Interobserver Variability in Applying a Radiographic Definition for ARDS
Since the original description of ARDS in 1967, the chest radiograph has been an essential part of its definition. In the initial report, the chest radiograph was described as presenting “patchy, bilateral alveolar infiltrates.” Since then, a variety of radiographic criteria have been described in the definition of acute lung injury (ALI)-ARDS, including “reduction in the longitudinal pulmonary diameter,” “interstitial and alveolar edema,” and at least two radiographic scoring methods.
Critics have hypothesized that the variability in reports of the incidence, risk factors, and outcomes of ARDS were due in part to poorly characterized definitions and to heterogeneous patient popula-tions. To address this problem and to set standard definitions, an American-European Consensus Conference (AECC) was convened in 1992. In their report, members of the conference defined ALI as the acute onset of arterial hypoxemia (Pa02/fraction of inspired oxygen [Fio2] ratio, < 300), a pulmonary artery wedge pressure < 18 mm Hg or no clinical evidence of left atrial hypertension, and bilateral infiltrates consistent with pulmonary edema on frontal chest radiograph. The authors specifically noted that the pulmonary infiltrates could be mild. ARDS is defined by the same criteria as ALI, but with more severe hypoxemia (Pa02/Fl02, < 200). No radiographic distinction was made between ALI and ARDS, and therefore, for this report, we will refer to a common entity, ALI-ARDS. more
Interobserver variability in the interpretation of diagnostic radiograph has been reported by a number of investigators. Evaluations of mammograms, ventilation-perfusion scans, and chest radiographs in cases of pneumonia and pneumoconiosis may demonstrate poor agreement between readers. We hypothesized that the AECC radiographic definition was not specific enough to lead readers to a reliable and reproducible interpretation of chest radiographs. Therefore, in applying the definition, we hypothesized that there would be a wide range of individual thresholds for determining that the infiltrates were consistent with pulmonary edema and interobserver variability.