Can Ultrasonography Help Diagnose Gout?

Summary and Comment |
March 16, 2017

Can Ultrasonography Help Diagnose Gout?

  1. Mark Greenberg, MD and
  2. Allan S. Brett, MD

Ultrasound might be useful, but synovial fluid analysis remains the gold standard.

  1. Mark Greenberg, MD and
  2. Allan S. Brett, MD

Ultrasound is used increasingly for diagnosing gout. Three sonographic features of monosodium urate (MSU) crystal deposition are double contour sign (hyperechoic enhancement of articular surfaces), tophus (hyperechoic aggregates), and a “snowstorm” appearance (floating hyperechoic foci representing MSU aggregates). Investigators analyzed data from 824 patients with clinically suspected gout and at least one swollen joint or subcutaneous nodule who were enrolled in an international multicenter study. All patients underwent both ultrasonography and joint or nodule aspiration. Although all ultrasonographers had training, they were not required to follow a formal scanning protocol.

Half the patients had MSU crystals on joint or nodule aspiration, and half were MSU-negative. With joint aspirate as the gold standard, the sensitivity, specificity, positive predictive value, and negative predictive value of having any one ultrasound sign were 77%, 84%, 83%, and 78%, respectively. Taken separately, each of the three ultrasound signs was at least 90% specific (few false positives); however, their individual sensitivities were 60% or less (i.e., each sign was absent in many gout patients).

Comment

Synovial fluid analysis remains the preferred approach to diagnosing gout. Nevertheless, ultrasound might be helpful particularly in patients with high clinical suspicion of gout despite negative or technically difficult arthrocentesis. However, several caveats should be noted. First, positive and negative predictive values depend on prevalence of gout in a study population; these values would differ in populations with a higher or lower gout prevalence than this study's 50% prevalence. Second, ultrasound accuracy varies according to operator skill. And third, these probabilities should be integrated with other information that might affect a patient's likelihood of gout (e.g., uric acid level, history and location of previous joint inflammation episodes, and plausibility of alternative conditions such as infection).

Dr. Greenberg is an Associate Professor of Medicine in the Division of Rheumatology at the University of South Carolina School of Medicine in Columbia.

Editor Disclosures at Time of Publication

  • Disclosures for Allan S. Brett, MD at time of publication Nothing to disclose

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