The GOUT-36 prediction rule for inpatient gout flare in people with comorbid gout: derivation and external validation.

OBJECTIVES: To develop and validate a gout flare risk stratification tool for people with gout hospitalized for non-gout conditions. METHODS: The prediction rule for inpatient gout flare was derived from a cohort of 625 hospitalized people with comorbid gout from New Zealand. The rule had four items: no pre-admission gout flare prophylaxis, no pre-admission urate-lowering therapy, tophus and pre-admission serum urate >0.36 mmol/l within the previous year (GOUT-36 rule). Two or more items are required for the classification of high risk for developing inpatient gout flares. The GOUT-36 rule was validated in a prospective cohort of 284 hospitalized people with comorbid gout from Thailand and China. RESULTS: The GOUT-36 rule had a sensitivity of 75%, specificity of 67% and area under the curve of 0.71 for classifying people at high risk for developing inpatient gout flares. Four risk groups were developed: low (no items), moderate (one item), high (two items) and very high risk (three or four items). In a population with frequent (overall 34%) in-hospital gout flares, 80% of people with very high risk developed inpatient flares while 11% with low risk had inpatient flares. CONCLUSION: The GOUT-36 rule is simple and sensitive for classifying people with high risk for inpatient gout flares. The rule may help inform clinical decisions and future research on the prevention of inpatient gout flares.

Economic analysis of the 'Take Charge' intervention for people following stroke: Results from a randomised trial.

OBJECTIVE: To undertake an economic analysis of the Take Charge intervention as part of the Taking Charge after Stroke (TaCAS) study. DESIGN: An open, parallel-group, randomised trial comparing active and control interventions with blinded outcome assessment. SETTING: Community. PARTICIPANTS: Adults (n = 400) discharged to community, non-institutional living following acute stroke. INTERVENTIONS: The Take Charge intervention, a strengths based, self-directed rehabilitation intervention, in two doses (one or two sessions), and a control intervention (no Take Charge sessions). MEASURES: The cost per quality-adjusted life year (QALY) saved for the period between randomisation (always post hospital discharge) and 12 months following acute stroke. QALYs were calculated from the EuroQol-5D-5L. Costs of stroke-related and non-health care were obtained by questionnaire, hospital records and the New Zealand Ministry of Health. RESULTS: One-year post hospital discharge cost of care was mean (95% CI) $US4706 (3758-6014) for the Take Charge intervention group and $6118 (4350-8005) for control, mean (95% CI) difference $ -1412 (-3553 to +729). Health utility scores were mean (95% CI) 0.75 (0.73-0.77) for Take Charge and 0.71 (0.67-0.75) for control, mean (95% CI) difference 0.04 (0.0-0.08). Cost per QALY gained for the Take Charge intervention was $US -35,296 (=£ -25,524, € -30,019). Sensitivity analyses confirm Take Charge is cost-effective, even at a very low willingness-to-pay threshold. With a threshold of $US5000 per QALY, the probability that Take Charge is cost-effective is 99%. CONCLUSION: Take Charge is cost-effective and probably cost saving.

The effect of the Take Charge intervention on mood, motivation, activation and risk factor management: Analysis of secondary data from the Taking Charge after Stroke (TaCAS) trial.

