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Ultrasonography yielded sensitive, specific diagnosis for gout
Ultrasound provided sensitivity and specificity in diagnosing gout, according to study results.
Researchers investigated 53 patients with crystal-proven gout (mean age, 59.7 years; 92% men) and 50 control subjects (mean age, 59.5 years; 80% men) in a case-control study. To determine double contour (DC) sign and tophi at each site, ultrasonography (US) was performed on 10 joints for each patient (metatarsophalangeal [MTP] joints 1-2, knees, metacarpophalangeal [MCP] joints 2-3).
Five hundred-thirty joints in gouty patients and 500 joints in controls were assessed. Before study inclusion, gouty patients had a mean delay of 9.2 ± 10.7 years between first acute attack and US assessment and a mean of 14.7 ± 19.8 acute attacks. Tophi were revealed in 44% of patients during clinical exam. Mean urate level was 656.7 ± 145.3 mcmol/L. DC signs and tophi had excellent inter-reader agreement between two sonographers for all articular sites.
Frequency of DC signs in MTPs, knees and MCPs for gouty patients compared with controls was 67% vs. 2%, 56% vs. 0% and 21% vs. 0%, respectively (all P<.001). Seventy-seven percent of gouty patients had at least one articular site where a DC sign was found.Frequency of US tophi in MTPs, knees and MCPs was 42%, 74% and 23%, respectively, for gouty patients, and not found in controls (all P<.001).US found tophi in at least one articular site in 79% of gouty patients. MTPs had 67% DC sign sensitivity of US, with 57% for knees and 21% for MCPs; with high (>98%) specificity for all. In the same sites, tophi sensitivity was 74%, 42% and 23%, respectively, with 100% specificity for all sites.The DC sign, but not the tophi, was significant for uricemia (P<.05) and disease duration (P=.01) in MTPs.
“US appears a fairly inexpensive tool with good diagnosis value in gout,” the researchers concluded. “DC sign and tophi seen by US are highly specific to gout. US could help clinicians decide on [urate-lowering therapy] in early gout and when [therapy] is no longer necessary.”