergillosis (ABPA) complicates 1-4% of cases of asthma globally. It results in poor control of asthma, frequent admissions to hospital and use of long-term steroids which have several side effects. Diagnosis requires either an allergy skin test or blood test. Treatment with antifungals improves symptoms and leads to reduced steroid use. There are more than 13 million asthmatics in Indonesia, and more than 300 thousand with ABPA according to estimates; the majority would be unrecognised if testing is not undertaken. Due to lack of diagnostic facilities, this is the case in most low and middle-income countries. A POC blood test detecting sensitisation to Aspergillus would be ideal for quickly screening patients with poorly controlled asthma. We will screen patients with uncontrolled asthma in Indonesia with the POC test and compare with the standard-of-care blood test. This will help provide an estimate of the rate of ABPA in Indonesia for the first time, and validate the use of this POC test for use in the screening of ABPA.

Diagnosis of chronic and allergic forms of Aspergillosis is problematic due the suboptimal performance of diagnostic tests. IgG serology is performed in specialist labs. Fungal culture is insensitive, whereas galactomannan antigen, Aspergillus PCR and Aspergillus serology lack specificity, as they can cross-react with other fungi. Molecular tests are performed in specialised laboratories, are expensive, have long turn around times due to batch testing, and are generally not available in low and middle-income countries (LMIC). POC tests offer a cheaper and more feasible alternative in LMIC and high income settings.
We will assess the performance of POC tests in 3 settings:
Aim 1. A POC Aspergillus IgG test (Aspergillus ICT IgG, LD-Bio) compared with standard-of-care serology testing in patients with presumed smear negative TB in Indonesia. We will enrol patients with presumed smear negative TB according to WHO criteria from 3 respiratory clinics in Indonesia (n=150 over 12 months). We will follow them for 12 months with serial X-Rays and symptom documentation to assess whether positive Aspergillus serology is associated with poor outcomes. We will analyse outcomes separately in patients treated with antifungals.
Aim 2. Two POC Aspergillus antigen tests (IMMY sona Galactomannan LFA and OLM AspLFD) compared with standard of care (fungal culture, Aspergillus PCR, galactomannan) in BAL fluid in patients (n=100 over 12 months) undergoing diagnostic bronchoscopies when aspergillosis is in the differential diagnosis. We will analyse the lung mycobiome as the gold standard. We will record the final diagnosis (chronic pulmonary aspergillosis vs other) and determine the sensitivity, specificity, positive predictive value and negative predictive value of the tests).
Aim 3. Two POC serological tests (Aspergillus IgG and IgE) for screening of patients with uncontrolled asthma in Indonesia (n=100) and in patients with known ABPA in the UK (n=100).

The following groups will benefit from the proposed research in the following ways:

1. Patients with chronic and allergic aspergillosis

There are multiple anticipated benefits with respect to improving health:
- A greater number of patients in Indonesia and other low and middle income countries (LMIC) with hitherto unrecognised CPA will be diagnosed and treated. There are an anticipated 80000 cases of CPA in Indonesia, most of them unrecognised, and more than 1 million globally as a sequela to TB. Antifungal treatment will improve quality of life in these patients.
- Patients misdiagnosed as presumed TB will be diagnosed as CPA, leading to reduction in use of potentially toxic anti-TB drugs and lowering the rates of antimicrobial resistance by reducing antimicrobial use.
- ABPA will be more readily diagnosed in LMICs, leading to timely antifungal treatment, reduction of steroid use and better control of asthma, avoiding admissions to hospitals and unnecessary antimicrobial use, again limiting antimicrobial resistance. There are more than 13 million asthmatics in Indonesia and the results are applicable to most LMICs.
- Better understanding of Aspergillus diagnostic tests in respiratory secretions in the setting of chronic lung disease will lead to diagnosing or ruling out aspergillosis with more confidence in patients who present with usually present with a very challenging differential diagnosis on a background of often severe lung disease. Differential diagnosis in these patients includes lung cancer or mycobacterial infection, therefore accurate and timely diagnosis will enhance patient experience and prevent unnecessary treatments.

2. Low and middle income countries' health systems

- Adoption of point of care (POC) tests will obviate the need for more expensive tests and the need for access to a specialised laboratory.
- LMICs can divert funds to screening and diagnosis of chronic and allergic aspergillosis. This will be achieved by saving on unnecessary antimicrobial and anti-TB treatment and on the cost of frequent admissions and doctor visits.

3. Researchers in the field of Aspergillosis

-We plan to make our results available for researchers following publication. The proposed research will provide novel data on the dynamics of the mycobiome in chronic lung disease, a topic that has not been investigated in detail previously. The comparison of the mycobiome with our current diagnostic tests in Aspergillosis will provide a gold standard for the evaluation of these tests that has not been used before.

4. Industry

-Proof of the usefulness of POC tests will lead to an increased interest by industry to develop new tests for other fungal infections or other infectious diseases.