Background Recently, ultrasonography (US) demonstratted its ability to detect urate deposition in gouty patients. Some US features have been suggested to be specific such as tophus and the double contour sign. In contrast to the usefulness of US for diagnosis, data are lacking on its place in follow-up of gout deposition after initiation of urate-lowering therapy (ULT).
Objectives We aimed to determine the ability of US to show disappearance of urate deposits in gouty patients requiring ULT.
Methods To be included in this prospective single-centre study, patients needed to exhibit 1) proven gout by crystals in synovial fluid and 2) US-evidenced urate deposits (double contour [DC] sign and/or tophi) before starting ULT. At baseline and after 6 months of ULT, one trained ultrasonographer assessed the knee and first metatarsophalangeal (MTP1s) joints. Serum uric-acid (SUA) level was assessed at baseline and at 3 and 6 months after ULT initiation. Correlation between US findings and achievement of SUA level objective (<360 μmol/l) was estimated by the kappa coefficient (k).
Results We studied 16 patients (all males, mean age 61.0±18.3 years). The mean disease duration was 7.1±6.2 years. Tophi were found at clinical exam in 56% of patients. Baseline SUA levels were 688±153 μmol/l. At baseline, US revealed tophi or a DC sign among 62.5% to 75% of patients in knees and 87.5% in MTP1s. Among 3 of the 4 patients not achieving the SUA level objective, US features had not disappeared. Among the remaining 12 patients, US features disappeared or decreased in all but one with a stable DC sign in one MTP1. The correlation between the whole US examination and SUA level was excellent (k=0.875).
Conclusions Our results suggest that screening for specific features of gout such as tophi or DC sign by US at the initiation of ULT and during follow-up is a sensitive way to detect the disappearance of urate deposits in gout. Moreover, correlation was good between modification of US-observed features of gout and SUA levels decreased to below the recommended SUA objective. Although these findings are promising, future randomized studies with a large number of patients are required to definitely validate US assessment for gout treated with ULT.
Disclosure of Interest None declared