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1.  A Review of Uric Acid, Crystal Deposition Disease, and Gout 
Advances in Therapy  2014;32:31-41.
There has been increased interest in gout in both academic and clinical practice settings. Several reasons may explain this. The prevalence of both hyperuricemia and gout has risen in the last decades in developed countries and therefore the burden of gout has increased. The association of hyperuricemia and gout with cardiovascular outcomes and the opportunity of further benefits of intervention on hyperuricemia have been recently highlighted in the literature. Imaging techniques have proven to be useful for detection of urate deposition, even prior to the first clinical symptoms, enabling the evaluation of the extent of deposition and providing objective measurement of crystal depletion during urate-lowering treatment. Treating to target is increasingly used as the approach to treatment of diverse diseases. Therefore, different targets have been recommended for different stages of the burden of disease and for different stages of treatment. The final strategic target, to which any effort should be taken into consideration, is to completely dissolve urate crystals in tissues and therefore avoid further symptoms and structural damage of involved musculoskeletal structures. In summary, evidence suggest that an early approach to the treatment of gout and associated comorbidities is advisable, that new imaging techniques may help to evaluate both the burden of deposition and response to urate-lowering treatment in selected patients, and finally that the final strategic objective of healthcare for patients with gout is to completely resolve urate crystal deposits.
Electronic supplementary material
The online version of this article (doi:10.1007/s12325-014-0175-z) contains supplementary material, which is available to authorized users.
doi:10.1007/s12325-014-0175-z
PMCID: PMC4311063  PMID: 25533440
Crystal deposition disease; Gout; Hyperuricemia; Uric acid
2.  Quadriceps arthrogenic muscle inhibition: the effects of experimental knee joint effusion on motor cortex excitability 
Introduction
Marked weakness of the quadriceps muscles is typically observed following injury, surgery or pathology affecting the knee joint. This is partly due to ongoing neural inhibition that prevents the central nervous system from fully activating the quadriceps, a process known as arthrogenic muscle inhibition (AMI). This study aimed to further investigate the mechanisms underlying AMI by exploring the effects of experimental knee joint effusion on quadriceps corticomotor and intracortical excitability.
Methods
Seventeen healthy volunteers participated in this study. Transcranial magnetic stimulation was used to measure quadriceps motor evoked potential area, short-interval intracortical inhibition, intracortical facilitation and cortical silent period duration before and after experimental knee joint effusion. Joint effusion was induced by the intraarticular infusion of dextrose saline into the knee.
Results
There was a significant increase in quadriceps motor evoked potential area following joint infusion, both at rest (P = 0.01) and during voluntary muscle contraction (P = 0.02). Cortical silent period duration was significantly reduced following joint infusion (P = 0.02). There were no changes in short interval intracortical inhibition or intracortical facilitation over time (all P > 0.05).
Conclusions
The results of this study provide no evidence for a supraspinal contribution to quadriceps AMI. Paradoxically, but consistent with previous observations in patients with chronic knee joint pathology, quadriceps corticomotor excitability increased after experimental knee joint effusion. The increase in quadriceps corticomotor excitability may be at least partly mediated by a decrease in gamma-aminobutyric acid (GABA)-ergic inhibition within the motor cortex.
doi:10.1186/s13075-014-0502-4
PMCID: PMC4271337  PMID: 25497133
3.  Impaired response or insufficient dosage? – examining the potential causes of ”inadequate response” to allopurinol in the treatment of gout 
Objectives
Gout is one of the most common forms of arthritis. It is well established that urate lowering therapy that aims for a serum urate less than at least 0.36mmol/l (6mg/dL) is required for successful management of gout. Allopurinol, a xanthine oxidase (XO) inhibitor is the most commonly used urate lowering therapy. However, many patients fail to achieve the target serum urate on allopurinol, these patients can be considered to have “inadequate response” to allopurinol. Herein we examine the potential mechanisms and implications of inadequate response to allopurinol.
Methods
The literature was reviewed for potential causes for failure to reach target serum urate in patients receiving allopurinol.
