Can we Agree on the Diagnosis of ARDS?
February 1, 2000 3 minutes read
Can we Agree on the Diagnosis of ARDS?
Abstract & Commentary
In order to assess the extent to which a group of experts could agree on the radiographic diagnosis of acute lung injury (ALI) or the acute respiratory distress syndrome (ARDS), Rubenfeld and colleagues recruited 21 volunteers from the Toronto Mechanical Ventilation Workshop and the National Institutes of Health’s (NIH) ARDS Network, groups composed of clinical investigators with national or international reputations in this area. Rubenfeld et al showed each of these volunteers a series of 28 radiographs randomly selected at two medical centers from intubated patients with PaO2/FIO2 ratios of 300 mm Hg or less. In each instance, the volunteer was asked to indicate whether the findings on the radiograph were such that the criteria for diagnosing ALI or ARDS were met.
Interobserver agreement in applying the European-American Consensus Conference definition for ALI/ARDS was only moderate (kappa statistic, 0.55; 95% confidence interval, 0.52-0.57). Nearly complete agreement (20 or 21 readers in agreement) occurred for 13 of the radiographs (43%), while nine radiographs (32%) had at least five dissenting readers. The percentage of radiographs interpreted as consistent with ALI/ARDS by the individual readers ranged from 36% to 71%. The participants reported having the most difficulty with interpreting radiographs that showed mild infiltrates, pleural effusions, atelectasis, isolated lower lobe involvement, problematic radiographic technique, and overlying monitoring equipment. (Rubenfeld GD, et al. Chest 1999;116:1347-1353.)
COMMENT BY DAVID J. PIERSON, MD, FACP, FCCP
The European-American criteria for ALI/ARDS (Bernard GR, et al. Am J Respir Crit Care Med 1994;149:818-824) have been widely accepted by clinicians as a means for bringing much-needed consistency to the diagnosis of these common and important intensive care unit (ICU) disorders. These criteria are as follows:
1. Bilateral infiltrates consistent with pulmonary edema on frontal chest radiograph;
2. Acute hypoxemic respiratory failure:
ALI: PaO2/FIO2 = 300 mm Hg or less
ARDS: PaO2/FIO2 = 200 mm Hg or less;
3. Pulmonary arterial wedge pressure 18 mm Hg or less (or no clinical evidence of left atrial hypertension); and
4. Clinical setting consistent with ALI/ARDS.
It is sobering to learn that 21 acknowledged experts in diagnosing and managing ALI/ARDS demonstrated such relatively poor agreement in diagnosing these conditions from the same set of chest radiographs. If they can’t diagnose ALI/ARDS consistently, what about you and me?
This study illustrates one aspect of the "state of the art" in clinical recognition and management of ALI/ARDS. Clinicians have widely varying training and personal experience. We deal not with computer simulations or laboratory animals under carefully controlled conditions but with human beings, whose underlying physiognomy and health status varies and who come to us with a wide array of acute illnesses. When one adds the vagaries of positioning, exposure, and artifact that are routine with portable chest radiographs in critically ill patients, it is not too surprising that different clinicians see different things on a film.
The message here is not that this group of so-called experts did not really know their business, or that the diagnosis of ALI/ARDS is purely in the eye of the beholder and cannot be standardized. The appropriate message, as pointed out by Rubenfeld et al, is twofold: first, clinicians need to appreciate the imprecision with which even internationally accepted standards are applied in practice, and the effects this imprecision may have on the results of research studies; and, second, more work needs to be done in standardizing the radiographic criteria, perhaps including an annotated set of training radiographs analogous to those used in grading pneumoconioses.
When 21 acknowledged experts in diagnosing and managing ALI/ARDS were shown the same set of 28 chest radiographs, interobserver agreement on the presence or absence of ALI/ARDS was:
a. 0.42.
b. 0.55.
c. 0.64.
d. 0.78.
e. 0.92.
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