The presence of bilateral lung infiltrates on chest imaging is a mandatory clinical criterion for the diagnosis of acute respiratory distress syndrome (ARDS). Although lung infiltrates are usually identified on chest radiograph in clinical practice, chest computed tomography (CT) outperforms chest radiograph for the diagnosis of lung infiltrates. We hypothesized that the performance of chest radiograph for the diagnosis of ARDS, as compared to chest CT as reference, is limited.

We conducted a retrospective, single-center, observational study over a 7-year period, including patients who met all but the imaging criterion for ARDS (defined by the Berlin criteria) and who underwent a chest CT and a chest radiograph the same day. Chest CT was interpreted by two radiologists and considered as the gold standard diagnosis of ARDS whereas chest radiographs were interpreted by two intensivists. The primary outcome was the agreement between chest radiograph and chest CT for the diagnosis of ARDS in the overall population. Secondary outcomes included the performance of chest radiograph for the diagnosis of ARDS in the overall population and in predefined subgroups, especially based on patient characteristics, imaging features, timing between chest radiograph and CT, and inter-rater agreement. Agreement was assessed using Cohen’s kappa, and diagnostic performance using sensitivity, specificity, predictive values, and accuracy for the primary outcome and subgroup analyses.

Out of the 277 patients included during the study period, prevalence of ARDS on chest CT among hypoxemic intubated patients fulfilling all but the imaging criteria for ARDS was 81%. Overall, the agreement was fair to moderate and consistent across subgroups. Sensitivity of chest radiograph for the diagnosis of ARDS ranged from 74% to 80%, higher in patients with four quadrants involved on chest radiograph (100%), and lower in patients with focal ARDS on chest CT (54–67%).

Chest radiograph has limited performance for the diagnosis of ARDS, and at least 20% of patients with ARDS on chest CT were not diagnosed using chest radiograph. Systematic chest CT in hypoxemic intubated patients may reduce the under-recognition of ARDS and contribute to effective implementation of protective ventilation strategies.