Gout Diagnosis Calculator (ACR/EULAR 2015 + Acute Rule)

What is the 2015 ACR/EULAR Gout Classification Criteria?

The 2015 ACR/EULAR Gout Classification Criteria is a validated scoring system jointly developed by the American College of Rheumatology and the European League Against Rheumatism. It was published in 2015 after a large international study involving more than 1,000 patients and replaced older, less precise criteria. The system evaluates three broad domains: clinical findings (joint location, episode characteristics, time course, and tophus), laboratory results (serum urate and synovial fluid analysis), and imaging findings (ultrasound or dual-energy CT evidence of urate deposition, and X-ray evidence of joint damage). A total score of 8 or higher classifies a patient as having gout, with a sensitivity of 92% and specificity of 89% compared to the gold-standard diagnosis of MSU crystal identification in synovial fluid or tophus.

How the scoring system works

The calculator first checks two gateway conditions. The entry criterion requires that the patient has had at least one episode of swelling, pain, or tenderness in a peripheral joint or bursa - without this, the criteria cannot be applied. The sufficient criterion is met if monosodium urate crystals have been identified in synovial fluid or tophus material by polarised-light microscopy: this alone classifies the patient as having gout without further scoring. If neither gateway condition applies, the eight scoring domains are evaluated. The clinical domain contributes up to 11 points. The laboratory domain ranges from -4 (if serum urate is very low, which makes gout unlikely) to +4 for high urate, with a -2 deduction for a negative synovial fluid result. Imaging findings can each add 4 points. A score of 8 or more is the classification threshold.

The Acute Gout Diagnosis Rule (Janssens et al.)

This tool also calculates the Acute Gout Diagnosis Rule, published by Janssens and colleagues in the Annals of Internal Medicine (2010). It was developed specifically for the primary care and emergency medicine settings, where synovial fluid analysis is often not available. It uses seven simple clinical and laboratory items: male sex (+2), a previous self-reported arthritis attack (+2), symptom onset peaking within one day (+0.5), joint redness (+1), first metatarsophalangeal joint involvement (+2.5), hypertension or cardiovascular disease (+1.5), and serum uric acid above 5.88 mg/dL (+3.5). A total score of 4 or below makes gout unlikely; a score between 4 and 8 suggests joint aspiration would be most informative; and a score of 8 or above makes gouty arthritis very likely. This rule has a sensitivity of 85% and specificity of 80% for the primary care setting.

Gout: causes, risk factors, and what to do next

Gout is caused by the deposition of monosodium urate crystals in joints and soft tissues. It results from persistently elevated serum urate (hyperuricaemia), which occurs when the body produces too much uric acid, excretes too little of it (or both). Risk factors include a diet high in purine-rich foods (red meat, organ meats, shellfish), high-fructose foods, and alcohol (particularly beer); diuretic use; chronic kidney disease; obesity; hypertension; and a family history of gout. Acute attacks are managed with non-steroidal anti-inflammatory drugs, colchicine, or corticosteroids. Long-term management targets a serum urate below 6 mg/dL (below 5 mg/dL in patients with tophi or frequent attacks) using urate-lowering therapy such as allopurinol or febuxostat. Lifestyle changes - reducing purine and alcohol intake, increasing hydration, and losing excess weight - are recommended alongside medication.