Gout Classification Calculator (2015 ACR/EULAR)

Entry Criterion Must be met before applying the scoring criteria

At least one episode of swelling, pain, or tenderness in a peripheral joint or bursa?

Symptomatic episodes are periods of symptoms including any of swelling, pain, or tenderness in a peripheral joint or bursa. This is required before any further criteria apply.

MSU crystals identified in a symptomatic joint, bursa, or tophus?

Presence of monosodium urate (MSU) crystals in synovial fluid by polarizing microscopy, or in a tophus by any method. If present, the patient classifies as gout immediately - scoring domains below are not required.

Scored Domains Apply when MSU crystals not confirmed. Score ≥8 required for classification as gout.

Clinical Domains

Pattern of Joint / Bursa Involvement

0 / 2 pts

Based on symptomatic episode(s) ever. Score reflects joint involvement during any prior or current flare. First MTP (big toe) involvement scores highest.

1st MTP joint involved First metatarsophalangeal joint as part of a monoarticular or oligoarticular episode

Ankle OR midfoot involved Ankle or midfoot as part of a monoarticular or oligoarticular episode without 1st MTP involvement

Other joint(s) or bursa(e) Joints other than ankle, midfoot, or 1st MTP - or involvement only as part of polyarticular presentation

Characteristics of Symptomatic Episode(s)

0 / 3 pts

Count how many of these three features have been present during any symptomatic episode, ever. Each feature adds 1 point (up to 3 total).

Check all that apply (ever, any episode):

Erythema overlying affected joint Patient-reported or physician-observed redness over the joint during a flare

Can't bear touch or pressure to affected joint Extreme tenderness - unable to tolerate any contact with the joint

Great difficulty walking or using the joint Significant functional impairment - near inability to bear weight or use the affected joint

Time-Course of Episode(s)

0 / 2 pts

A "typical episode" requires ≥2 of these three features, regardless of anti-inflammatory treatment: (i) time to maximal pain <24 hours, (ii) resolution of symptoms in ≤14 days, (iii) complete resolution between episodes.

Recurrent typical episodes ≥2 typical episodes ever (each meeting ≥2 of the three time-course features)

One typical episode Single episode meeting ≥2 of the three time-course features

No typical episodes Atypical course or insufficient history

Clinical Evidence of Tophus

0 / 4 pts

A tophus is a draining or chalk-like subcutaneous nodule under transparent skin, often with overlying vascularity. Typical locations: joints, ears, olecranon bursae, finger pads, tendons (e.g., Achilles).

Tophus present Clinical evidence of tophus on examination at a typical location

Absent No clinical evidence of tophus

Laboratory

Serum Urate Level

0 pts

Measured by uricase method. Ideally scored during the intercritical period - when the patient is not taking urate-lowering therapy and >4 weeks from the start of an episode. The highest value ever should be scored. Note: values <4 mg/dL subtract 4 points.

≥10 mg/dL (≥0.60 mmol/L)

8 to <10 mg/dL (0.48 to <0.60 mmol/L)

6 to <8 mg/dL (0.36 to <0.48 mmol/L)

4 to <6 mg/dL (0.24 to <0.36 mmol/L) Normal range - scores 0

<4 mg/dL (<0.24 mmol/L) Very low urate - subtracts 4 points

-4

Not tested / unknown

Synovial Fluid Analysis

0 pts

Polarizing microscopy of synovial fluid from a symptomatic (ever) joint or bursa, assessed by a trained examiner. If fluid was not assessed, score as 0. MSU-negative fluid subtracts 2 points.

MSU crystals not identified (negative) Trained examiner assessed synovial fluid by polarizing microscopy - MSU crystals absent

-2

Not done / not assessed Synovial fluid analysis not performed

Imaging

Imaging Evidence of Urate Deposition

0 / 4 pts

Ultrasound: double-contour sign (hyperechoic irregular enhancement over hyaline cartilage surface, independent of insonation angle). OR DECT: color-coded urate at articular or peri-articular sites. If imaging not available, score 0.

Present (ultrasound double-contour sign OR positive DECT) Evidence of urate deposition in a symptomatic joint or bursa by either modality

Absent OR not done No qualifying finding or imaging not performed

Imaging Evidence of Gout-Related Joint Damage

0 / 4 pts

Conventional radiography (plain X-ray) of the hands and/or feet showing at least one erosion. Erosion defined as a cortical break with sclerotic margin and overhanging edge - excluding DIP joints and gull-wing appearance.

Erosion present on plain X-ray Cortical break with sclerotic margin and overhanging edge on hand/foot radiograph

Absent OR not done No qualifying erosion or X-ray not performed

Scoring summary (Step 3 domains)

Domain	Options	Score
A. Joint pattern	MTP1 / ankle-midfoot / other	0, +1, +2
B. Episode characteristics	Count of 3 features (erythema, touch, walking)	0 to +3
C. Time-course	No / one / recurrent typical episodes	0, +1, +2
D. Tophus	Absent / present	0, +4
E. Serum urate	<4 / 4-6 / 6-8 / 8-10 / ≥10 mg/dL	-4, 0, +2, +3, +4
F. Synovial fluid	Not done / MSU negative	0, -2
G. Imaging - urate	Double contour sign or DECT	0, +4
H. Imaging - erosion	Radiographic erosion (hands/feet)	0, +4
Threshold for classification		≥8

Gout Classification Calculator

Pattern of Joint / Bursa Involvement

Characteristics of Symptomatic Episode(s)

Time-Course of Episode(s)

Clinical Evidence of Tophus

Serum Urate Level

Synovial Fluid Analysis

Imaging Evidence of Urate Deposition

Imaging Evidence of Gout-Related Joint Damage

Frequently Asked Questions

Domain Breakdown