Outcomes and outcome measures in studies of pulmonary alveolar proteinosis: a scoping review

Pulmonary alveolar proteinosis (PAP) is a rare lung disease characterised by progressive accumulation of surfactant-derived lipoproteinaceous material within alveoli, impairing gas exchange and causing respiratory insufficiency. Despite therapeutic advances such as whole lung lavage, substantial heterogeneity persists in outcome selection and reporting across studies, limiting comparability and evidence synthesis.

To systematically map and categorise outcomes and outcome measures reported in studies of PAP treatments and establish a foundation for developing a standardised core outcome set (COS).

A scoping review was conducted across four databases and two clinical trial registries (May 2024, updated May 2025). Eligible studies included those reporting treatment outcomes in patients of any age with PAP. Outcomes and measures were extracted and categorised using the Core Outcome Measures in Effectiveness Trials taxonomy.

From 8475 screened records, 62 studies met the inclusion criteria, encompassing 31 distinct outcomes and 92 corresponding outcome measures. Physiological parameters dominated reporting, including arterial oxygenation (n=55, 89%; such as arterial oxygen tension and alveolar-arterial oxygen gradient) and lung function indices (n=53, 85%; such as diffusing capacity of the lung for carbon monoxide and forced vital capacity) were most frequently assessed. In contrast, patient-centred outcomes such as quality of life were reported in only 10 (16%) studies, while adverse events were relatively well-reported (n=41, 66%).

The reporting of outcomes and outcome measures in PAP studies is highly variable. There is an urgent need for a COS tailored to PAP that focuses on physiological outcomes, adverse events and patient-reported outcomes.