Volumetric reduction and dissolution prediction of monosodium urate crystal during urate-lowering therapy - a study using dual-energy computed tomography.

Methods: Baseline and follow-up DECTs were performed under a standard ULT protocol. Monthly dissolution rates were calculated by simple and compound methods. Correlations with average SU were compared and analyzed. Best-fit regression model was identified. MSU dissolution times were plotted against SU at different endpoints.
Results: In 29 tophaceous gout patients, MSU volume reduced from baseline 10.94 ± 10.59 cm ³ to 2.87 ± 5.27 cm ³ on follow-up ( p  = .00). Dissolution rate had a stronger correlation with SU if calculated by compound method (Pearson's correlation coefficient r = -0.77, p  = .00) and was independent of baseline MSU load. The ensuing dissolution model was logarithmic and explained real-life scenarios. When SU > 0.43 mmol/l, dissolution time approached infinity. It improved to 10-19 months at SU = 0.24 mmol/l. When SU approximated zero (as with pegloticase), dissolution flattened and still took 4-8 months.
Conclusion: MSU dissolution is better described as a logarithmic function of SU, which explains, predicts, and facilitates understanding of the dissolution process.