Research significance summary for specialists: Chronic pulmonary aspergillosis during tuberculosis treatment: emerging evidence, diagnostic pitfalls and implications for TB pathways

Why this matters

CPA remains substantially under-recognised in people with current or previous pulmonary tuberculosis. The clinical overlap is considerable: cough, haemoptysis, weight loss, fatigue, cavitation and progressive radiological change can be attributed to TB relapse, treatment failure, non-tuberculous mycobacterial infection, bacterial bronchiectasis, malignancy or post-TB lung disease.

For TB programmes and respiratory services, the practical question is no longer simply whether CPA occurs after TB. The question is whether there should be defined triggers for CPA assessment during TB treatment, particularly when symptoms persist despite microbiologically effective therapy.

The traditional model: CPA after tuberculosis

The conventional model is well established:

• Pulmonary tuberculosis causes cavitation, fibrosis, bronchiectasis and pleural distortion.
• Residual cavities may persist after microbiological cure.
• Aspergillus conidia can colonise these abnormal airspaces.
• In some patients, colonisation progresses to simple aspergilloma, chronic cavitary pulmonary aspergillosis or chronic fibrosing pulmonary aspergillosis.

This model is supported by older post-TB aspergilloma studies and by modern CPA burden estimates. Bongomin’s review of post-tuberculosis CPA highlights residual pulmonary cavities as a major risk substrate and summarises classic British data in which Aspergillus precipitins and aspergillomas increased over time after treated pulmonary TB.

The newer question: can CPA be present or emerge during TB treatment?

Several recent prospective studies suggest that CPA may be detected during the active TB treatment pathway, not only years after treatment completion.

1. Jha et al. 2024: serial CPA assessment during treatment of newly diagnosed PTB

Jha and colleagues conducted a prospective study of newly detected pulmonary tuberculosis cases and assessed CPA at baseline and at the end of anti-tubercular therapy. Of 255 initially recruited patients, 158 completed follow-up. The authors reported CPA at baseline and at end-of-treatment, with 23 of 158 assessed patients diagnosed with CPA at completion of TB therapy.

The study is important because it examined serial Aspergillus IgG changes and CPA incidence during the course of anti-tubercular therapy. The authors reported proven CPA in approximately 7% at baseline and 14.6% at end-of-treatment, broadly comparable with earlier Indonesian longitudinal data.

However, interpretation requires caution. Not all patients underwent HRCT at end-of-treatment, follow-up attrition was substantial, and the distinction between incident CPA, pre-existing CPA, transient Aspergillus immune response and radiological overlap with active TB remains difficult.

2. APICAL Indonesia study: CPA in patients treated for pulmonary TB

The APICAL study by Setianingrum and colleagues was a prospective longitudinal study in Indonesia. It investigated CPA in patients treated for pulmonary tuberculosis and reported CPA at baseline and at the end of TB therapy. Jha et al. cite APICAL as reporting 7.9% CPA at baseline and 13.3% at the end of TB therapy when proven and probable CPA were combined.

This study is one of the key pieces of evidence that the TB–CPA relationship is not purely post-treatment. CPA may be present within the treatment period, particularly where patients have cavitary disease or persistent symptoms.

3. Uganda study: persistent symptoms after two months of TB therapy

Namusobya and colleagues studied patients with microbiologically confirmed drug-sensitive PTB who had persistent respiratory symptoms after two months of standard anti-TB therapy. CPA was defined using persistent symptoms, suggestive radiology and evidence of Aspergillus infection, including Aspergillus IgG/IgM immunochromatographic testing and/or culture.

The study found CPA in around 20% of participants with persistent symptoms after the intensive phase of TB treatment. This is particularly relevant to clinical practice because two months is a natural review point in TB treatment pathways. Persistent symptoms at that stage are often interpreted as delayed recovery, adherence problems, drug resistance or alternative bacterial infection. CPA should be added to that differential in selected patients.

4. Ghana prospective follow-up: mainly post-treatment, but relevant to timing

Ocansey and colleagues followed patients after pulmonary TB treatment and found CPA emerging by the end of treatment and increasing further six months later. The study reported an overall 12-month CPA incidence of 10.7% among resurveyed patients, with 3% at end-of-treatment and 7.4% six months post-treatment.

This supports a continuum model: CPA risk may begin during active disease or treatment and continue after TB completion, especially in those with residual cavities.

Possible biological and diagnostic explanations

Detection of CPA during TB therapy may reflect more than one phenomenon. These categories are clinically important because they have different implications.

Diagnostic criteria: why timing is difficult

Most CPA definitions require compatible symptoms, radiology and mycological or immunological evidence over at least three months. That creates difficulty during TB therapy because active PTB itself can produce prolonged symptoms and cavitary radiology.

Guideline-consistent CPA diagnosis generally requires:

• chronic respiratory or systemic symptoms, usually for at least three months;
• compatible imaging, such as one or more cavities, pleural thickening, pericavitary infiltrates, fungal ball, progressive fibrosis or nodules;
• microbiological or immunological evidence of Aspergillus infection, especially raised Aspergillus IgG;
• exclusion of alternative diagnoses, including active TB, non-tuberculous mycobacterial disease, malignancy and other chronic infections.

In active TB, the exclusion criterion is problematic because TB and CPA can genuinely co-exist. Therefore, rather than using “active TB” to exclude CPA automatically, clinicians may need to ask whether the observed course is fully explained by TB alone.

When should CPA be considered during TB treatment?

