Imaging modalities for the classification of gout: systematic literature review and meta-analysis

Abstract

Background: Although there has been major progress in gout imaging, no gout classification criteria currently include advanced imaging techniques.

Objective: To examine the usefulness of imaging modalities in the classification of gout when compared to monosodium urate (MSU) crystal confirmation as the gold standard, in order to inform development of new gout classification criteria.

Methods: We systematically reviewed the published literature concerning the diagnostic performance of plain film radiography, MRI, ultrasound (US), conventional CT and dual energy CT (DECT). Only studies with MSU crystal confirmation as the gold standard were included. When more than one study examined the same imaging feature, the data were pooled and summary test characteristics were calculated.

Results: 11 studies (9 manuscripts and 2 meeting abstracts) satisfied the inclusion criteria. All were set in secondary care, with mean gout disease duration of at least 7 years. Three features were examined in more than one study: the double contour sign (DCS) on US, tophus on US, and MSU crystal deposition on DECT. The pooled (95% CI) sensitivity and specificity of US DCS were 0.83 (0.72 to 0.91) and 0.76 (0.68 to 0.83), respectively; of US tophus, were 0.65 (0.34 to 0.87) and 0.80 (0.38 to 0.96), respectively; and of DECT, were 0.87 (0.79 to 0.93) and 0.84 (0.75 to 0.90), respectively.

Conclusions: US and DECT show promise for gout classification but the few studies to date have mostly been in patients with longstanding, established disease. The contribution of imaging over clinical features for gout classification criteria requires further examination.

Keywords: Arthritis; Gout; Ultrasonography.

Conflict of interest statement

COMPETING INTERESTS

None declared.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Figures

Figure 1. Search results

Ovid Medline, PubMed, Embase, and Cochrane databases were searched using the search strategy in the appendix. In addition, proceedings from the American College of Rheumatology (ACR) and European Union League Against Rheumatism (EULAR) annual meetings from 2007–2012 were searched for relevant abstracts.

Figure 2. Methodologic quality as assessed using the QUADAS tool

The vertical access contains the individual quality metrics and the horizontal access reflects the proportion of studies meeting these criteria (in green). Yellow signifies that it was unclear whether the study met the quality metric (usually because it was reported) and red signifies that the study specifically did not meet that metric.

Figure 3. Hierarchical summary receiver operator curves (HSROC)

Hierarchical summary receiver operating characteristic curve for a) ultrasound double contour sign, b) tophi on ultrasound, and c) DECT. The closed points represent the individual studies in the review. The open point represents the pooled sensitivity and specificity estimate and the enclosed shape represents the bivariate 95% confidence interval for the pooled sensitivity and specificity estimate.