OBJECTIVE: To use secondary data from the Taking Charge after Stroke study to explore mechanisms for the positive effect of the Take Charge intervention on physical health, advanced activities of daily living and independence for people after acute stroke. DESIGN: An open, parallel-group, randomised trial with two active and one control intervention and blinded outcome assessment. SETTING: Community. PARTICIPANTS: Adults (n = 400) discharged to community, non-institutional living following acute stroke. INTERVENTIONS: One, two, or zero sessions of the Take Charge intervention, a self-directed rehabilitation intervention which helps a person with stroke take charge of their own recovery. MEASURES: Twelve months after stroke: Mood (Patient Health Questionnaire-2, Mental Component Summary of the Short Form 36); 'ability to Take Charge' using a novel measure, the Autonomy-Mastery-Purpose-Connectedness (AMP-C) score; activation (Patient Activation Measure); body mass index (BMI), blood pressure (BP) and medication adherence (Medication Adherence Questionnaire). RESULTS: Follow-up was near-complete (388/390 (99.5%)) of survivors at 12 months. Mean age (SD) was 72.0 (12.5) years. There were no significant differences in mood, activation, 'ability to Take Charge', medication adherence, BMI or BP by randomised group at 12 months. There was a significant positive association between baseline AMP-C scores and 12-month outcome for control participants (1.73 (95%CI 0.90 to 2.56)) but not for the Take Charge groups combined (0.34 (95%CI -0.17 to 0.85)). CONCLUSION: The mechanism by which Take Charge is effective remains uncertain. However, our findings support a hypothesis that baseline variability in motivation, mastery and connectedness may be modified by the Take Charge intervention.

Development of a prediction model for inpatient gout flares in people with comorbid gout.

OBJECTIVES: Hospitalisation is a risk factor for flares in people with gout. However, the predictors of inpatient gout flare are not well understood. The aim of this study was to develop a prediction model for inpatient gout flare among people with comorbid gout. METHODS: We used data from a retrospective cohort of hospitalised patients with comorbid gout from Wellington, Aotearoa/New Zealand, in 2017 calendar year. For the development of a prediction model, we took three approaches: (A) a clinical knowledge-driven model, (B) a statistics-driven model and (C) a decision tree model. The final model was chosen based on practicality and performance, then validated using bootstrap procedure. RESULTS: The cohort consisted of 625 hospitalised patients with comorbid gout, 87 of whom experienced inpatient gout flare. Model A yielded 9 predictors of inpatient gout flare, while model B and C produced 15 and 5, respectively. Model A was chosen for its simplicity and superior C-statistics (0.82) and calibration slope (0.93). The final nine-item set of predictors were pre-admission urate >0.36 mmol/L, tophus, no pre-admission urate-lowering therapy (ULT), no pre-admission gout prophylaxis, acute kidney injury, surgery, initiation or increase of gout prophylaxis, adjustment of ULT and diuretics prior to flare. Bootstrap validation of the final model showed adequate C-statistics and calibration slope (0.80 and 0.78, respectively). CONCLUSION: We propose a set of nine predictors of inpatient flare for people with comorbid gout. The predictors are simple, practical and are supported by existing clinical knowledge.

Early development of the Australia and New Zealand Musculoskeletal Clinical Trials Network.

The Australia and New Zealand Musculoskeletal (ANZMUSC) Clinical Trials Network was formed to build capacity and infrastructure for high-quality musculoskeletal clinical trials in our region. The purpose of this paper is to describe the steps taken in its formation to help others interested in establishing similar networks. In particular, we describe the steps taken to form the collaboration and our progress in achieving our vision and mission. Our aim is to focus on trials of highest importance and quality to provide definitive answers to the most pressing questions in our field.

Gout, Hyperuricaemia and Crystal-Associated Disease Network (G-CAN) consensus statement regarding labels and definitions of disease states of gout.

