Background Studies, reporting specificity of ultrasonographic (US) features of gout, such as double contour sign (DC) and tophus (T) ranges from 72-91% and 34-87% respectively. Most studies are done with gout for an average duration of symptoms of 7 years. There is lack of data about the Us features in the early disease.
Objectives To search for the US changes, such as double countour sign, tophi and erosiones in the multiple joints and 2 tendons, to assess the diagnostic value of these features in the early gout and to compare the findings with the established disease.
Methods 51 “clinical gout” and 19 asymtomatic according joints individuals were screened for US changes during the 12 months period in the prospective study. Synovial fluid investigations were done to all individuals with pathological US changes, specific to gout, who agreed with the intervention. All subjects underwent polyarticular (32 joints) and 2 tendons (patellar and triceps) 2D US in grey scale mode by 1 rheumatologist, trained in the US with the experience of >10 years, blinded to the group of participants and their clinical data. The 100 saved, randomly selected US pictures were evaluated by another rheumatologist with 3 years of US experience to check the concordance between the investigators. The specificity and sensitivity was counted in the crystal proven gout. The controls were selected from asymptomatic: normouricemic (15 cases), hyperuricemic with no US symptoms of gout (2) or with some features on US, but crystal free in the synovial fluid hyperuricemic (1 case) participants.
Results Urate crystals found in the 38 (73.1%) gout cases and none in the investigated controls. 12 crystal proven patients (10 men), age 53.3±11.7 with disease duration 1.1±0.71 were classified as early and 40 patients with disease duration of 11.8±8.6 - as advanced gout with uric acid level 493±126 μM and 483.4±142 respectively (no signifficant difference). The mean number of attacks per year did not differ between the early and established gout 12 (1-20) and 15, respectively. The total number of gout attacks per life was bigger in the advanced group (p<0.005). No difference was achieved according the tophus, “found in at least 1 site”, between the groups. There was statistical difference between the groups in the mean number of DC found per patient, 3.1 and 5.7 in the early and established gout, respectively (p 0.002). The (US) tophus was observed in at least one anatomical site in 91.7% in the early group, mostly in the metatarsophalangeal joints. The DC was found in 66.7% in the early versus 95% in the advanced gout.The specificity for DC and T was 88% and 77% respectively in the early gout. Erosiones were found in 58.3% in the early gout.The concordance between readers was good.
Conclusions The specific gout symptoms, such as tophus and double contour sign can be detected with acceptable sensitivity in early gout, the DC being less sensitive, but more specific. The number of tophi increases with the duration of the disease. More randomized studies, with bigger numbers of patients are required to definitely validate these US changes in early gout.
Optimising ultrasonography in rheumatology. Clin Exp Rheumatol. 2014 Sep-Oct;32(5 Suppl 85):S-13-6. Epub 2014 Oct 30.
Disclosure of Interest None declared