A Delphi Exercise to Identify Characteristic Features of Gout – a Study of Opinions from Patients and Physicians to Inform New Classification Criteria

Background/Purpose: Updated classification criteria for gout are required. The aim of this study was to identify a comprehensive list of features that might discriminate between gout and similar conditions, for use in a subsequent case-control study for developing and testing new classification criteria.

Methods: Two Delphi exercises were conducted using web-based questionnaires; one with physicians who have an interest in gout and one with patients who have gout. Physicians rated a list of potentially discriminating features that were identified via literature review and expert opinion and patients rated a list of features that they generated themselves. Agreement was defined by the RAND/UCLA disagreement index. Multiple iterations were conducted until consensus was reached or no changes in participant ratings were observed.

Results: Forty-four highly experienced physicians (62% response rate) and nine patients (11% response rate) responded to all iterations.  For physicians, 71 items were identified by literature review and 15 more were suggested by physicians.  The physician survey showed agreement for 26 discriminatory features and 15 that were not discriminatory.  The patients identified 46 features of gout for which there was agreement on 25 items as being discriminatory and seven items being not discriminatory. The results of highly rated features for both physician and patient surveys are summarised in the Table (showing areas of agreement and disagreement). Patients and physicians agreed upon several key features of gout: suddenness of onset, redness, marked tenderness and swelling of the affected joint, elevated serum urate levels, presence of tophi, presence of urate crystals in synovial fluid and involvement of the first metatarsophalangeal joint.  Physicians emphasized imaging and patterns of symptoms, whereas patients emphasized functional impact, dietary triggers and idiographic perception of symptoms.

Conclusion: Physicians’ and patients’ perceptions of the key features of gout have some similarities but many differences.  The list of features with a median rating of 7 to 9, generated by both patients and physicians, will be examined in a case-control study to identify the most sensitive and specific combination for the classification of crystal-proven gout.

Table: The overlap and differences between features highly rated (median 7 to 9) by physicians and patients. US: ultrasonography, CT: computed tomography, DECT: dual energy CT, MRI: magnetic resonance imaging