Background : Gout is the most prevalent arthritis globally, it is due to monosodium urate crystals (MSU) deposit on tissues, mainly in joints and periarticular structures. Although the main clinical pattern in gout is monoarticular, many patients suffer from oligo/polyarticular crystalline deposits, even at the onset of the disease. Musculoskeletal US is a key tool for the diagnosis and treatment of these patients, due to its accessibility and safety. It determines accurately the current extent of deposits and joint involvement in gout, which may condition therapeutic changes.
Methods: Our objective was to evaluate the influence of articular US for clinical practice in Rheumatology when initiating treatment with febuxostat in patients with gout, determining the degree of crystalline deposit and articular ultrasonographic involvement, as well as the level of uricemia, at the time of initiation of treatment with febuxostat. We carried out an observational cross-sectional study of 450 patients diagnosed with gout according to ACR criteria from December 2013 toMay 2017. 129 out of 450 patients were treated with febuxostat (14 due to renal disease, adverse reaction or intolerance to allopurinol, and 115 due to lack of response to allopurinol), US examination was performed following the protocol proposed by Peiteado et al., determining the number of joints with signs of gout (double contour, hyperechoic aggregates, hyperechoic areas) as well as acute inflammatory activity (Doppler). Other variables were taken into account (age, sex, hypertension, diabetes mellitus, dyslipidemia, chronic kidney disease, time of disease evolution and clinical pattern of joint involvement). Statistics: descriptive analysis of variables. Calculation of Odds Ratio (OR) from the coefficients provided by a binomial logistic model and corresponding confidence interval. (R Statistics version 3.3.2).
Results: 115 patients with febuxostat (112 men and 3 women), with a mean age of 57 ± 13 years and mean of disease evolution 14 ± 10 years. 59 patients had monoarticular clinical pattern, 46 oligoarticular and 10 polyarticular. Regarding to US involvement: we observed acute inflammatory activity by Doppler in 47 patients (40.86%), microcrystalline aggregates in 90 patients (78.26%) and double contour sign in 53 patients (42.08%). The mean uricemia at the time of the joint ultrasound examination was 7.4 ± 1.8 g/dl. Of the 94 patients with uric acid levels> 6 mg/dl, 72 presented extensive US involvement (76.59%), whereas of the 21 patients with levels <6mg/dl, US involvement was observed in 18 (85,71%). From the observed variables, none was a risk predictor for joint involvement in the binomial logistic regression model. Uricemia presented OR=0.83 CI (0.6-1.1).
Conclusion: Musculoskeletal US allows a rapid and non-invasive assessment of the extent and intensity of crystalline joint deposit in patients diagnosed with gout, providing more information than traditional physical examination. In this study, patients with non-target uricemia did not present a greater joint affection evaluated by US, however, those with <6mg/dl, did present more affectation than might be expected. US examination of joints allows a more precise individualization of the treatment in gout and should be incorporated in a regulated way to a periodic evaluation of these patients to optimize their prognosis.