Results
The two most common causes of inadequate response to allopurinol are poor adherence and under-dosing of allopurinol. Adherent patients who fail to achieve target serum urate on standard doses of allopurinol form a group that could be considered to be “partially resistant” to allopurinol. There are four potential mechanisms for partial allopurinol resistance: decreased conversion of allopurinol to oxypurinol; increased renal excretion of oxypurinol; abnormality in XO structure and or function such that oxypurinol is rendered less effective, and/or drug interactions.
Conclusions
It is important to determine the reasons for failure to achieve treatment targets with allopurinol, particularly as newer agents become available. The knowledge of the mechanisms for inadequate response may help guide the clinician toward making a therapeutic choice that is more likely to result in achieving the serum urate target.
doi:10.1016/j.semarthrit.2014.05.007
PMCID: PMC4225179  PMID: 24925693
4.  The relationship of apolipoprotein B and very low density lipoprotein triglyceride with hyperuricemia and gout 
Introduction
Gout results from an innate immune response to monosodium urate (MSU) crystals deposited in joints. Increased very low-density lipoprotein (VLDL) has been associated with gout. The apolipoprotein B (apo B), which is present on VLDL, regulates neutrophil response to MSU crystals and has been positively associated with gout. Furthermore, the gene (A1CF) encoding the complementation factor for the APOB mRNA-editing enzyme is associated with urate levels. However, the relationship of apo B and VLDL with gout and hyperuricaemia (HU) is still unclear. Therefore, we tested the association of VLDL and apo B with HU and with gout compared to HU.
Methods
New Zealand European (n = 90) and Māori and Pacific Island (Polynesian) (n = 90) male gout case and control sample sets were divided into normouricaemia (NU), asymptomatic HU and gout groups. Size exclusion chromatography and enzyme-linked immunosorbant assay was used to measure VLDL and apo B. Multivariate logistic regression was used to assess the risk of gout and HU per unit change in VLDL and apo B.
Results
Increased levels of VLDL triglycerides (Tg) were observed in the gout sample set compared to NU and HU in Europeans (P = 1.8 × 10-6 and 1 × 10-3, respectively), but only compared to NU in Polynesians (P = 0.023). This increase was driven by increased number of VLDL particles in the European participants and by the Tg-enrichment of existing VLDL particles in the Polynesian participants. Each mmol/L increase in VLDL Tg was significantly associated with gout in the presence of HU in Europeans, with a similar trend in Polynesians (OR = 7.61, P = 0.011 and 2.84, P = 0.069, respectively). Each μmol/L increase in total apo B trended towards decreased risk of HU (OR = 0.47; P = 0.062) and, conversely, with increased risk of gout compared to HU (OR = 5.60; P = 0.004).
Conclusions
Increased VLDL Tg is associated with the risk of gout compared to HU. A genetic approach should be taken to investigate the possibility for causality of VLDL in gout. Apolipoprotein B may have pleiotropic effects in determining HU and gout.
doi:10.1186/s13075-014-0495-z
PMCID: PMC4265487  PMID: 25432151
5.  Outcome measures in acute gout: a systematic literature review 
The Journal of rheumatology  2013;41(3):558-568.
Objective
Five core domains have been endorsed by Outcomes Measures in Rheumatology (OMERACT) for acute gout: pain, joint swelling, joint tenderness, patient global assessment, and activity limitation. The aim of this work was to evaluate 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 two reviewers to summarise 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 100mm visual analog scale (VAS) and 5-point Likert scale. Both methods have high feasibility, face and content validity, 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.
doi:10.3899/jrheum.131244
PMCID: PMC4217650  PMID: 24334652
gout; pain; measurement; outcome
6.  Application of the OMERACT filter to measures of core outcome domains in recent clinical studies of acute gout 
The Journal of rheumatology  2014;41(3):574-580.
Objective
To determine the extent to which instruments that measure core outcome domains in acute gout fulfil the OMERACT filter requirements of truth, discrimination and feasibility.
Methods
Patient-level data from four randomised controlled trials of agents designed to treat acute gout and one observational study of acute gout were analysed. 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 generalised estimating equations were assessed. Floor and ceiling effects were also assessed and MCID 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, 0 to 100 mm visual analogue scale). 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.