OBJECTIVE: There is a lack of standardisation in the terminology used to describe gout. The aim of this project was to develop a consensus statement describing the recommended nomenclature for disease states of gout. METHODS: A content analysis of gout-related articles from rheumatology and general internal medicine journals published over a 5-year period identified potential disease states and the labels commonly assigned to them. Based on these findings, experts in gout were invited to participate in a Delphi exercise and face-to-face consensus meeting to reach agreement on disease state labels and definitions. RESULTS: The content analysis identified 13 unique disease states and a total of 63 unique labels. The Delphi exercise (n=76 respondents) and face-to-face meeting (n=35 attendees) established consensus agreement for eight disease state labels and definitions. The agreed labels were as follows: 'asymptomatic hyperuricaemia', 'asymptomatic monosodium urate crystal deposition', 'asymptomatic hyperuricaemia with monosodium urate crystal deposition', 'gout', 'tophaceous gout', 'erosive gout', 'first gout flare' and 'recurrent gout flares'. There was consensus agreement that the label 'gout' should be restricted to current or prior clinically evident disease caused by monosodium urate crystal deposition (gout flare, chronic gouty arthritis or subcutaneous tophus). CONCLUSION: Consensus agreement has been established for the labels and definitions of eight gout disease states, including 'gout' itself. The Gout, Hyperuricaemia and Crystal-Associated Disease Network recommends the use of these labels when describing disease states of gout in research and clinical practice.

Relationship between serum urate concentration and clinically evident incident gout: an individual participant data analysis.

OBJECTIVES: To provide estimates of the cumulative incidence of gout according to baseline serum urate. METHODS: Using individual participant data from four publicly available cohorts (Atherosclerosis Risk in Communities Study, Coronary Artery Risk Development in Young Adults Study, and both the Original and Offspring cohorts of the Framingham Heart Study), the cumulative incidence of clinically evident gout was calculated according to baseline serum urate category. Cox proportional hazards modelling was used to evaluate the relation of baseline urate categories to risk of incident gout. RESULTS: This analysis included 18 889 participants who were gout-free at baseline, with mean (SD) 11.2 (4.2) years and 212 363 total patient-years of follow-up. The cumulative incidence at each time point varied according to baseline serum urate concentrations, with 15-year cumulative incidence (95% CI) ranging from 1.1% (0.9 to 1.4) for <6 mg/dL to 49% (31 to 67) for ≥10 mg/dL. Compared with baseline serum urate <6 mg/dL, the adjusted HR for baseline serum urate 6.0-6.9 mg/dL was 2.7, for 7.0-7.9 mg/dL was 6.6, for 8.0-8.9 mg/dL was 15, for 9.0-9.9 mg/dL was 30, and for ≥10 mg/dL was 64. CONCLUSIONS: Serum urate level is a strong non-linear concentration-dependent predictor of incident gout. Nonetheless, only about half of those with serum urate concentrations ≥10mg/dL develop clinically evident gout over 15 years, implying a role for prolonged hyperuricaemia and additional factors in the pathogenesis of gout.

Rasch analysis suggests that health assessment questionnaire II is a generic measure of physical functioning for rheumatic diseases: a cross-sectional study.

BACKGROUND: Versions of the Health Assessment Questionnaire (HAQ) are commonly used to measure physical functioning across multiple rheumatic diseases but there has been no clear demonstration that any HAQ version is actually generic. This study aimed to show that the HAQ-II instrument is invariant across different rheumatic disease categories using the Rasch measurement model, which would confirm that the instrument is generic. METHODS: HAQ-II responses from 882 consecutive rheumatology clinic attendees were fitted to a Rasch model. Invariance across disease was assessed by analysis of variance of residuals implemented in RUMM2030. Rasch modeled HAQ-II scores across disease categories were compared and the mathematical relationship between raw HAQ-II scores and Rasch modeled scores was also determined. RESULTS: The HAQ-II responses fitted the Rasch model. There was no substantive evidence for lack of invariance by disease category except for a single item ("opening car doors"). Rasch modeled scores could be accurately obtained from raw scores with a cubic formula (R2 0.99). Patients with rheumatoid arthritis had more disability than patients with other kinds of inflammatory arthritis or autoimmune connective tissue disease. CONCLUSIONS: The HAQ-II can be used across different rheumatic diseases and scores can be similarly interpreted from patients with different diseases. Transforming raw scores to Rasch modeled scores enable a strictly linear, interval scale to be used. It remains to be seen how that would affect interpretation of change scores. TRIAL REGISTRATION: ANZCTR ACTRN12617001500347 . Registered 24th October 2017 (retrospectively registered).

