A Study Measuring Markers of Airway Inflammation in Breath Samples From People With Respiratory Diseases and Healthy Volunteers.

Inclusion Criteria:

\- 1. Age: Adults aged ≥18 years. 2. Consent: Willing and able to provide written informed consent (prospective participants only).

3\. Clinical status: Belong to one of the defined diagnostic categories listed below:

1. Group A: Lung cancer confirmed by multidisciplinary team (MDT) diagnosis.
2. Group B: Suspected lung cancer (biopsy negative or awaiting further investigation).
3. Group C: Pneumonia (radiologically or clinically confirmed).
4. Group D: Non-malignant airways diseases (asthma or COPD).
5. Group E: Other non-malignant respiratory diseases (interstitial lung disease, bronchiectasis, breathing pattern disorder).
6. Group F: Healthy controls with no known respiratory disease. 4. Clinical documentation: Availability of relevant diagnostic and demographic data to confirm disease classification (for retrospective participants).

   5\. Previous participation: Individuals previously enrolled in the VICTORY or ExPeL studies may be included for retrospective data integration.

   6\. Willing and able to perform a breath test using the Inflammacheck® device. 7. Willing to allow access to relevant clinical data and imaging results 8. Be able to understand and communicate in English with or without the need for a translator, to ensure informed consent and comprehension of study procedures

   Exclusion Criteria:
   * 1\. Active respiratory infection (e.g., tuberculosis, bronchopneumonia) other than pneumonia (e.g., tuberculosis) at the time of breath sampling.

     2\. History of major thoracic surgery or lung resection within the previous six months.

     3\. Current or recent chemotherapy or radiotherapy for lung cancer at the time of breath sampling (except for retrospective confirmed cancer cases where data were collected pre-treatment).

     4\. Severe cognitive impairment, communication barriers, or any condition preventing informed consent or compliance with study procedures.

     5\. Pregnancy or breastfeeding. 6. Active use of cannabis or recreational drugs known to alter exhaled breath composition.

     7\. Current active tobacco smoking within the past 12 hours prior to breath collection will be an exclusion criterion, as will the use of vaping or e-cigarettes within this period, to prevent contamination of exhaled breath samples 8. Participants who have taken systemic antibiotics or commenced a new course of oral or inhaled corticosteroids within the preceding two weeks will also be excluded, as these may transiently alter inflammatory biomarkers in exhaled breath (this is not applicable to participants with pneumonia). Stable use of maintenance inhaled corticosteroids in patients with chronic respiratory conditions (e.g., asthma, COPD) will be permitted, provided dosing has remained unchanged for at least four weeks prior to sampling.

     9\. Any condition that, in the opinion of the investigator, could compromise participant safety or the integrity of the data.

     10\. Unable or unwilling to provide informed consent. 11. Unable to complete the breath test due to physical or cognitive limitations.

     12\. Currently participating in another interventional clinical trial that may confound breath biomarker data.

     13\. Received systemic treatment for lung cancer prior to breath sampling (for the lung cancer group only).

     14\. History of any active cancer within the past 12 months (excluding basal cell carcinoma of the skin or cervical carcinoma in situ), except for those in the confirmed lung cancer group.

     15\. They have any active respiratory infection other than pneumonia (e.g., tuberculosis) at the time of breath sampling.

     16\. They have undergone a bronchoscopy or invasive respiratory procedure within the past 48 hours, due to the potential for artefacts in breath data.

     17\. Pneumonia with concurrent lung cancer, thoracic malignancy or lung fibrosis. Pneumonia with co-existent asthma or COPD can be included at discretion of the PI.