Conclusions
There is sufficient evidence to support measures of pain (using Likert, numeric rating scale or visual analogue scales), 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.
doi:10.3899/jrheum.131245
PMCID: PMC4212978  PMID: 24429178
gout; outcome measures; psychometrics
7.  New classification criteria for gout: a framework for progress 
Rheumatology (Oxford, England)  2013;52(10):1748-1753.
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.
doi:10.1093/rheumatology/ket154
PMCID: PMC4047282  PMID: 23611919
gout; classification; urate; research
8.  OMERACT endorsement of measures of outcome for studies of acute gout 
The Journal of rheumatology  2013;41(3):569-573.
Objective
To determine the extent to which OMERACT participants agree that instruments that have been used in clinical trials and measure OMERACT core outcome domains in acute gout fulfil the filter requirements of truth, discrimination and feasibility and to determine where future research efforts need to be directed.
Methods
The 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 VAS (0 to 100mm) 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.
Conclusions
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.
doi:10.3899/jrheum.131246
PMCID: PMC4162875  PMID: 24334651
gout; outcome measures; psychometrics
9.  Influence of the ABCG2 gout risk 141 K allele on urate metabolism during a fructose challenge 
Introduction
Both genetic variation in ATP-binding cassette sub-family G member 2 (ABCG2) and intake of fructose-containing beverages are major risk factors for hyperuricemia and gout. This study aimed to test the hypothesis that the ABCG2 gout risk allele 141 K promotes the hyperuricaemic response to fructose loading.
Methods
Healthy volunteers (n = 74) provided serum and urine samples immediately before and 30, 60, 120 and 180 minutes after ingesting a 64 g fructose solution. Data were analyzed based on the presence or absence of the ABCG2 141 K gout risk allele.
Results
The 141 K risk allele was present in 23 participants (31%). Overall, serum urate (SU) concentrations during the fructose load were similar in those with and without the 141 K allele (PSNP = 0.15). However, the 141 K allele was associated with a smaller increase in SU following fructose intake (PSNP <0.0001). Those with the 141 K allele also had a smaller increase in serum glucose following the fructose load (PSNP = 0.002). Higher fractional excretion of uric acid (FEUA) at baseline and throughout the fructose load was observed in those with the 141 K risk allele (PSNP <0.0001). However, the change in FEUA in response to fructose was not different in those with and without the 141 K risk allele (PSNP = 0.39). The 141 K allele effects on serum urate and glucose were more pronounced in Polynesian participants and in those with a body mass index ≥25 kg/m2.
Conclusions
In contrast to the predicted responses for a hyperuricemia/gout risk allele, the 141 K allele is associated with smaller increases in SU and higher FEUA following a fructose load. The results suggest that ABCG2 interacts with extra-renal metabolic pathways in a complex manner to regulate SU and gout risk.
Clinical Trials Registration
The study was registered by the Australian Clinical Trials Registry (ACTRN12610001036000).
doi:10.1186/ar4463
PMCID: PMC3978630  PMID: 24476385
10.  MRI osteitis predicts cartilage damage at the wrist in RA: a three-year prospective 3T MRI study examining cartilage damage 
Introduction
Cartilage damage impacts on patient disability in rheumatoid arthritis (RA). The aims of this magnetic resonance imaging (MRI) study were to investigate cartilage damage over three years and determine predictive factors.
Methods
A total of 38 RA patients and 22 controls were enrolled at t = 0 (2009). After 3 years, clinical and MRI data were available in 28 patients and 15 controls. 3T MRI scans were scored for cartilage damage, bone erosion, synovitis and osteitis. A model was developed to predict cartilage damage from baseline parameters.