Weight loss for overweight and obese individuals with gout: a systematic review of longitudinal studies.

OBJECTIVES: Weight loss is commonly recommended for gout, but the magnitude of the effect has not been evaluated in a systematic review. The aim of this systematic review was to determine benefits and harms associated with weight loss in overweight and obese patients with gout. METHODS: We searched six databases for longitudinal studies, reporting the effect of weight loss in overweight/obese gout patients. Risk of bias was assessed using the tool Risk of Bias in Non-Randomised Studies of Interventions. The quality of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation. RESULTS: From 3991 potentially eligible studies, 10 were included (including one randomised trial). Interventions included diet with/without physical activity, bariatric surgery, diuretics, metformin or no intervention. Mean weight losses ranged from 3 kg to 34 kg. Clinical heterogeneity in study characteristics precluded meta-analysis. The effect on serum uric acid (sUA) ranged from -168 to 30 µmol/L, and 0%-60% patients achieving sUA target (<360 µmol/L). Six out of eight studies (75%) showed beneficial effects on gout attacks. Two studies indicated dose-response relationship for sUA, achieving sUA target and gout attacks. At short term, temporary increased sUA and gout attacks tended to occur after bariatric surgery. CONCLUSIONS: The available evidence is in favour of weight loss for overweight/obese gout patients, with low, moderate and low quality of evidence for effects on sUA, achieving sUA target and gout attacks, respectively. At short term, unfavourable effects may occur. Since the current evidence consists of a few studies (mostly observational) of low methodological quality, there is an urgent need to initiate rigorous prospective studies (preferably randomised controlled trials). SYSTEMATIC REVIEW REGISTRATION: PROSPERO, CRD42016037937.

Performance of the 2015 ACR-EULAR classification criteria for gout in a primary care population presenting with monoarthritis.

Objective: To test the performance of the 2015 ACR-EULAR gout classification criteria against presence of SF MSU crystals in a primary healthcare population. Methods: The criteria were applied to an existing dataset of consecutive patients with monoarthritis presenting to Dutch family physicians; all patients underwent microscopic SF analysis by design. The data had been prospectively collected to develop a diagnostic decision rule for gout in 2010. Diagnostic performance was assessed by calculating area under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and constructing calibration plots for the full version of the criteria (including SF analysis results of all patients) and the clinical-only version (not including SF analysis results). Performance of both versions was compared with the 2010 diagnostic rule. Results: Of 381 patients enrolled into the study, 216 (57%) were MSU crystal-positive. The full and clinical-only versions of the criteria had satisfactory area under the receiver operating characteristic curve (0.96 and 0.87, respectively), high specificity (0.98 and 0.84), high PPV (0.98 and 0.84), but lower sensitivity (0.68 and 0.68) and NPV (0.70 and 0.67). Specificity and PPV of both versions were higher compared with 0.71 and 0.89 of the 2010 diagnostic decision rule. The decison rule had the highest sensitivity and NPV (0.99 and 0.97). Conclusion: This study presents the first external validation of the 2015 ACR-EULAR gout classification criteria in a primary healthcare setting. The criteria perform well in this setting in patients presenting with monoarthritis for the purpose of enrolling into gout clinical trials.

Pros and cons of conjoint analysis of discrete choice experiments to define classification and response criteria in rheumatology.

