Sensitivity and specificity of ultrasonographic features of gout in intercritical and chronic phase

This study aimed to assess the sensitivity and specificity of ultrasonographic features of gout in intercritical and chronic stages and compared ultrasonographic features of gout between patients with persistent high serum uric acid (SUA) and patients with low SUA.

Adult patients with gout confirmed by demonstration of monosodium urate crystals were recruited, if they were in intercritical or chronic stage clinically. Ultrasonographic examination of the first metatarsophalangeal joints (MTPJs) and the knee joints of both sides were done by a blinded rheumatologist trained in musculoskeletal ultrasound.

Sixty-two patients with gout and 30 control subjects were examined. The double contour sign (DCS) was found in 71 (57.3%) first MTPJs and tophi were found in 54 (43.5%) first MTPJs. DCS was present in 43 (69.4%) gout patients but none in the control group (P < 0.001). Sensitivity and specificity (95% CI) of DCS in gout patients were 69.4% (56.4-80.4%) and 100% (88.3-100%), respectively, while of tophi they were 66.1% (53-77.7%) and 100% (88.3-100%), respectively. The sensitivity of DCS increased to 100% in high the SUA subgroup (SUA ≥ 7 mg/dL). The low SUA (SUA < 7 mg/dL) gout subgroup showed significantly higher occurrence of erosions (40%) and tophi (50%) in first MTP joints than the control group.

MSUS is useful for diagnosis of gout in intercritical or chronic stages, especially in patients with persistently high SUA level.