John D. FitzGerald

Aggregates are one of the elementary lesions seen on musculoskeletal ultrasound (US) in gout patients as defined by Outcome Measures in Rheumatology (OMERACT). The aim of this study was to evaluate the threshold of detection of aggregate findings on ultrasound and to analyze these findings with corresponding compensated light microscope (CPLM) images in vitro. Patient derived monosodium urate (MSU) crystals were obtained from two separate patients with gout during routine clinical care. In addition, fabricated in-house synthetic MSU crystals were used for comparison. Each sample was scanned using a GE Logic ultrasound machine and corresponding CPLM images obtained. As the aggregates became imperceptible by ultrasound, MSU clumping by CPLM examination was no longer detectable and crystal density per high power field fell markedly. Aggregates on US images are present only from patient-derived samples likely representing MSU crystal clustering or packing. Thus, when synovial aspiration is considered, a joint with aggregates on US would be a more suitable target with a higher likelihood of noting MSU crystals.