PURPOSE OF REVIEW: Conjoint analysis of choice or preference data has been used in marketing for over 40 years but has appeared in healthcare settings much more recently. It may be a useful technique for applications within the rheumatology field. RECENT FINDINGS: Conjoint analysis in rheumatology contexts has mainly used the approaches implemented in 1000Minds Ltd, Dunedin, New Zealand, Sawtooth Software, Orem UT, USA. Examples include classification criteria, composite response criteria, service prioritization tools and utilities assessment. Limitations imposed by very many attributes can be managed using new techniques. Conjoint analysis studies of classification and response criteria suggest that the assumption of equal weighting of attributes cannot be met, which challenges traditional approaches to composite criteria construction. Weights elicited through choice experiments with experts can derive more accurate classification criteria, than unweighted criteria. Studies that find significant variation in attribute weights for composite response criteria for gout make construction of such criteria problematic. SUMMARY: Better understanding of various multiattribute phenomena is likely to increase with increased use of conjoint analysis, especially when the attributes concern individual perceptions or opinions. In addition to classification criteria, some applications for conjoint analysis that are emerging in rheumatology include prioritization tools, remission criteria, and utilities for life areas.

Factors associated with change in radiographic damage scores in gout: a prospective observational study.

BACKGROUND/AIMS: Radiographic damage is frequently observed in patients with longstanding gout. The aim of this prospective observational study was to determine factors associated with change in radiographic damage scores in gout. METHODS: People with gout and disease duration <10 years were recruited into this prospective observational study. At the baseline visit, structured assessment was undertaken in 290 participants including detailed clinical examination and plain radiographs (XR) of the hands and feet. Participants were invited to attend a further study visit with repeat XR 3 years after the baseline visit. XR were scored for erosion and joint space narrowing according to the gout-modified Sharp/van der Heijde XR damage score. RESULTS: Age, subcutaneous tophus count and tender joint count were independently associated with XR damage score at the baseline visit. Paired serial XR were available for 140 participants. In stepwise linear regression analysis, change in total damage score over 3 years was positively associated with change in subcutaneous tophus count and baseline XR damage score, and inversely associated with baseline subcutaneous tophus count (model R2=0.39, p<0.001). Change in subcutaneous tophus count contributed most to the change in erosion score (partial R2 change=0.31, p<0.001), and baseline XR damage score contributed most to the change in narrowing score (partial R2 change=0.31, p<0.001). CONCLUSIONS: Development of new subcutaneous tophi and baseline radiographic damage are associated with progressive joint damage scores in people with gout. These data provide further evidence that the tophus plays a central role in bone erosion in gout.

Performance of classification criteria for gout in early and established disease.

OBJECTIVES: To compare the sensitivity and specificity of different classification criteria for gout in early and established disease. METHODS: This was a cross-sectional study of consecutive rheumatology clinic patients with joint swelling in which gout was defined by presence or absence of monosodium urate crystals as observed by a certified examiner at presentation. Early disease was defined as patient-reported onset of symptoms of 2 years or less. RESULTS: Data from 983 patients were collected and gout was present in 509 (52%). Early disease was present in 144 gout cases and 228 non-cases. Sensitivity across criteria was better in established disease (95.3% vs 84.1%, p<0.001) and specificity was better in early disease (79.9% vs 52.5%, p<0.001). The overall best performing clinical criteria were the Rome criteria with sensitivity/specificity in early and established disease of 60.3%/84.4% and 86.4%/63.6%. Criteria not requiring synovial fluid analysis had sensitivity and specificity of less than 80% in early and established disease. CONCLUSIONS: Existing classification criteria for gout have sensitivity of over 80% in early and established disease but currently available criteria that do not require synovial fluid analysis have inadequate specificity especially later in the disease. Classification criteria for gout with better specificity are required, although the findings should be cautiously applied to non-rheumatology clinic populations.

Which aspects of health are most important for patients with spondyloarthritis? A Best Worst Scaling based on the ASAS Health Index.

