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.

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.

Self-Reflective Meaning Making in Troubled Times: Change in Self-Identity After Traumatic Brain Injury

Our aim with this article is to clarify the concept of change in self-identity following traumatic brain injury (TBI). We used concept analysis methodology-predominantly concept clarification. We identified 110 articles using a systematic literature search, and used critical appraisal, content analysis, and analytical questioning to explore attributes and boundaries. A reported change in self-identity is the ultimate expression of a variety of cognitive, psychological, and social sequelae of TBI. We present an integrative model of this process, identifying three potential levels of change: (a) component parts (egocentric self, sociocentric self, and "identity as shared with others"); (b) integral processes (self-awareness and expression via meaningful occupation and narratives); and (c) whole-system disruption. Change in self-identity after TBI is a highly individualistic process. The driver of this process is "self-reflective meaning making," giving a purpose and direction in life, providing motivation and goals for future behavior.

Peripheral spondyloarthritis and psoriatic arthritis; overlaps and distinctions: a report from the GRAPPA 2012 annual meeting

For over 40 years the concept of psoriatic arthritis (PsA) has slowly evolved as new knowledge has emerged. This has been facilitated by the development of new criteria for classification, improvement on existing criteria by the use of updated methodologies, and new information about the disease. At the same time, there has been discussion about categorization within the generic term spondyloarthritis. At the 2012 annual meeting of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA), some of this history was reviewed, along with the current thinking about the taxonomy of PsA within spondyloarthritis.

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.

Establishing a person-centred framework of self-identity after traumatic brain injury: a grounded theory study to inform measure development

OBJECTIVE

To develop a theoretically sound, client-derived framework to underpin development of a measure reflecting the impact of traumatic brain injury (TBI) on a person's self-identity.

DESIGN

Grounded theory, based on transcription of audio recordings from focus group meetings with people who have experienced TBI, analysed with constant comparative methods.

SETTING

8 different urban and rural communities in New Zealand.

PARTICIPANTS

49 people (34 men, 15 women), 6 months to 36 years after mild-to-severe TBI.

RESULTS

The central concept emerging from the data was that of desiring to be or having lost a sense of being an integrated and valued person. The three main subthemes were: (1) having a coherent, satisfying and complete sense of oneself, (2) respect, validation and acceptance by others and (3) having a valued place in the world.

CONCLUSIONS

This study reinforces the notion that change in self-identity is an important aspect of life after TBI, and provides information on what this concept means to people with TBI. In order to scientifically evaluate relationships between self-identity and other aspects of health (eg, depression, quality of life), and to test the effect of interventions to address problems with self-identity after TBI, a quantitative tool for evaluation of this construct is required. Themes from this research provide a foundation for the development of a measure of self-identity grounded in the language and experience of people with TBI.

Outcome measures in acute gout: a systematic literature review

OBJECTIVE

Five core domains have been endorsed by Outcome Measures in Rheumatology (OMERACT) for acute gout: pain, joint swelling, joint tenderness, patient global assessment, and activity limitation. We evaluated instruments for these domains according to the OMERACT filter: truth, feasibility, and discrimination.

METHODS

A systematic search strategy for instruments used to measure the acute gout core domains was formulated. For each method, articles were assessed by 2 reviewers to summarize information according to the specific components of the OMERACT filter.

RESULTS

Seventy-seven articles and abstracts met the inclusion criteria. Pain was most frequently reported (76 studies, 20 instruments). The pain instruments used most often were 100 mm visual analog scale (VAS) and 5-point Likert scale. Both methods have high feasibility, face and content validity, and within- and between-group discrimination. Four-point Likert scales assessing index joint swelling and tenderness have been used in numerous acute gout studies; these instruments are feasible, with high face and content validity, and show within- and between-group discrimination. Five-point Patient Global Assessment of Response to Treatment (PGART) scales are feasible and valid, and show within- and between-group discrimination. Measures of activity limitations were infrequently reported, and insufficient data were available to make definite assessments of the instruments for this domain.

CONCLUSION

Many different instruments have been used to assess the acute gout core domains. Pain VAS and 5-point Likert scales, 4-point Likert scales of index joint swelling and tenderness and 5-point PGART instruments meet the criteria for the OMERACT filter.

Application of the OMERACT filter to measures of core outcome domains in recent clinical studies of acute gout

OBJECTIVE

To determine the extent to which instruments that measure core outcome domains in acute gout fulfill the Outcome Measures in Rheumatology (OMERACT) filter requirements of truth, discrimination, and feasibility.

