A chest x-ray scoring system called the Radiographic Assessment of Lung Edema (RALE) can accurately identify acute respiratory distress syndrome (ARDS) in invasively ventilated ICU patients, researchers have reported. 

The finding suggests the system could help standardize approaches for interpreting chest x-rays in these patients, which currently relies on a subjective judgment influenced by radiograph quality, training, and experience, according to an international group led by Lorraine Ware, MD, of Vanderbilt University in Nashville, TN. 

"[Chest x-rays] are widely accessible and routinely obtained in critically ill patients, and, despite well-recognized limitations in depicting lung pathology, remain central to all past and current ARDS definitions," the group wrote. "Standardized approaches to their interpretation are therefore needed." The study was published October 21 in Critical Care Explorations. 

The RALE score is a semi-quantitative system developed in 2018 to quantify the extent and density of pulmonary edema on chest x-rays. It was not designed as a diagnostic tool for ARDS, and studies of its diagnostic accuracy in patients with the syndrome remain scarce, the researchers noted. 

For the analysis, the researchers drew on data from the Validating Acute Lung Injury Biomarkers for Diagnosis study, a prospective observational cohort of adult patients receiving invasive ventilation for at least two consecutive days at Vanderbilt University Medical Center. Chest x-rays from the first two ICU days were scored independently using the RALE system by at least two experienced raters. The highest average score from either day was selected for analysis. The primary outcome was ARDS during the first two ICU days. 

Of 236 patients, 92 (39%) had ARDS. The median RALE score was significantly higher in patients with ARDS than in those without (29.5 versus12.2), the authors found. The score showed excellent diagnostic accuracy with an area under the receiver operating characteristic curve of 0.93. At an optimal cutoff of 20, sensitivity was 85%, specificity was 83%, positive predictive value was 76%, and negative predictive value was 90%, the researchers reported. Interobserver reliability was high, with pairwise intraclass correlation coefficients ranging from 0.81 to 0.87, they added. 

"The RALE score accurately identified ARDS in this cohort of invasively ventilated patients and demonstrated excellent interobserver agreement," the authors wrote. 

The group noted that the most recent global ARDS definition retained bilateral opacities on chest x-rays as a core criterion, but stopped short of incorporating formal radiographic scoring systems such as the RALE score, pending prospective validation. 

"Our findings represent a step toward the validation that such integration would require," the authors concluded. 

The full study is available here.