OBJECTIVE: The aim was to investigate the importance of aspects of health for patients with axial SpA (axSpA) and to explore differences across different subgroups. METHODS: A Best Worst Scaling exercise was conducted in patients with axSpA from 20 countries (10 patients per country) worldwide. Using the 17 items of the Assessment of SpondyloArthritis international Society Health Index, a set of 17 choice tasks was generated. Patients had to indicate in each choice task the most and least important out of four varying items. The hierarchical Bayes method was used to estimate the relative importance score for each item (summing to 100). Subgroup comparisons were performed for relevant demographic (gender, age, work status, geographical area and education) and disease characteristics (SpA phenotype, disease duration and disease activity) using one-way analysis of variance or the Mann-Whitney U-test. RESULTS: The experiment was completed by 199 patients with axSpA [117 (58.8%) men, mean (sd) age 42.3 (13.6) years, mean (sd) disease duration 11.1 (11.2) years, 130 (65.3%) AS]. The highest relative importance was assigned to pain (14.2; 95% CI: 13.8, 14.6), sleep (10.3; 95% CI: 9.6, 11.0), being exhausted (9.6; 95% CI: 9.0, 10.3), standing (9.25; 95% CI: 8.5, 10.0) and motivation to do anything that requires physical effort (8.7; 95% CI: 8.1, 9.3). The lowest relative importance was assigned to sexual relationships, toileting, contact with people, driving and washing hair. Differences between subgroups were small or in aspects with lower importance. CONCLUSION: A clear gradient was seen in the importance of the different aspects of health that impact functioning of patients with axSpA. Differences between subgroups were small or non-existent. These findings help to align clinical care to patients' needs.

Gout Classification Criteria: Update and Implications.

Gout is the most common inflammatory arthritis, with a rising prevalence and incidence worldwide. There has been a resurgence in gout research, fueled, in part, by a number of advances in pharmacologic therapy for gout. The conduct of clinical trials and other observational research in gout requires a standardized and validated means of assembling well-defined groups of patients with gout for such research purposes. Recently, an international collaborative effort that involved a data-driven process with state-of-the art methodology supported by the American College of Rheumatology and the European League Against Rheumatism led to publication of new gout classification criteria.

Measuring Neurobehavioral Functioning in People With Traumatic Brain Injury: Rasch Analysis of Neurobehavioral Functioning Inventory.

OBJECTIVE: To examine internal construct validity of the Neurobehavioral Functioning Inventory (NFI) by applying Rasch analysis. SETTING: An outpatient rehabilitation program trial in New Zealand employing a goal-setting intervention in people with traumatic brain injury (TBI). PARTICIPANTS: One hundred eight people (mean age = 46 years; 73% male) between 6 months and 5 years post-TBI. DESIGN: Rasch analysis of the NFI (Partial Credit Model). RESULTS: Three NFI subscales were not unidimensional and at least 4 items in each subscale had disordered response categories. Two items showed differential item functioning by age, 1 item by educational attainment, and 2 items were found to misfit the overall construct. These items were excluded from the total score calculation. The revised scale fit the Rasch model and supported the internal construct validity of the NFI. CONCLUSIONS: Current scoring of the NFI subscales for people with TBI in New Zealand does not meet the requirements of the Rasch model. The revised version of NFI can improve the interpretation of scores but should be further tested with people with TBI in other settings.

Imaging modalities for the classification of gout: systematic literature review and meta-analysis.

BACKGROUND: Although there has been major progress in gout imaging, no gout classification criteria currently include advanced imaging techniques. OBJECTIVE: To examine the usefulness of imaging modalities in the classification of gout when compared to monosodium urate (MSU) crystal confirmation as the gold standard, in order to inform development of new gout classification criteria. METHODS: We systematically reviewed the published literature concerning the diagnostic performance of plain film radiography, MRI, ultrasound (US), conventional CT and dual energy CT (DECT). Only studies with MSU crystal confirmation as the gold standard were included. When more than one study examined the same imaging feature, the data were pooled and summary test characteristics were calculated. RESULTS: 11 studies (9 manuscripts and 2 meeting abstracts) satisfied the inclusion criteria. All were set in secondary care, with mean gout disease duration of at least 7 years. Three features were examined in more than one study: the double contour sign (DCS) on US, tophus on US, and MSU crystal deposition on DECT. The pooled (95% CI) sensitivity and specificity of US DCS were 0.83 (0.72 to 0.91) and 0.76 (0.68 to 0.83), respectively; of US tophus, were 0.65 (0.34 to 0.87) and 0.80 (0.38 to 0.96), respectively; and of DECT, were 0.87 (0.79 to 0.93) and 0.84 (0.75 to 0.90), respectively. CONCLUSIONS: US and DECT show promise for gout classification but the few studies to date have mostly been in patients with longstanding, established disease. The contribution of imaging over clinical features for gout classification criteria requires further examination.

