The ACR/EULAR gout classification criteria*
| Categories | Score | |
|---|---|---|
| Step 1: Entry criterion (only apply criteria below to those meeting this entry criterion) | At least 1 episode of swelling, pain, or tenderness in a peripheral joint or bursa | |
| Step 2: Sufficient criterion (if met, can classify as gout without applying criteria below) | Presence of MSU crystals in a symptomatic joint or bursa (ie, in synovial fluid) or tophus | |
| Step 3: Criteria (to be used if sufficient criterion not met) | ||
| Clinical | ||
| Pattern of joint/bursa involvement during symptomatic episode(s) ever | Ankle or mid-foot (as part of monoarticular or oligoarticular episode without involvement of the first metatarsophalangeal joint | 1 |
| Involvement of the first metatarsophalangeal joint (as part of monoarticular or oligoarticular episode) | 2 | |
| Characteristics of symptomatic episode(s) ever ▸ Erythema overlying affected joint (patient-reported or physician-observed) ▸ Can't bear touch or pressure to affected joint ▸ Great difficulty with walking or inability to use affected joint |
One characteristic Two characteristics Three characteristics |
1 2 3 |
| Time course of episode(s) ever Presence (ever) of ≥2, irrespective of anti-inflammatory treatment: ▸ Time to maximal pain <24 h ▸ Resolution of symptoms in ≤14 days ▸ Complete resolution (to baseline level) between symptomatic episodes |
One typical episode Recurrent typical episodes |
1 2 |
| Clinical evidence of tophus Draining or chalk-like subcutaneous nodule under transparent skin, often with overlying vascularity, located in typical locations: joints, ears, olecranon bursae, finger pads, tendons (eg, Achilles) | Present | 4 |
| Laboratory | ||
| Serum urate: Measured by the uricase method. Ideally should be scored at a time when the patient was not receiving urate-lowering treatment and it was >4 weeks from the start of an episode (ie, during the intercritical period); if practicable, retest under those conditions. The highest value irrespective of timing should be scored | <4 mg/dL (<0.24 mmol/L)† 6–<8 mg/dL (0.36–<0.48 mmol/L) 8–<10 mg/dL (0.48–<0.60 mmol/L) ≥10 mg/dL (≥0.60 mmol/L) | −4 2 3 4 |
| Synovial fluid analysis of a symptomatic (ever) joint or bursa (should be assessed by a trained observer)‡ | MSU negative | −2 |
| Imaging§ | ||
| Imaging evidence of urate deposition in symptomatic (ever) joint or bursa: ultrasound evidence of double-contour sign¶ or DECT demonstrating urate deposition** | Present (either modality) | 4 |
| Imaging evidence of gout-related joint damage: conventional radiography of the hands and/or feet demonstrates at least 1 erosion†† | Present | 4 |
*A web-based calculator can be accessed at: http://goutclassificationcalculator.auckland.ac.nz, and through the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) web sites.
†Symptomatic episodes are periods of symptoms that include any swelling, pain, and/or tenderness in a peripheral joint or bursa.
‡If serum urate level is <4 mg/dL (<0.24 mmoles/liter), subtract 4 points; if serum urate level is ≥4 mg/dL – >6 mg/dL (≥0.24 – <0.36 mmoles/liter), score this item as 0.
§If polarizing microscopy of synovial fluid from a symptomatic (ever) joint or bursa by a trained examiner fails to show monosodium urate monohydrate (MSU) crystals, subtract 2 points. If synovial fluid was not assessed, score this item as 0.
¶If imaging is not available, score these items as 0. #Hyperechoic irregular enhancement over the surface of the hyaline cartilage that is independent of the insonation angle of the ultrasound beam (note: false-positive double-contour sign [artifact] may appear at the cartilage surface but should disappear with a change in the insonation angle of the probe).31 ,32
**Presence of color-coded urate at articular or periarticular sites. Images should be acquired using a dual-energy computed tomography (DECT) scanner, with data acquired at 80 kV and 140 kV and analyzed using gout-specific software with a 2-material decomposition algorithm that color-codes urate.33 A positive scan is defined as the presence of color-coded urate at articular or periarticular sites. Nailbed, submillimeter, skin, motion, beam hardening, and vascular artifacts should not be interpreted as DECT evidence of urate deposition.34
††Erosion is defined as a cortical break with sclerotic margin and overhanging edge, excluding distal interphalangeal joints and gull wing appearance.