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1.  Allopurinol treatment and its effect on renal function in gout: a controlled study. 
Fifty-nine patients with primary gout were treated with either a combination of colchicine and allopurinol or colchicine alone. Assessments of renal function over 2 years revealed a statistically significant fall of glomerular filtration rate an urine concentrating ability in those receiving only colchicine. The renal function of patients given allopurinol did not change. Treatment with allopurinol resulted ina significant reduction of ammonium excretion, a phenomenon which could not be readily explained. Urate clearance also declined during allopurinol treatment, and the impaired urate clearance associated with gout became more evident. The most important observation was that allopurinol retarded an apparent decline of renal function. Presumably this was achieved through its hypouricaemic effect and implies that the hyperuricaemia of gouty patients is deleterious to the kidneys.
PMCID: PMC1000865  PMID: 7039523
2.  Reduced Glomerular Function and Prevalence of Gout: NHANES 2009–10 
PLoS ONE  2012;7(11):e50046.
Background
The renal tubule is a major route of clearance of uric acid, a product of purine metabolism. The links between reduced glomerular filtration rate (GFR), hyperuricemia, and gout in the general population are not well understood. The objective of the present study was to estimate prevalence of gout and hyperuricemia among people with impaired GFR in the US general population.
Study Design
Cross-sectional, survey-weighted analyses of data on adults (age>20 years) in the 2009–10 cycle of the US National Health and Nutrition Examination Surveys (n = 5,589). Associations between self-reported physician diagnosis of gout and degrees of renal impairment were the primary focus of the present analyses.
Results
In the 2009–2010 period, there was an estimated 7.5 million people with gout in the US. There were 1.25 million men and 0.78 million women with moderate or severe renal impairment and gout. The age standardized prevalence of gout was 2.9% among those with normal GFR compared to 24% among those with GFR<60 ml/min/1.73 m2.In multivariable logistic regression analyses that adjusted for age, gender, body mass index, hypertension, diabetes, hypertension medications, including diuretics, blood lead levels, and hyperlipidemia, the odds ratios of gout and hyperuricemia were 5.9 (2.2, 15.7) and 9.58 (4.3, 22.0) respectively among those with severe renal impairment compared to those with no renal impairment. Approximately 2–3 fold increase in prevalence of gout was observed for each 30 ml/min/1.73 m2 decrease in GFR, after accounting for the above factors.
Conclusions
Renal glomerular function is an important risk factor for gout. The prevalence of hyperuricemia and gout increases with decreasing glomerular function independent of other factors. This association is non-linear and an eGFR of 60 ml/min/1.73 m2 appears to be a threshold for the dramatic increase in the prevalence of gout.
doi:10.1371/journal.pone.0050046
PMCID: PMC3507834  PMID: 23209642
3.  Serum Cystatin C is a Potential Endogenous Marker for the Estimation of Renal Function in Male Gout Patients with Renal Impairment 
Serum creatinine level is the most commonly used indices for assessment of glomerular filtration rate (GFR), even though these indices have been shown to have some limitations in clinical practice. We investigated the diagnostic efficacy of serum cystatin C compared to that of serum creatinine levels and identified the relating factors associated with changes in serum cystatin C levels in gout patients with renal impairment. A total of 68 gouty patients with renal impairment were enrolled in this study. Diagnostic efficacy of serum cystatin C levels was evaluated through non-parametric receiver operating characteristic (ROC) analysis. The risk factors for changes in serum cystatin C levels were confirmed using multivariate regression analysis. With 24-hr urine creatinine clearance (Ccr) as the reference for GFR, 1/cystatin C (r=0.702, P<0.001) showed a significantly higher correlation with Ccr than 1/creatinine (r=0.665, P<0.001). Multivariate correlation analysis demonstrated that the clinical parameters for increased serum cystatin C are a higher stage of chronic kidney disease, older age, use of allopurinol, and lower high density lipoprotein-cholesterol. The area under the curve (AUC) at ROC plots identified that of serum cystatin C was significantly greater than that of serum creatinine (AUC 0.804 of cystatin C and AUC 0.745 of creatinine). The study suggests that serum cystatin C is a reliable endogenous marker for the assessment of renal function or GFR in gout patients with renal impairment.
doi:10.3346/jkms.2010.25.1.42
PMCID: PMC2800003  PMID: 20052346
Cystatin C; Gout; Creatinine; Kidney Failure; Glomerular Filtration Rate
4.  The Treatment of Gout and Disorders of Uric Acid Metabolism with Allopurinol 
Canadian Medical Association Journal  1966;95(22):1120-1127.
Allopurinol (4-hydroxypyrazolo (3,4-d)-pyrimidine) is a potent xanthine oxidase inhibitor which inhibits the oxidation of naturally occurring oxypurines, thus decreasing uric acid formation. The clinical and metabolic effects of this agent were studied in 80 subjects with primary and secondary gout and other disorders of uric acid metabolism. Allopurinol has been universally successful in lowering the serum uric acid concentration and uric acid excretion to normal levels, while not significantly affecting the clearance of urate or other aspects of renal function. Oxypurine excretion increased concomitantly with the fall in urine uric acid. The agent is particularly valuable in the management of problems of gout with azotemia, acute uric acid nephropathy and uric acid urolithiasis. The minor side effects, clinical indications and theoretical complications are discussed.
PMCID: PMC1935821  PMID: 5923471
5.  A common missense variant of monocarboxylate transporter 9 (MCT9/SLC16A9) gene is associated with renal overload gout, but not with all gout susceptibility 
Human Cell  2013;26(4):133-136.
