Original ArticleDevelopment of a clinical definition for acute respiratory distress syndrome using the Delphi technique
Introduction
There is no available diagnostic test to confirm the presence of acute respiratory distress syndrome (ARDS), and it is, therefore, defined by clinical criteria in a similar fashion to diseases such as rheumatoid arthritis and depression. Unlike many rheumatologic and psychiatric diseases, however, very little work has been done to develop and test standardized diagnostic criteria for ARDS [1]. Indeed, for many years after its original description [2], ARDS remained a gestalt diagnosis without specific criteria [3].
Translating the pathophysiologic concepts of ARDS [4], [5], [6], [7], [8], [9] into a working clinical definition has proved challenging. The widely used American-European Consensus Conference (AECC) definition requires the acute onset of hypoxemia and bilateral chest x-ray infiltrates in the absence of left atrial hypertension [10]. This definition has not performed well in limited reliability testing focusing on the chest radiograph [11], [12], and the agreement between this definition and the autopsy findings of ARDS is only moderate [13]. The recognition that rigorously developed and validated diagnostic criteria are vital to the performance of clinical trials in this area has led to calls for a reevaluation of this definition [14], [15], [16], [17].
The use of formal consensus techniques in medicine is becoming increasingly frequent, but in critical care, these have typically taken the form of consensus statements used to help guide clinical care [18], [19], [20], [21], [22], [23], [24]. Formal consensus techniques may be helpful in explicating the necessary judgmental approach to definition development in situations where no gold standard exists, potentially reducing bias and resulting in a definition with improved operating characteristics. The AECC definition, however, was created without the use of formal consensus techniques. We are unaware of any reports documenting the use of such methodologies in the derivation of definitions for ARDS or other clinical entities in critical care. A variety of formal methods is available when conducting a consensus process [19], [25], [26], [27]. One such method is the Delphi technique, an iterative process where experts are polled individually with a series of questionnaires, receiving anonymous group feedback between iterations [19]. In this paper, we describe the use of the Delphi technique in the development of a new ARDS definition. This represents the first phase of a strategy to develop and test a novel ARDS definition using rigorous methodologies.
Section snippets
Design
The Delphi technique was chosen over other consensus techniques because of its ability to overcome temporal and geographic constraints, low cost, and ability to ensure all the panelists an equal voice in the proceedings. Approval from the University of Toronto research ethics board was obtained.
Participants
A systematic method for identifying individuals who were both opinion leaders and clinical researchers was used to avoid bias in the selection of panelists [28]. First, opinion leaders were gathered by
Participants
The first 16 individuals who were approached agreed to participate in the consensus process. However, 11 (69%) of the 16 panelists actually participated in the definition development. Their names are listed in the acknowledgements. Demographic information on the participants is shown in Table 2.
Item generation—Delphi round 1
The first Delphi questionnaire, asking panelists to identify all possible defining characteristics for inclusion in a new ARDS definition, yielded 10 possible defining characteristics (Table 3). The
Discussion
Definitions for difficult-to-define intensive care unit (ICU) clinical entities such as sepsis, ventilator-associated pneumonia, and ARDS have not been approached previously using formal consensus techniques. Papers labeled as “consensus conferences” have been published addressing each of these examples, but in each case, the format used was an informal group discussion. Formal consensus methods, such as the Delphi technique, may be useful in reducing bias and enhancing the transparency of the
Acknowledgments
This study was supported in part by the Canadian Institutes of Health Research/Canadian Lung Association (Ottawa, Ontario, Canada) Post-Doctoral Fellowship (Dr Ferguson) and the Health Career Award from the Canadian Institutes of Health Research (Dr Davis). We thank the following individuals who participated as members of our expert panel during the Delphi process: Drs Antonio Artigas, Jean-Daniel Chiche, Gregory Downey, Margaret Herridge, Waldemar Johanson, Marin Kollef, James Lewis, Neil
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