| Modality | Description | Limitation |
| Clinical | ||
| Symptoms and signs | Increased cough, sputum production/volume or purulence, dyspnoea, lethargy, haemoptysis, chest pain70 or deterioration in chest signs | Perception issues74 and likely insensitive |
| Lung function | ||
| Spirometry | Classically obstructive, easy to do and use when aged >6 years | Insensitive and patients can have structural airway changes on HRCT despite normal spirometry75 |
| QOL | SGRQ validated for bronchiectasis71 and used in studies29 69 76 | No bronchiectasis-specific QOL exists |
| Radiology | ||
| Chest radiograph | Increased markings, lesions, scarring, atelectasis77 | Poor sensitivity78 |
| HRCT scan | Many scoring systems for bronchiectasis exist,79 80 81 “best” unknown. Exacerbation frequency related to bronchial wall thickening31 | Impractical for regular use; issues with radiation dose,82 especially in children83 |
| Airway inflammation/oxidation | ||
| Exhaled H2O2 | Elevated in bronchiectasis, negative correlation with FEV184 | More studies required Steroids have no effect on H2O2 |
| Exhaled CO | Elevated in bronchiectasis85 | More studies required |
| Exhaled NO | Decreased, normal and increased86 values described. Correlation with disease severity if not on steroids86 | Inconsistent data. Sensitivity unknown, currently unsuitable as a monitoring tool for bronchiectasis. |
| Sputum indices | Airway neutrophilia reduces with antibiotic treatment,59 tumour necrosis factor α, interleukin-8, neutrophil elastase also decreases with antibiotics59 | Useful when asthma or ABPA87 suspected as cause of exacerbation; eg, if eosoinophilia present, systemic corticosteroids likely to be beneficial |
| AHR | ||
| Methacholine | Increased AHR47 | Direct tests for AHR increasingly recognised to be non specific88 |
| Cardiac assessment | Left ventricular diastolic dysfunction.89 Correlates with disease severity | No prospective medium/long term cohort available to define role |
| Exercise test | Decreased exercise tolerance,90 lower aerobic capacity and maximal ventilation91 | No prospective medium/long-term cohort available to define role |
ABPA, allergic bronchopulmonary aspergillosis; AHR, airway hyper-responsiveness; CO, carbon monoxide; FEV1, forced expiratory volume in 1 s; H2O2, hydrogen peroxide; HRCT, high-resolution computed tomography; NO, nitric oxide; QOL, quality of life; SGRQ, St George’s respiratory questionnaire