Outcome measure | Indications, advantages | Limitations |
---|---|---|
Pulmonary function | - Suitable for long-term studies. - Conventional PFT (i.e. spirometry, body plethysmography): valid measures, reference equations and extensive guidelines available. | - Inappropriate to detect acute changes related to ACTs. - Pulmonary function is measured as a single unit (‘black box’ principle). No regional abnormalities or changes can be detected. - Conventional PFT: insensitive to mild lung disease. - Age appropriate approach required. - The potential of PFT in infants and preschoolers remains unclear. |
Expectorated sputum | - Sputum quantity gives an impression of mucus transport in short-term studies. | - Sputum quantity: inaccurate, unreliable, unsuitable for uncooperative children. |
Oxygen measurements | - Provides information about the presence of a ventilation-perfusion mismatch. - ABG analysis is the ‘gold standard’ method to measure blood oxygenation status. - Pulse oximetry is suitable for continuous monitoring and is simple to perform. | - ABG analysis requires invasive sampling. - Pulse oximetry is too imprecise for research purposes to detect small changes. - Oxygenation as an outcome is not suitable for children with mild lung disease in stable conditions. |
Exercise capacity | - Adequate for long-term studies focused on pulmonary rehabilitation. | - Exercise capacity cannot be measured in children <6y. - Inappropriate to evaluate short-term effects of airway clearance. - Inadequate to measure solely the effects of airway clearance. |
Imaging | - Detailed regional information of the lungs. - Hyperpolarized MRI is sensitive to changes in ventilation distribution. - RAT technique is the most direct technique to quantify acute changes in mucus transport. | - Chest X-rays lack sufficient sensitivity. - CT imaging is associated with radiation exposure. - Subjectivity of scoring methods. - Limited availability and high cost of most techniques. |
Disease exacerbation parameters | - Demonstrate the impact on pulmonary exacerbations, which is a direct clinical endpoint. - No complex testing material is required to achieve this information. | - Only relevant for long-term studies. |
Patient-reported outcomes | - The inclusion of PROs promotes a patient-centered model of care. - The perception and preference of the patient will influence adherence to the therapy, which emphasizes the importance of PROs for the evaluation of ACTs. | - There are a large number of PROs available, but not all PROs are validated and therefore results should be interpreted with caution. - High risk of bias if subjects are not blinded to the therapy. |