🦶 Gout Diagnosis Calculator
Apply the seven-point clinical rule to stratify patients with acute monoarthritis into low, intermediate, or high probability of gout.
Patient is male
Previous patient-reported arthritis attack
Onset within one day
Joint redness observed
First metatarsophalangeal (MTP) joint involved
Hypertension or cardiovascular disease
Serum uric acid
Add a lab value if available; > 5.88 mg/dL (0.35 mmol/L) adds to the score.
Scoring per Janssens et al. (Arthritis & Rheumatism 2010). High scores reduce the need for diagnostic arthrocentesis.
How to Use This Calculator
Assess the attack history
Gather information about prior attacks, speed of onset, and joint redness during the current flare.
Document joint involvement and comorbidities
Note first MTP involvement, hypertension/cardiovascular disease, and obtain a serum uric acid level if possible.
Calculate and interpret
Use the score to determine whether to proceed with aspiration or can initiate gout management while awaiting confirmation.
Formula
The Janssens clinical rule assigns points as follows:
- Male sex: +2.0
- Previous patient-reported arthritis attack: +2.0
- Onset within one day: +0.5
- Joint redness observed: +1.0
- First MTP involvement: +2.5
- Hypertension or cardiovascular disease: +1.5
- Serum uric acid > 5.88 mg/dL (0.35 mmol/L): +3.5
Interpretation: ≤4 low probability, 4.5-7.5 intermediate, ≥8 high probability of gout.
Full Description
Gout results from deposition of monosodium urate crystals in joints, causing acute inflammatory arthritis. While synovial fluid crystal analysis is definitive, it may not always be feasible in primary care. The Janssens rule helps identify patients likely to have gout when presenting with monoarthritis of the foot or ankle.
The rule has been validated in primary care cohorts, showing good sensitivity and specificity. It should be applied to adults with acute monoarthritis when septic arthritis has been considered. Imaging techniques such as ultrasound double contour sign or dual-energy CT can provide additional confirmation.
Use this tool to guide the urgency of rheumatology referral, need for aspiration, and early initiation of urate-lowering therapy after acute management, especially in patients with comorbid metabolic syndrome or chronic kidney disease.
Frequently Asked Questions
Can I apply the score to women?
Yes. Female sex simply scores zero for the male item. Postmenopausal women can develop gout; evaluate with the full rule and consider aspiration when in doubt.
What if uric acid is normal during an attack?
Serum uric acid may fall during acute inflammation. A normal value does not exclude gout. In that scenario the score omits the uric acid points, potentially shifting to intermediate probability—follow up with aspiration or imaging.
Does diuretic use affect the score?
Diuretics increase gout risk but are captured indirectly via hypertension/cardiovascular disease. Document medication history when deciding on urate-lowering therapy.
Is the score valid in polyarticular attacks?
The rule was derived for acute monoarthritis. For polyarticular presentations, use clinical judgment, crystal confirmation, and consider other diagnoses.
Should I still perform arthrocentesis?
Yes when infection is suspected, diagnosis remains uncertain, or the score is intermediate. Crystal analysis is definitive and guides long-term management.