Results
Inter-reader reliability for the Auckland MRI cartilage score (AMRICS) was high for status scores; intraclass correlation coefficient (ICC), 0.90 (0.81 to 0.95) and moderate for change scores (ICC 0.58 (0.24 to 0.77)). AMRICS scores correlated with the Outcome MEasures in Rheumatoid Arthritis Clinical Trials (OMERACT) MRI joint space narrowing (jsn) and X-Ray (XR) jsn scores (r =0.96, P < 0.0001 and 0.80, P < 0.0001, respectively). AMRICS change scores were greater for RA patients than controls (P = 0.06 and P = 0.04 for the two readers). Using linear regression, baseline MRI cartilage, synovitis and osteitis scores predicted the three-year AMRICS (R2 = 0.67, 0.37 and 0.39, respectively). A multiple linear regression model predicted the three-year AMRICS (R2 = 0.78). Baseline radial osteitis predicted increased cartilage scores at the radiolunate and radioscaphoid joints, P = 0.0001 and 0.0012, respectively and synovitis at radioulnar, radiocarpal and intercarpal-carpometacarpal joints also influenced three-year cartilage scores (P-values of 0.001, 0.04 and 0.01, respectively).
Conclusions
MRI cartilage damage progression is preceded by osteitis and synovitis but is most influenced by pre-existing cartilage damage suggesting primacy of the cartilage damage pathway in certain patients.
doi:10.1186/ar4462
PMCID: PMC3978660  PMID: 24476340
11.  Tophus measurement as an outcome measure for clinical trials of chronic gout: progress and research priorities 
The Journal of rheumatology  2011;38(7):10.3899/jrheum.110272.
Despite the recognition that tophus regression is an important outcome measure in clinical trials of chronic gout, there is no agreed method of tophus measurement. A number of methods have been used in clinical trials of chronic gout, from simple physical measurement techniques to complex advanced imaging methods. This paper summarises the methods of tophus measurement that have been used and discusses the properties of these methods. Physical measurement using Vernier calipers fulfils most aspects of the Outcomes Measures in Rheumatology (OMERACT) filter. Rigorous testing of the complex methods, particularly with respect to reliability and sensitivity to change is needed, to determine the appropriate use of these methods. Further information is also required regarding which method of physical measurement is best for use in future clinical trials. The need to develop and test a patient reported measure of tophus burden is also highlighted.
doi:10.3899/jrheum.110272
PMCID: PMC3882031  PMID: 21724716
12.  Association analysis of the SLC22A11 (organic anion transporter 4) and SLC22A12 (urate transporter 1) urate transporter locus with gout in New Zealand case-control sample sets reveals multiple ancestral-specific effects 
Arthritis Research & Therapy  2013;15(6):R220.
Introduction
There is inconsistent association between urate transporters SLC22A11 (organic anion transporter 4 (OAT4)) and SLC22A12 (urate transporter 1 (URAT1)) and risk of gout. New Zealand (NZ) Māori and Pacific Island people have higher serum urate and more severe gout than European people. The aim of this study was to test genetic variation across the SLC22A11/SLC22A12 locus for association with risk of gout in NZ sample sets.
Methods
A total of 12 single nucleotide polymorphism (SNP) variants in four haplotype blocks were genotyped using TaqMan® and Sequenom MassArray in 1003 gout cases and 1156 controls. All cases had gout according to the 1977 American Rheumatism Association criteria. Association analysis of single markers and haplotypes was performed using PLINK and Stata.
Results
A haplotype block 1 SNP (rs17299124) (upstream of SLC22A11) was associated with gout in less admixed Polynesian sample sets, but not European Caucasian (odds ratio; OR = 3.38, P = 6.1 × 10-4; OR = 0.91, P = 0.40, respectively) sample sets. A protective block 1 haplotype caused the rs17299124 association (OR = 0.28, P = 6.0 × 10-4). Within haplotype block 2 (SLC22A11) we could not replicate previous reports of association of rs2078267 with gout in European Caucasian (OR = 0.98, P = 0.82) sample sets, however this SNP was associated with gout in Polynesian (OR = 1.51, P = 0.022) sample sets. Within haplotype block 3 (including SLC22A12) analysis of haplotypes revealed a haplotype with trans-ancestral protective effects (OR = 0.80, P = 0.004), and a second haplotype conferring protection in less admixed Polynesian sample sets (OR = 0.63, P = 0.028) but risk in European Caucasian samples (OR = 1.33, P = 0.039).
