Gout: New Classification Criteria from ACR/EULAR Save

The American College of Rheumatology and the European League against Rheumatism joined forces to finalize classification criteria for gout, a condition that affects 8.3 million Americans.

An expert panel of 20 investigators conducted a review of the literature on the diagnosis of gout – including new information on advanced imaging, monosodium urate (MSU) crystals identification (the gold standard) – and did a ranking exercise of 30 paper patient cases to develop preliminary criteria. These data formed the basis for developing the final classification criteria, which were also independently tested. (Citation source: http://buff.ly/1grdnoI)

The new criteria require the occurrence of at least 1 episode of peripheral joint or bursal swelling, pain, or tenderness. The presence of MSU crystals in a symptomatic joint/bursa (i.e., synovial fluid) or in a tophus is a sufficient classification of the subject as having gout, and does not require further scoring.

The domains of the new classification criteria also include:

• Clinical pattern of joint/bursa involvement (1 point for ankle or midfoot or 2 points for MTP1)
• Symptom characteristics (erythema 1 point, can’t bear to touch it 2 points, difficulty walking 3 points)
• Time course of symptomatic episodes (1 episode = 1 point; 2 or more = 2 points)
• Tophus (4 points)
• Laboratory evidence (SUA 6-8mg/dl 2 points; 8-10mg/dl 3 points; >10 mg/dl 4 points)
• Imaging evidence (double-contour sign on ultrasound or urate on DECT scan, radiographic gout-related erosion).

The maximum possible score in the final criteria is 23. A threshold score of ≥8 classifies an individual as having gout. The sensitivity and specificity of the criteria are high (92% and 89%, respectively).

Interestingly, there are negative characteristics which would take away points and lessen the odds of gout as a diagnosis. This includes if crystal analysis for MSU is negative (2 points are subtracted from the total score) or if the serum urate level is <4 mg/dl (4 points are subtracted).