Development of a patient-reported outcome measure of tophus burden: the Tophus Impact Questionnaire (TIQ-20).

BACKGROUND: Tophus burden is currently measured using physical examination and imaging methods. The aim of this study was to develop a patient-reported outcome (PRO) tool to assess tophus burden in people with gout. METHODS: The responses from interviews with 25 people with tophaceous gout were used to generate items for a preliminary PRO tool. Following cognitive testing of each item, a preliminary 34-item questionnaire was administered to 103 people with tophaceous gout. Rasch analysis generated a 20-item Tophus Impact Questionnaire (TIQ-20). Test-retest reproducibility and construct validity of the TIQ-20 were assessed. RESULTS: The TIQ-20 responses fit the Rasch model and demonstrated unidimensionality, adequate precision, absence of differential item functioning and adequate person separation index. The TIQ-20 included items related to pain, activity limitation, footwear modification, participation, psychological impact and healthcare use due to tophi. In the 103 patients with tophaceous gout, floor effects were observed in 4.9% and ceiling effects in 1%. The TIQ-20 test-retest intraclass correlation coefficient was 0.76 (95% CI 0.61 to 0.85). All predicted correlations for construct validity testing were observed, including weak correlation with serum urate concentrations (r<0.30), moderate correlation with subcutaneous tophus count and dual energy CT urate volume (r=0.30-0.50), and stronger correlation with Health Assessment Questionnaire scores (r>0.50). CONCLUSIONS: We have developed a tophus-specific PRO in patients with tophaceous gout. The TIQ-20 demonstrates acceptable psychometric properties. Initial results show internal, face and construct validity, reproducibility and feasibility. Further research is required to determine responsiveness to change.

2015 Gout classification criteria: an American College of Rheumatology/European League Against Rheumatism collaborative initiative.

OBJECTIVE: Existing criteria for the classification of gout have suboptimal sensitivity and/or specificity, and were developed at a time when advanced imaging was not available. The current effort was undertaken to develop new classification criteria for gout. METHODS: An international group of investigators, supported by the American College of Rheumatology and the European League Against Rheumatism, conducted a systematic review of the literature on advanced imaging of gout, a diagnostic study in which the presence of monosodium urate monohydrate (MSU) crystals in synovial fluid or tophus was the gold standard, a ranking exercise of paper patient cases, and a multi-criterion decision analysis exercise. These data formed the basis for developing the classification criteria, which were tested in an independent data set. RESULTS: The entry criterion for the new classification criteria requires the occurrence of at least one episode of peripheral joint or bursal swelling, pain, or tenderness. The presence of MSU crystals in a symptomatic joint/bursa (ie, synovial fluid) or in a tophus is a sufficient criterion for classification of the subject as having gout, and does not require further scoring. The domains of the new classification criteria include clinical (pattern of joint/bursa involvement, characteristics and time course of symptomatic episodes), laboratory (serum urate, MSU-negative synovial fluid aspirate), and imaging (double-contour sign on ultrasound or urate on dual-energy CT, radiographic gout-related erosion). The sensitivity and specificity of the criteria are high (92% and 89%, respectively). CONCLUSIONS: The new classification criteria, developed using a data-driven and decision-analytic approach, have excellent performance characteristics and incorporate current state-of-the-art evidence regarding gout.