Conclusions
Our analysis provides evidence for multiple ancestral-specific effects across the SLC22A11/SLC22A12 locus that presumably influence the activity of OAT4 and URAT1 and risk of gout. Further fine mapping of the association signal is needed using trans-ancestral re-sequence data.
doi:10.1186/ar4417
PMCID: PMC3978909  PMID: 24360580
13.  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.
doi:10.1186/1471-2474-14-363
PMCID: PMC3878111  PMID: 24359261
Gout; Tophus; Kidney; Creatinine
14.  Patient-reported Outcomes in Chronic Gout: A Report from OMERACT 10 
The Journal of rheumatology  2011;38(7):10.3899/jrheum.110271.
Objective
To summarize the endorsement of measures of patient-reported outcome (PRO) domains in chronic gout at the 2010 Outcome Measures in Rheumatology Meeting (OMERACT 10).
Methods
During the OMERACT 10 gout workshop, validation data were presented for key PRO domains including pain [pain by visual analog scale (VAS)], patient global (patient global VAS), activity limitation [Health Assessment Questionnaire-Disability Index (HAQ-DI)], and a disease-specific measure, the Gout Assessment Questionnaire version 2.0 (GAQ v2.0). Data were presented on all 3 aspects of the OMERACT filters of truth, discrimination, and feasibility. One PRO, health-related quality of life measurement with the Medical Outcomes Study Short-form 36 (SF-36), was previously endorsed at OMERACT 9.
Results
One measure for each of the 3 PRO of pain, patient global, and activity limitation was endorsed by > 70% of the OMERACT delegates to have appropriate validation data. Specifically, pain measurement by VAS was endorsed by 85%, patient global assessment by VAS by 73%, and activity limitation by HAQ-DI by 71%. GAQ v2.0 received 30% vote and was not endorsed due to several concerns including low internal consistency and lack of familiarity with the measure. More validation studies are needed for this measure.
Conclusion
With the endorsement of one measure each for pain, patient global, SF-36, and activity limitation, all 4 PRO for chronic gout have been endorsed. Future validation studies are needed for the disease-specific measure, GAQ v2.0. Validation for PRO for acute gout will be the focus of the next validation exercise for the OMERACT gout group.
doi:10.3899/jrheum.110271
PMCID: PMC3850171  PMID: 21724715
PATIENT-REPORTED OUTCOMES; CHRONIC GOUT; VALIDATION; PAIN; PATIENT GLOBAL; FUNCTIONAL LIMITATION
15.  Association of the lipoprotein receptor-related protein 2 gene with gout and non-additive interaction with alcohol consumption 
Arthritis Research & Therapy  2013;15(6):R177.
Introduction
The T allele of a single nucleotide polymorphism (SNP: rs2544390) in lipoprotein receptor-related protein 2 (LRP2) is associated with higher serum urate and risk of gout in Japanese individuals. SNP rs2544390 also interacts with alcohol consumption in determining hyperuricemia in this population. We investigated the association of rs2544390 with gout, and interaction with all types of alcohol consumption in European and New Zealand (NZ) Māori and Pacific subjects, and a Māori study cohort from the East Coast region of NZ’s North Island.
Methods
Rs2544390 was genotyped by Taqman®. From NZ a total of 1205 controls and 1431 gout cases clinically ascertained were used. Publicly available genotype and serum urate data were utilized from the Atherosclerosis Risk in Communities (ARIC) study and the Framingham Heart Study (FHS). Alcohol consumption data were obtained by consumption frequency questions in all study cohorts. Multivariate adjusted logistic regression was done using STATA.
Results
The T allele of rs2544390 was associated with increased risk of gout in the combined Māori and Pacific Island cohort (OR = 1.20, P = 0.009), and associated with gout in the European subjects, but with a protective effect (OR = 0.79, PUnadjusted = 0.02). Alcohol consumption was positively associated with risk of gout in Māori and Pacific subjects (0.2% increased risk/g/week, P = 0.004). There was a non-additive interaction between any alcohol intake and the risk of gout in the combined Māori and Pacific cohorts (PInteraction = 0.001), where any alcohol intake was associated with a 4.18-fold increased risk in the CC genotype group (P = 6.6x10-5), compared with a 1.14-fold increased risk in the CT/TT genotype group (P = 0.40). These effects were not observed in European subjects.