METHODS

Patient-level data from 4 randomized controlled trials of agents designed to treat acute gout and 1 observational study of acute gout were analyzed. For each available measure, construct validity, test-retest reliability, within-group change using effect size, between-group change using the Kruskall-Wallis statistic, and repeated measures generalized estimating equations were assessed. Floor and ceiling effects were also assessed and minimal clinically important difference was estimated. These analyses were presented to participants at OMERACT 11 to help inform voting for possible endorsement.

RESULTS

There was evidence for construct validity and discriminative ability for 3 measures of pain [0 to 4 Likert, 0 to 10 numeric rating scale (NRS), 0 to 100 mm visual analog scale (VAS)]. Likewise, there appears to be sufficient evidence for a 4-point Likert scale to possess construct validity and discriminative ability for physician assessment of joint swelling and joint tenderness. There was some evidence for construct validity and within-group discriminative ability for the Health Assessment Questionnaire as a measure of activity limitations, but not for discrimination between groups allocated to different treatment.

CONCLUSION

There is sufficient evidence to support measures of pain (using Likert, NRS, or VAS), joint tenderness, and swelling (using Likert scale) as fulfilling the requirements of the OMERACT filter. Further research on a measure of activity limitations in acute gout clinical trials is required.

Reduced creatinine clearance is associated with early development of subcutaneous tophi in people with gout

Background

Although typically a late feature of gout, tophi may present early in the course of disease. The aim of this study was to identify factors associated with the presence of early tophaceous disease.

Methods

People with gout for <10 years were prospectively recruited, and had a comprehensive clinical assessment including examination for subcutaneous tophi. The clinical factors independently associated with the presence and number of tophi were analyzed using regression models.

Results

Of the 290 participants, there were 47 (16.2%) with clinically apparent tophi. In univariate analysis, those with tophi were older, were more frequently taking diuretics and colchicine prophylaxis, and had lower creatinine clearance. The association between the presence of tophi and creatinine clearance was strongest in those with creatinine clearance ≤30 ml/min. In logistic regression analysis, creatinine clearance ≤30 ml/min was associated with the presence of tophi, even after adjusting for ethnicity, corticosteroid use, colchicine use and diuretic use (multivariate adjusted odds ratio 7.0, p = 0.005). Participants with tophi reported higher frequency of gout flares, pain scores, patient global assessment scores, and HAQ scores.

Conclusions

The presence of tophi is associated with more symptomatic disease in people with gout for <10 years. Creatinine clearance is independently associated with early presentation of subcutaneous tophi.

OMERACT endorsement of measures of outcome for studies of acute gout

OBJECTIVE

To determine the extent to which participants at the Outcome Measures in Rheumatology (OMERACT) 11 meeting agree that instruments used in clinical trials to measure OMERACT core outcome domains in acute gout fulfill OMERACT filter requirements of truth, discrimination, and feasibility; and where future research efforts need to be directed.

METHODS

Results of a systematic literature review and analysis of individual-level data from recent clinical studies of acute gout were presented to OMERACT participants. The information was discussed in breakout groups, and opinion was defined by subsequent voting in a plenary session. Endorsement was defined as at least 70% of participants voting in agreement with the proposition (where the denominator excluded those participants who did not vote or who voted "don't know").

RESULTS

The following measures were endorsed for use in clinical trials of acute gout: (1) 5-point Likert scale and/or visual analog scale (0 to 100 mm) to measure pain; (2) 4-point Likert scale for joint swelling; (3) 4-point Likert scale for joint tenderness; and (4) 5-point Likert scale for patient global assessment of response to treatment. Measures for the activity limitations domain were not endorsed.

CONCLUSION

Measures of pain, joint swelling, joint tenderness, and patient global assessment in acute gout were endorsed at OMERACT 11. These measures should now be used in clinical trials of acute gout.

Do patient preferences for core outcome domains for chronic gout studies support the validity of composite response criteria?

OBJECTIVE

To determine patient-derived weights or prioritization for core outcome domains in chronic gout clinical studies.

METHODS

Three patient groups participated in a conjoint decision-making exercise using 1000Minds software, which asked participants to make repeated judgments regarding which of 2 hypothetical patients with gout represented the best response to treatment. Each scenario compared 2 patients on the basis of change in 2 of 5 core outcome domains at a time. Agreement of 80% of the group was required to answer each scenario. Re-voting was performed once after discussion in instances of disagreement.