CPA assessment should be considered during TB treatment when one or more of the following are present:

• persistent cough, haemoptysis, weight loss, fatigue or breathlessness after the intensive phase of TB treatment;
• persistent or enlarging cavities despite microbiological response to anti-TB therapy;
• new intracavitary material or suspected fungal ball;
• pleural thickening or pericavitary infiltrates that progress despite TB treatment;
• repeatedly negative TB microbiology despite a clinical label of TB relapse;
• history of previous TB or other structural lung disease;
• unexplained haemoptysis after apparent TB response;
• patients being considered for repeat TB treatment without strong microbiological confirmation.

Suggested diagnostic approach

A pragmatic diagnostic approach in specialist respiratory or infectious disease settings could include:

1. Confirm TB status: review baseline microbiology, GeneXpert/NAAT, culture, drug susceptibility and treatment response.
2. Repeat imaging: CT is preferable to chest radiography where CPA is suspected, particularly to assess cavities, fungal ball, pleural thickening and pericavitary progression.
3. Request Aspergillus IgG: a positive result is a major diagnostic component, though not sufficient alone.
4. Send respiratory samples: fungal culture and/or Aspergillus PCR where available; also reassess for TB and non-tuberculous mycobacteria.
5. Assess duration and trajectory: progressive symptoms or radiology over three months strengthens CPA diagnosis.
6. Review differential diagnoses: malignancy, bacterial bronchiectasis, NTM, lung abscess, vasculitis and other chronic infections.
7. Discuss complex cases with a specialist mycology or CPA centre: especially if antifungal therapy is being considered during rifampicin-based TB treatment.

Treatment implications and drug interactions

If CPA is diagnosed during TB therapy, management is complicated by major drug interactions. Rifampicin is a potent enzyme inducer and substantially reduces exposure to many triazole antifungals, including itraconazole, voriconazole and posaconazole. Co-administration is generally problematic and may render azole therapy ineffective.

Specialist input is therefore essential. Management may require:

• review of TB regimen and treatment phase;
• therapeutic drug monitoring for azoles where used;
• careful liver function monitoring;
• assessment of haemoptysis risk;
• consideration of timing of antifungal initiation;
• multidisciplinary discussion involving TB, respiratory, infectious diseases, pharmacy and mycology teams.

In some cases, observation and reassessment may be appropriate if CPA criteria are incomplete and the patient is clinically improving. In others, particularly with progressive cavitary disease, haemoptysis or strong Aspergillus IgG positivity, earlier specialist intervention may be justified.

What do guidelines currently say?

ERS/ESCMID

The ERS/ESCMID CPA guideline recognises tuberculosis as a major underlying condition for CPA and defines CPA using chronic symptoms, compatible radiology and Aspergillus evidence, typically over at least three months. It supports Aspergillus IgG as a central diagnostic test and recommends long-term oral triazole therapy for symptomatic or progressive chronic cavitary disease.

IDSA

The IDSA aspergillosis guideline similarly defines chronic cavitary pulmonary aspergillosis by at least three months of symptoms or progressive radiographic abnormalities, compatible cavitary disease, microbiological or serological evidence of Aspergillus, and minimal immunocompromise. It explicitly notes that CPA may complicate underlying pulmonary diseases, including tuberculosis and non-tuberculous mycobacterial infection.

BTS

The British Thoracic Society 2025 Clinical Statement on Aspergillus-related chronic lung disease provides current UK best-practice framing for diagnosis and management of chronic Aspergillus lung disease. Its publication reflects increasing recognition that Aspergillus-related chronic lung disease requires specific diagnostic pathways, antifungal stewardship and specialist respiratory-mycology collaboration.

WHO TB guidance

WHO TB guidance focuses on TB diagnosis, drug susceptibility, treatment regimens, monitoring, treatment failure and public health control. CPA is not yet embedded as a routine screening component of standard TB treatment pathways. This creates a gap between TB programme algorithms and emerging evidence from fungal disease studies.

Evidence strength

Implications for TB and respiratory services

The emerging evidence supports a targeted CPA assessment trigger within TB pathways, rather than universal screening at present.

A reasonable specialist position would be:

In patients receiving treatment for pulmonary tuberculosis, persistent symptoms, haemoptysis or non-resolving/progressive cavitary disease after the intensive phase should prompt consideration of CPA, especially where TB microbiology is negative or improving and imaging remains suspicious.

This is particularly relevant in high TB burden countries, but also in low TB burden settings where patients with previous TB, migrant health histories or unexplained cavitary disease may be seen in respiratory clinics.

Research priorities

• Prospective studies with baseline and serial CT imaging in microbiologically confirmed PTB.
• Serial Aspergillus IgG titres, fungal culture and molecular testing during TB therapy.
• Clear separation of proven CPA, probable CPA, Aspergillus colonisation and transient seropositivity.
• Studies of CPA screening at two months versus end-of-treatment versus six months post-treatment.
• Outcome studies assessing whether early CPA recognition reduces haemoptysis, lung destruction, retreatment for TB or mortality.
• Health-economic modelling of targeted CPA testing in TB programmes.

Conclusion

The evidence base is moving from a simple post-TB model towards a continuum model of TB-associated CPA. In this model, Aspergillus-related disease may be present at TB diagnosis, emerge during therapy, become apparent at treatment completion, or develop later in post-TB lung disease.

For specialists, the key implication is not that every patient with TB requires CPA screening. Rather, CPA should be actively considered when the clinical trajectory is not adequately explained by TB alone, particularly in patients with cavitation, haemoptysis, persistent symptoms or poor radiological resolution.

Embedding a CPA assessment trigger into TB follow-up pathways may reduce misdiagnosis, repeated empirical TB treatment and delayed antifungal management. The evidence is not yet definitive, but it is strong enough to justify specialist awareness, targeted testing and further prospective research.

References

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7. Setianingrum F, Rozaliyani A, Adawiyah R, et al. A prospective longitudinal study of chronic pulmonary aspergillosis in pulmonary tuberculosis in Indonesia (APICAL).
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