Conclusions
Association of the T-allele with gout risk in the Māori and Pacific subjects was consistent with this allele increasing serum urate in Japanese individuals. The non-additive interaction in the Māori and Pacific subjects showed that alcohol consumption over-rides any protective effect conferred by the CC genotype. Further exploration of the mechanism underlying this interaction should generate new understanding of the biological role of alcohol in gout, in addition to strengthening the evidence base for reduction of alcohol consumption in the management of gout.
doi:10.1186/ar4366
PMCID: PMC3979038  PMID: 24286387
16.  Lack of change in urate deposition by dual-energy computed tomography among clinically stable patients with long-standing tophaceous gout: a prospective longitudinal study 
Arthritis Research & Therapy  2013;15(5):R160.
Introduction
Dual-energy computed tomography (DECT) has potential for monitoring urate deposition in patients with gout. The aim of this prospective longitudinal study was to analyse measurement error of DECT urate volume measurement in clinically stable patients with tophaceous gout.
Methods
Seventy-three patients with tophaceous gout on stable therapy attended study visits at baseline and twelve months. All patients had a comprehensive clinical assessment including serum urate testing and DECT scanning of both feet. Two readers analysed the DECT scans for the total urate volume in both feet. Analysis included inter-reader intraclass correlation coefficients (ICCs) and limits of agreement, and calculation of the smallest detectable change.
Results
Mean (standard deviation) serum urate concentration over the study period was 0.38 (0.09) mmol/L. Urate-lowering therapy was prescribed in 70 (96%) patients. The median (interquartile range) baseline DECT urate volume was 0.49 (0.16, 2.18) cm3, and change in DECT urate volume was -0.01 (-0.40, 0.28) cm3. Inter-reader ICCs were 1.00 for baseline DECT volumes and 0.93 for change values. Inter-reader bias (standard deviation) for baseline volumes was -0.18 (0.63) cm3 and for change was -0.10 (0.93) cm3. The smallest detectable change was 0.91 cm3. There were 47 (64%) patients with baseline DECT urate volumes <0.91 cm3. Higher serum urate concentrations were observed in patients with increased DECT urate volumes above the smallest detectable change (P = 0.006). However, a relationship between changes in DECT urate volumes and serum urate concentrations was not observed in the entire group.
Conclusions
In patients with tophaceous gout on stable conventional urate-lowering therapy the measurement error for DECT urate volume assessment is substantially greater than the median baseline DECT volume. Analysis of patients commencing or intensifying urate-lowering therapy should clarify the optimal use of DECT as a potential outcome measure in studies of chronic gout.
doi:10.1186/ar4343
PMCID: PMC3978645  PMID: 24286500
19.  The effects of commercially available footwear on foot pain and disability in people with gout: a pilot study 
Background
There is limited evidence on non-pharmacological interventions for gout. The aim of the study was to determine whether a footwear intervention can reduce foot pain and musculoskeletal disability in people with gout.
Methods
Thirty-six people with gout participated in a prospective intervention study over 8 weeks. Participants selected one of 4 pairs of shoes and thereafter wore the shoes for 8 weeks. The primary outcome was foot pain using a 100 mm visual analogue scale. Secondary outcomes related to function and disability were also analysed.
Results
The Cardio Zip shoe was selected by 58% of participants. Compared with baseline, overall scores for all shoes at 8-weeks demonstrated a decrease in foot pain (p = 0.03), general pain (p = 0.012), Health Assessment Questionnaire (HAQ)-II (p = 0.016) and Leeds Foot Impact Scale (LFIS) impairment subscale (p = 0.03). No significant differences were observed in other patient reported outcomes including patient global assessment, LFIS activity subscale, and Lower Limb Task Questionnaire subscales (all p > 0.10). We observed significant improvements between baseline measurements using the participants’ own shoes and the Cardio Zip for foot pain (p = 0.002), general pain (p = 0.001), HAQ-II (p = 0.002) and LFIS impairment subscale (p = 0.004) after 8 weeks. The other three shoes did not improve pain or disability.