RESULTS

The relative importance accorded to each outcome domain was different across the 3 groups of patients. There was some consistency that tophi was the least or second to least important outcome domain for every group and pain between attacks was ranked in the bottom third of priority for all groups. Gout attacks were ranked as the second or third most important domain in each group. However, the relative importance of serum urate (SUA) and activity limitations was quite different among the 3 groups, with 1 group ranking SUA as the most important outcome and 1 group ranking it as the second to least important outcome.

CONCLUSION

Despite some consistency in the relative value of some outcome domains for chronic gout studies, there is sufficient disagreement in the relative importance of other domains of outcome to challenge the validity of constructing a composite index of response that would be applicable to most gout patients.

The experience of having psoriasis through the lens of the International Classification of Functioning, Disability and Health (ICF)

BACKGROUND/OBJECTIVE

The International Classification of Functioning, Disability and Health (ICF) was developed by the World Health Organization to comprehensively describe the ways that health conditions can affect people. The identification of ICF categories of most relevance to people with a particular disease can increase the usefulness of the ICF and create a reference for outcome studies. This study aimed to ascertain, through focus group interviews with psoriasis patients and an online Delphi survey with health professionals, the impacts of psoriasis as categorised by the ICF.

METHODS

We conducted and transcribed verbatim focus group interviews with 32 outpatients with psoriasis from two New Zealand cities. The interview transcripts were analysed to yield meaning units and concepts contained in the meaning units were extracted. These concepts were linked to ICF categories. An online Delphi survey among 23 health professionals was conducted to obtain similar information. The ICF categories were rated for their perceived relevance to psoriasis by health professionals over three iterations.

RESULTS

In total, 32 patients participated in six focus groups. Interview saturation was reached after five focus groups. The concepts were linked to 83 ICF categories and two separate health conditions. Among health professionals, 167 ICF categories were rated, mostly in the moderately relevant (four to six) range.

CONCLUSION

Applying the established method of meaning condensation to focus group interview transcripts allowed the accurate linking of concepts to ICF categories. This will be of use to researchers developing the first ICF core set for psoriasis in the future.

New classification criteria for gout: a framework for progress

The definitive classification or diagnosis of gout normally relies upon the identification of MSU crystals in SF or from tophi. Where microscopic examination of SF is not available or is impractical, the best approach may differ depending upon the context. For many types of research, clinical classification criteria are necessary. The increasing prevalence of gout, advances in therapeutics and the development of international research collaborations to understand the impact, mechanisms and optimal treatment of this condition emphasize the need for accurate and uniform classification criteria for gout. Five clinical classification criteria for gout currently exist. However, none of the currently available criteria has been adequately validated. An international project is currently under way to develop new validated gout classification criteria. These criteria will be an essential step forward to advance the research agenda in the modern era of gout management.

A delphi exercise to identify characteristic features of gout - opinions from patients and physicians, the first stage in developing new classification criteria

OBJECTIVE

To identify a comprehensive list of features that might discriminate between gout and other rheumatic musculoskeletal conditions, to be used subsequently for a case-control study to develop and test new classification criteria for gout.

METHODS

Two Delphi exercises were conducted using Web-based questionnaires: one with physicians from several countries who had an interest in gout and one with patients from New Zealand who had gout. Physicians rated a list of potentially discriminating features that were identified by literature review and expert opinion, and patients rated a list of features that they generated themselves. Agreement was defined by the RAND/UCLA disagreement index.

RESULTS

Forty-four experienced physicians and 9 patients responded to all iterations. For physicians, 71 items were identified by literature review and 15 more were suggested by physicians. The physician survey showed agreement for 26 discriminatory features and 15 as not discriminatory. The patients identified 46 features of gout, for which there was agreement on 25 items as being discriminatory and 7 items as not discriminatory.

CONCLUSION

Patients and physicians agreed upon several key features of gout. Physicians emphasized objective findings, imaging, and patterns of symptoms, whereas patients emphasized severity, functional results, and idiographic perception of symptoms.

Years lived with disability (YLDs) for 1160 sequelae of 289 diseases and injuries 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010

BACKGROUND

Non-fatal health outcomes from diseases and injuries are a crucial consideration in the promotion and monitoring of individual and population health. The Global Burden of Disease (GBD) studies done in 1990 and 2000 have been the only studies to quantify non-fatal health outcomes across an exhaustive set of disorders at the global and regional level. Neither effort quantified uncertainty in prevalence or years lived with disability (YLDs).

