Quantifying diffuse airspace disease on portable chest radiographs in acute respiratory failure using the RALE score

Area of Science:

• Critical Care Medicine
• Radiology
• Pulmonary Medicine

Background:

• Portable chest radiographs (CXRs) are crucial for assessing airspace disease (ASD) in acute respiratory failure (ARF).
• The Radiographic Assessment of Lung Edema (RALE) score offers semiquantitative ASD assessment but its utility across diverse ARF types is unclear.

Purpose of the Study:

• To evaluate the RALE score's ability to quantify radiographic ASD burden in various ARF subtypes.
• To determine if RALE can distinguish between the presence and absence of ASD, and stratify its extent.

Main Methods:

• Analysis of 4,259 portable CXRs from 814 critically ill adults with expert-adjudicated ARF subtypes.
• Trained clinicians assigned RALE scores, blinded to clinical data.
• Receiver operating characteristic curves evaluated discrimination, with sensitivity analyses for image quality.

Main Results:

• RALE scores increased stepwise with ASD severity, discriminating ASD-absent from ASD-present CXRs (AUC 0.81).
• RALE quantified diffuse opacification with moderate accuracy (AUC 0.79) but overlapped across ARDS, cardiogenic edema, and AE-ILD.
• Suboptimal image penetration significantly reduced RALE's discriminatory power.

Conclusions:

• RALE effectively quantifies radiographic ASD burden and stratifies parenchymal involvement in ARF.
• RALE is a metric of radiographic burden, not a specific diagnostic classifier.
• Accurate RALE scoring necessitates adequate image quality and interpretation within the clinical context.