Conclusions
Footwear with good cushioning, and motion control may reduce foot pain and disability in people with gout.
doi:10.1186/1471-2474-14-278
PMCID: PMC3848939  PMID: 24063678
Gout; Pain; Foot; Disability; Joint; Footwear; Comfort
20.  Association of variation in Fcγ receptor 3B gene copy number with rheumatoid arthritis in Caucasian samples 
Annals of the rheumatic diseases  2010;69(9):1711-1716.
Objective
There is increasing evidence that variation in gene copy number (CN) influences clinical phenotype. The low-affinity Fcγ receptor 3B (FCGR3B) located in the FCGR gene cluster is a CN polymorphic gene involved in the recruitment to sites of inflammation and activation of polymorphonuclear neutrophils (PMNs). Given recent evidence that low FCGR3B CN is a risk factor for systemic but not organ-specific autoimmune disease and the potential importance of PMN in the pathophysiology of rheumatoid arthritis (RA), the authors hypothesised that FCGR3B gene dosage influences susceptibility to RA.
Methods
FCGR3B CN was measured in 643 cases of RA and 461 controls from New Zealand (NZ), with follow-up analysis in 768 cases and 702 controls from the Netherlands and 250 cases and 211 controls from the UK. All subjects were of Caucasian ancestry.
Results
Significant evidence for an association between CN <2 and RA was observed in the Dutch cohort (OR 2.01 (95% CI 1.37 to 2.94), p=3×10–4) but not in the two smaller cohorts (OR 1.45 (95% CI 0.92 to 2.26), p=0.11 and OR 1.33 (95% CI 0.58 to 3.02), p=0.50 for the NZ and UK populations, respectively). The association was evident in a meta-analysis which included a previously published Caucasian sample set (OR 1.67 (95% CI 1.28 to 2.17), p=1.2×10–4).
Conclusions
One possible mechanism to explain the association between reduced FCGR3B CN and RA is the reduced clearance of immune complex during infl ammation. However, it is not known whether the association between RA and FCGR3B CN is aetiological or acts as a proxy marker for another biologically relevant variant. More detailed examination of genetic variation within the FCGR gene cluster is required.
doi:10.1136/ard.2009.123588
PMCID: PMC3670580  PMID: 20472591
24.  Assessment of foot and ankle muscle strength using hand held dynamometry in patients with established rheumatoid arthritis 
Background
The foot and ankle are frequently affected in patients with rheumatoid arthritis (RA). One of the negative consequences of RA on the physical function of patients is a decrease in muscle strength. However, little is known about foot and muscle strength in this population. The aim of the study was to evaluate significant differences in foot and ankle muscle strength between patients with established RA against age and sex-matched controls using hand-held dynamometry.
Methods
The maximal muscle strength of ankle plantarflexion, dorsiflexion, eversion and inversion was assessed in 14 patients with RA, mean (SD) disease duration of 22 (14.1) years, and 20 age and sex-matched control participants using hand-held dynamometry.
Results
Significant differences were observed in muscle strength between the two groups in plantarflexion (p = 0.00), eversion (p = 0.04) and inversion (p = 0.01). No significant difference was found in dorsiflexion (p > 0.05). The patients with RA displayed a significantly lower plantarflexion-dorsiflexion ratio than the control participants (p = 0.03).
Conclusions
The results from this study showed that the RA patients displayed a significant decrease in ankle dorsiflexion, eversion and inversion when compared to the non-RA control group suggesting that foot and ankle muscle strength may be affected by the pathological processes in RA. This study is a preliminary step for the measurement of muscle impairments within the RA population.
doi:10.1186/1757-1146-6-10
PMCID: PMC3614547  PMID: 23522448
25.  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.
doi:10.1186/1471-2474-13-174
PMCID: PMC3493372  PMID: 22978848
Gout; Urate; Target; Allopurinol

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