METHODS

Of the 291 diseases and injuries in the GBD cause list, 289 cause disability. For 1160 sequelae of the 289 diseases and injuries, we undertook a systematic analysis of prevalence, incidence, remission, duration, and excess mortality. Sources included published studies, case notification, population-based cancer registries, other disease registries, antenatal clinic serosurveillance, hospital discharge data, ambulatory care data, household surveys, other surveys, and cohort studies. For most sequelae, we used a Bayesian meta-regression method, DisMod-MR, designed to address key limitations in descriptive epidemiological data, including missing data, inconsistency, and large methodological variation between data sources. For some disorders, we used natural history models, geospatial models, back-calculation models (models calculating incidence from population mortality rates and case fatality), or registration completeness models (models adjusting for incomplete registration with health-system access and other covariates). Disability weights for 220 unique health states were used to capture the severity of health loss. YLDs by cause at age, sex, country, and year levels were adjusted for comorbidity with simulation methods. We included uncertainty estimates at all stages of the analysis.

FINDINGS

Global prevalence for all ages combined in 2010 across the 1160 sequelae ranged from fewer than one case per 1 million people to 350,000 cases per 1 million people. Prevalence and severity of health loss were weakly correlated (correlation coefficient -0·37). In 2010, there were 777 million YLDs from all causes, up from 583 million in 1990. The main contributors to global YLDs were mental and behavioural disorders, musculoskeletal disorders, and diabetes or endocrine diseases. The leading specific causes of YLDs were much the same in 2010 as they were in 1990: low back pain, major depressive disorder, iron-deficiency anaemia, neck pain, chronic obstructive pulmonary disease, anxiety disorders, migraine, diabetes, and falls. Age-specific prevalence of YLDs increased with age in all regions and has decreased slightly from 1990 to 2010. Regional patterns of the leading causes of YLDs were more similar compared with years of life lost due to premature mortality. Neglected tropical diseases, HIV/AIDS, tuberculosis, malaria, and anaemia were important causes of YLDs in sub-Saharan Africa.

INTERPRETATION

Rates of YLDs per 100,000 people have remained largely constant over time but rise steadily with age. Population growth and ageing have increased YLD numbers and crude rates over the past two decades. Prevalences of the most common causes of YLDs, such as mental and behavioural disorders and musculoskeletal disorders, have not decreased. Health systems will need to address the needs of the rising numbers of individuals with a range of disorders that largely cause disability but not mortality. Quantification of the burden of non-fatal health outcomes will be crucial to understand how well health systems are responding to these challenges. Effective and affordable strategies to deal with this rising burden are an urgent priority for health systems in most parts of the world.

FUNDING

Bill & Melinda Gates Foundation.

Disability-adjusted life years (DALYs) for 291 diseases and injuries in 21 regions, 1990-2010: a systematic analysis for the Global Burden of Disease Study 2010

BACKGROUND

Measuring disease and injury burden in populations requires a composite metric that captures both premature mortality and the prevalence and severity of ill-health. The 1990 Global Burden of Disease study proposed disability-adjusted life years (DALYs) to measure disease burden. No comprehensive update of disease burden worldwide incorporating a systematic reassessment of disease and injury-specific epidemiology has been done since the 1990 study. We aimed to calculate disease burden worldwide and for 21 regions for 1990, 2005, and 2010 with methods to enable meaningful comparisons over time.

METHODS

We calculated DALYs as the sum of years of life lost (YLLs) and years lived with disability (YLDs). DALYs were calculated for 291 causes, 20 age groups, both sexes, and for 187 countries, and aggregated to regional and global estimates of disease burden for three points in time with strictly comparable definitions and methods. YLLs were calculated from age-sex-country-time-specific estimates of mortality by cause, with death by standardised lost life expectancy at each age. YLDs were calculated as prevalence of 1160 disabling sequelae, by age, sex, and cause, and weighted by new disability weights for each health state. Neither YLLs nor YLDs were age-weighted or discounted. Uncertainty around cause-specific DALYs was calculated incorporating uncertainty in levels of all-cause mortality, cause-specific mortality, prevalence, and disability weights.

