Gout Diagnosis Calculator (2015 ACR/EULAR gout classification criteria)

Understanding the gout classification calculator — concept and principle

This calculator applies the 2015 ACR/EULAR gout classification criteria. It adds points for the pattern of joint attacks, their features and time course, tophi, serum urate and imaging, and shows whether the total reaches the 8 points needed to classify a person as having gout.

How it is calculated

Entry: at least one episode of swelling, pain or tenderness in a peripheral joint or bursa.

Sufficient: urate (MSU) crystals in a symptomatic joint, bursa or tophus classify gout without further scoring.

Otherwise add:

• Joint pattern: ankle or midfoot 1, big-toe base joint 2.
• Attack features (redness, cannot bear touch, hard to walk or use the joint): 1 per feature, up to 3.
• Time course: one typical attack 1, recurrent 2.
• Tophus 4.
• Serum urate: under 4 mg/dL −4, 4 to under 6 0, 6 to under 8 2, 8 to under 10 3, 10 or more 4.
• Joint fluid checked with no crystals −2; urate deposits on ultrasound or dual-energy CT 4; gout erosion on X-ray 4.

Total of 8 or more = classified as gout. µmol/L ÷ 59.48 = mg/dL.

The principle

The criteria were built by experts from a large international study of patients with and without gout, weighting each feature by how well it separated the two groups. Crystals are the gold standard, so they are sufficient on their own. Typical big-toe attacks, high urate and imaging evidence of urate deposits each add strong evidence, while a low urate or crystal-free joint fluid count against gout.

Worked example

Default inputs: entry yes, no crystals seen, big-toe joint, all three features, repeated typical attacks, no tophus, urate 8.5 mg/dL, no fluid test, no imaging findings.

1. Joint 2 + features 3 + time course 2 = 7.
2. Urate 8.5 is in 8 to under 10 → 3 points.
3. Tophus, fluid, ultrasound and X-ray add 0.
4. Total 10, needed 8 → Classified as gout.

How to read the result

Reaching 8 points means the picture matches gout well enough for research classification. Not reaching it does not exclude gout; a doctor may still diagnose it, especially early in the disease. The best confirmation is finding crystals in joint fluid.

Common mistakes

• Using a urate value measured during an attack, when it can be falsely normal.
• Using a urate value taken while on urate-lowering medicine.
• Counting attacks in non-peripheral joints such as the spine.

Frequently asked questions

Can uric acid be normal during a gout attack?

Yes. It often falls during an attack, so a repeat test about 4 weeks later is more reliable.

What is a tophus?

A chalky lump of urate crystals under the skin, often near joints, ears or tendons.

Is high uric acid alone gout?

No. Many people with high uric acid never have an attack.

Sources: Neogi T, Jansen TL, Dalbeth N, et al., "2015 Gout classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative", Arthritis Rheumatol 2015;67(10):2557–2568; Ann Rheum Dis 2015;74(10):1789–1798