Identification of monosodium urate (MSU) crystals by microscopy remains the accepted gold standard for definitive diagnosis of gout. However, caveats include: suboptimal inter-observer agreement, lack of quantification of the extent of crystal deposition, and the impracticality of this method for diagnosis in primary care. In this presentation the pros and cons of different imaging methods for diagnosis, assessment and monitoring of gout will be discussed.
Plain radiography is readily available and can show the extent of joint damage from gout, but changes usually occur late, are largely non-specific and sensitivity of detection is low. Computed tomography (CT) and helical CT allow detection and quantification of tophi and bone erosions and dual energy CT (DECT) allows detection (with high specificity) and quantification of size and number of subclinical tophi – these techniques may also be useful in diagnosing atypical gout syndromes (e.g. radiculopathy from axial tophi). MRI can also demonstrate tophi, joint damage and associated inflammation, though specificity is low and aspirate confirmation is usually required. Ultrasound (US) can demonstrate bone erosions, tophi and the double-contour sign and although the specificity of these findings has been questioned US is a widely available imaging technique in clinical practice. DECT and US show promise in being able to monitor reduction in tophus size on urate lowering therapy in clinical trials. Raman spectroscopy is an interesting newly applied technique that currently being explored.
An important caveat to all imaging techniques is that they remain impractical in primary care where most gout patients are diagnosed and treated. Developing diagnostic methods that could be applied easily in this setting remains a priority.
Disclosure of Interest None declared