FINDINGS

Global DALYs remained stable from 1990 (2·503 billion) to 2010 (2·490 billion). Crude DALYs per 1000 decreased by 23% (472 per 1000 to 361 per 1000). An important shift has occurred in DALY composition with the contribution of deaths and disability among children (younger than 5 years of age) declining from 41% of global DALYs in 1990 to 25% in 2010. YLLs typically account for about half of disease burden in more developed regions (high-income Asia Pacific, western Europe, high-income North America, and Australasia), rising to over 80% of DALYs in sub-Saharan Africa. In 1990, 47% of DALYs worldwide were from communicable, maternal, neonatal, and nutritional disorders, 43% from non-communicable diseases, and 10% from injuries. By 2010, this had shifted to 35%, 54%, and 11%, respectively. Ischaemic heart disease was the leading cause of DALYs worldwide in 2010 (up from fourth rank in 1990, increasing by 29%), followed by lower respiratory infections (top rank in 1990; 44% decline in DALYs), stroke (fifth in 1990; 19% increase), diarrhoeal diseases (second in 1990; 51% decrease), and HIV/AIDS (33rd in 1990; 351% increase). Major depressive disorder increased from 15th to 11th rank (37% increase) and road injury from 12th to 10th rank (34% increase). Substantial heterogeneity exists in rankings of leading causes of disease burden among regions.

INTERPRETATION

Global disease burden has continued to shift away from communicable to non-communicable diseases and from premature death to years lived with disability. In sub-Saharan Africa, however, many communicable, maternal, neonatal, and nutritional disorders remain the dominant causes of disease burden. The rising burden from mental and behavioural disorders, musculoskeletal disorders, and diabetes will impose new challenges on health systems. Regional heterogeneity highlights the importance of understanding local burden of disease and setting goals and targets for the post-2015 agenda taking such patterns into account. Because of improved definitions, methods, and data, these results for 1990 and 2010 supersede all previously published Global Burden of Disease results.

FUNDING

Bill & Melinda Gates Foundation.

Prescription and dosing of urate-lowering therapy, rather than patient behaviours, are the key modifiable factors associated with targeting serum urate in gout

Background

Long term serum urate (SU) lowering to a target of <0.36 mmol/l (6 mg/dl) is recommended for effective gout management. However, many studies have reported low achievement of SU targets. The aim of this cross-sectional study was to examine the clinical and psychological factors associated with SU targets in patients with gout.

Methods

Patients with gout for <10 years were recruited from primary and secondary care settings. SU target was defined as SU concentration <0.36 mmol/L at the time of the study visit. Both clinical and psychological factors associated with SU target were analysed. The relationship between SU target and measures of gout activity such as flare frequency, tophi, work absences, and Health Assessment Questionnaire-II was also analysed.

Results

Of the 273 patients enrolled into the study, 89 (32.6%) had SU concentration <0.36 mmol/L. Urate-lowering therapy (ULT) use was strongly associated with SU target (p < 0.001). In those patients prescribed ULT (n = 181), allopurinol dose, patient confidence to keep SU under control, female sex, and ethnicity were independently associated with SU target. Other patient psychological measures and health-related behaviours, including adherence scores, were not independently associated with SU target in those taking ULT. Creatinine clearance, diuretic use, age, and body mass index were not associated with SU target. Patients at SU target reported lower gout flare frequency, compared with those not at target (p = 0.03).

Conclusions

ULT prescription and dosing are key modifiable factors associated with achieving SU target. These data support interventions focusing on improved use of ULT to optimise outcomes in patients with gout.

Developing a provisional definition of flare in patients with established gout

OBJECTIVE

Various nonvalidated criteria for disease flare have been used in studies of gout. Our objective was to develop empirical definitions for a gout flare from patient-reported features.

METHODS

Possible elements for flare criteria were previously reported. Data were collected from 210 gout patients at 8 international sites to evaluate potential gout flare criteria against the gold standard of an expert rheumatologist definition. Flare definitions based on the presence of the number of criteria independently associated with the flare and classification and regression tree approaches were developed.

RESULTS

The mean ± SD age of the study participants was 56.2 ± 15 years, 207 of them (98%) were men, and 54 of them (26%) had flares of gout. The presence of any patient-reported warm joint, any patient-reported swollen joint, patient-reported pain at rest score of >3 (0-10 scale), and patient-reported flare were independently associated with the study gold standard. The greatest discriminating power was noted for the presence of 3 or more of the above 4 criteria (sensitivity 91% and specificity 82%). Requiring all 4 criteria provided the highest specificity (96%) and positive predictive value (85%). A classification tree identified pain at rest with a score of >3, followed by patient self-reported flare, as the rule associated with the gold standard (sensitivity 83% and specificity 90%).

