Urate crystal deposition in asymptomatic hyperuricaemia and symptomatic gout: a dual energy CT study

Background The aim of this study was to compare the frequency and volume of dual energy CT (DECT) urate deposits in people with asymptomatic hyperuricaemia and symptomatic gout. Methods We analysed DECT scans of the feet from asymptomatic individuals with serum urate >= 540 mu mol/L (n= 25) and those with crystal proven gout without clinically apparent tophi (n= 33). Results DECT urate deposits were observed in 6/25 (24%) participants with asymptomatic hyperuricaemia, 11/14 (79%) with early gout (predefined as disease duration <= 3 years) and 16/19 (84%) with late gout (p< 0.001). DECT urate deposition was observed in both joints and tendons in the asymptomatic hyperuricaemia group, but significantly less frequently than in those with gout (p <= 0.001 for both joint and tendon sites). The volume of urate deposition was also significantly lower in those with asymptomatic hyperuricaemia, compared with the early and the late gout groups (p< 0.01 for both comparisons). Similar urate volumes were observed in the early and late gout groups. Conclusions Although subclinical urate deposition can occur in people with asymptomatic hyperuricaemia, these deposits occur more frequently and at higher volumes in those with symptomatic gout. These data suggest that a threshold of urate crystal volume may be required before symptomatic disease occurs.