CONCLUSION

We propose definitions for a disease flare based on self-reported items in patients previously diagnosed as having gout. Patient-reported flare, joint pain at rest, warm joints, and swollen joints were most strongly associated with presence of a gout flare. These provisional definitions will next be validated in clinical trials.

Potential unmet need for gout diagnosis and treatment: capture-recapture analysis of a national administrative dataset

OBJECTIVE

To estimate the degree of undercount of people diagnosed with gout in administrative datasets using capture-recapture methods.

METHODS

Hospitalization and drug dispensing claims (allopurinol or colchicine) data for all Aotearoa New Zealand were used to estimate the prevalence of gout in 2009 (n = 4 295 296). As a comparison, we calculated gout prevalence using a large primary care dataset using general practitioner diagnosis and prescribing records (n = 555 313). For each of these datasets, we estimated the undercount through capture-recapture analysis using a Poisson regression model. A two-list model was used, which included covariates such as age, gender, ethnic groups and New Zealand deprivation quintiles.

RESULTS

The crude prevalence of diagnosed gout in the Aotearoa New Zealand population aged ≥ 20 years was 3.75%. The covariate-adjusted capture-recapture estimate of those not recorded but likely to have gout was 0.92%, giving an overall estimated prevalence of 4.67% (95% CI 4.49, 4.90%) for the population aged ≥ 20 years. This amounts to 80% of people with gout being identified by the algorithm for the Aotearoa New Zealand data-that is being recorded in either lists of dispensing of allopurinol or colchicine or hospital discharge. After capture-recapture, gout prevalence for all males aged ≥ 20 years was 7.3% and in older (≥ 65 years) Māori and Pacific men was >30%.

CONCLUSION

Capture-recapture analysis of administrative datasets provides a readily available method for estimating an aspect of unmet need in the population-in this instance potentially 20% of those with gout not being identified and treated specifically for this condition.

Systematic review of the prevalence of gout and hyperuricaemia in Australia

AIMS

Gout is a growing health problem worldwide especially in affluent countries, such as Australia. Gout and hyperuricaemia are associated with the metabolic syndrome, diabetes mellitus, obesity and hypertension. More importantly, Australia has a growing prevalence of these important health problems. The aim of this study was to systematically review published information regarding the prevalence of gout and hyperuricaemia in Australia.

METHODS

A systematic search was undertaken of the MEDLINE, EMBASE and Web of Science databases, as well as relevant websites for journal articles and reports relating to the prevalence of hyperuricaemia and gout in Australia.

RESULTS

Twenty-five journal articles and five reports were included in the review. Data collected in a standardised way show gout increased in prevalence from 0.5% population prevalence to 1.7% population prevalence from 1968 to 1995/1996. There has been a significant rise in the prevalence of gout in the Australian Aboriginal population from 0% in 1965 to 9.7% in men and 2.9% in women in 2002. Consistent with the rise in gout prevalence, serum uric acid in blood donors has increased from 1959 to 1980 (17% in 30- to 40-year-old men).

CONCLUSIONS

The rate of gout and hyperuricaemia in Australia is high in relation to comparable countries and is increasing. The prevalence of gout in elderly male Australians is second only to New Zealand, which has the highest reported rate in the world. Further research on Aboriginal and Torres Strait Islander gout and hyperuricaemia is required as a result of the lack of contemporary data.

Serum urate in chronic gout--will it be the first validated soluble biomarker in rheumatology?

OBJECTIVE

To summarize evidence for and endorsement of serum urate (SU) as having fulfilled the OMERACT filter as a soluble biomarker in chronic gout at the 2010 Outcome Measures in Rheumatology Meeting (OMERACT 10).

METHODS

Data were presented to support the use of SU as a soluble biomarker in chronic gout and specifically the ability to utilize it to predict future patient-reported outcomes.

RESULTS

SU was accepted as having fulfilled the OMERACT filter by 78% of voters. However, consensus was not obtained regarding its use as a soluble biomarker in chronic gout. Although the majority of the criteria for a soluble biomarker were fulfilled, the key criterion of association of the biomarker with outcomes was not agreed upon. It was agreed that the appropriate choice of endpoint must be linked to its clinical importance to the individual with the disorder and its temporal relationship to the intervention. Appropriate outcomes in chronic gout may therefore include gout flares, reduction in tophi, and patient-reported outcomes.

CONCLUSION

SU is a critical outcome measure. It has the potential to fulfil criteria for a soluble biomarker. Further analyses of existing data from randomized controlled trials will be required to determine whether SU can predict future important outcomes, in particular disability.