Gout is a common disease caused by hyperuricemia, which shows elevated serum uric acid (SUA) levels. From a viewpoint of urate handling in humans, gout patients can be divided into those with renal overload (ROL) gout with intestinal urate underexcretion, and those with renal underexcretion (RUE) gout. Recent genome-wide association studies (GWAS) revealed an association between SUA and a variant in human monocarboxylate transporter 9 (MCT9/SLC16A9) gene. Although the function of MCT9 remains unclear, urate is mostly excreted via intestine and kidney where MCT9 expression is observed. In this study, we investigated the relationship between a variant of MCT9 and gout in 545 patients and 1,115 healthy volunteers. A missense variant of MCT9 (K258T), rs2242206, significantly increased the risk of ROL gout (p = 0.012), with odds ratio (OR) of 1.28, although it revealed no significant association with all gout cases (p = 0.10), non-ROL gout cases (p = 0.83), and RUE gout cases (p = 0.34). In any case groups and the control group, minor allele frequencies of rs2242206 were >0.40. Therefore, rs2242206 is a common missense variant and is revealed to have an association with ROL gout, indicating that rs2242206 relates to decreased intestinal urate excretion rather than decreased renal urate excretion. Our study provides clues to better understand the pathophysiology of gout as well as the physiological roles of MCT9.
doi:10.1007/s13577-013-0073-8
PMCID: PMC3844819  PMID: 23990105
Gouty arthritis; Single nucleotide polymorphism (SNP); Gut urate excretion; Carnitine; Solute carrier (SLC) family transporter
6.  African American patients with gout: efficacy and safety of febuxostat vs allopurinol 
Background
African Americans are twice as likely as Caucasians to develop gout, but they are less likely to be treated with urate-lowering therapy (ULT). Furthermore, African Americans typically present with more comorbidities associated with gout, such as hypertension, obesity, and renal impairment. We determined the efficacy and safety of ULT with febuxostat or allopurinol in African American subjects with gout and associated comorbidities and in comparison to Caucasian gout subjects.
Methods
This is a secondary analysis of the 6-month Phase 3 CONFIRMS trial. Eligible gouty subjects with baseline serum urate (sUA) ≥ 8.0 mg/dL were randomized 1:1:1 to receive febuxostat 40 mg, febuxostat 80 mg, or allopurinol (300 mg or 200 mg depending on renal function) daily. All subjects received gout flare prophylaxis. Primary efficacy endpoint was the proportion of subjects in each treatment group with sUA < 6.0 mg/dL at the final visit. Additional endpoints included the proportion of subjects with mild or with moderate renal impairment who achieved a target sUA < 6.0 mg/dL at final visit. Adverse events (AEs) were recorded throughout the study.
Results
Of the 2,269 subjects enrolled, 10.0% were African American and 82.1% were Caucasian. African American subjects were mostly male (89.5%), obese (BMI ≥ 30 kg/m2; 67.1%), with mean baseline sUA of 9.8 mg/dL and mean duration of gout of 10.4 years. The proportions of African American subjects with a baseline history of diabetes, renal impairment, or cardiovascular disease were significantly higher compared to Caucasians (p < 0.001). ULT with febuxostat 80 mg was superior to both febuxostat 40 mg (p < 0.001) and allopurinol (p = 0.004). Febuxostat 40 mg was comparable in efficacy to allopurinol. Significantly more African American subjects with mild or moderate renal impairment achieved sUA < 6.0 mg/dL in the febuxostat 80 group than in either the febuxostat 40 mg or allopurinol group (p < 0.05). Efficacy rates in all treatment groups regardless of renal function were comparable between African American and Caucasian subjects, as were AE rates.
Conclusions
In African American subjects with significant comorbidities, febuxostat 80 mg is significantly more efficacious than either febuxostat 40 mg or allopurinol 200/300 mg. Febuxostat was well tolerated in this African American population.
Please see related article: http://www.biomedcentral.com/1741-7015/10/15
doi:10.1186/1471-2474-13-15
PMCID: PMC3317813  PMID: 22316106
7.  Sugar-sweetened beverage consumption: a risk factor for prevalent gout with SLC2A9 genotype-specific effects on serum urate and risk of gout 
Annals of the Rheumatic Diseases  2013;73(12):2101-2106.
Objective
Consumption of high fructose corn syrup (HFCS)-sweetened beverages increases serum urate and risk of incident gout. Genetic variants in SLC2A9, that exchanges uric acid for glucose and fructose, associate with gout. We tested association between sugar (sucrose)-sweetened beverage (SSB) consumption and prevalent gout. We also tested the hypothesis that SLC2A9 genotype and SSB consumption interact to determine gout risk.
Methods
Participants were 1634 New Zealand (NZ) European Caucasian, Ma¯ori and Pacific Island people and 7075 European Caucasians from the Atherosclerosis Risk in Communities (ARIC) study. NZ samples were genotyped for rs11942223 and ARIC for rs6449173. Effect estimates were multivariate adjusted.
Results
SSB consumption increased gout risk. The OR for four drinks/day relative to zero was 6.89 (p=0.045), 5.19 (p=0.010) and 2.84 (p=0.043) for European Caucasian, Ma¯ori and Pacific Islanders, respectively. With each extra daily SSB serving, carriage of the gout-protective allele of SLC2A9 associated with a 15% increase in risk (p=0.078), compared with a 12% increase in non-carriers (p=0.002). The interaction term was significant in pooled (pInteraction=0.01) but not meta-analysed (pInteraction=0.99) data. In ARIC, with each extra daily serving, a greater increase in serum urate protective allele carriers (0.005 (p=8.7×10−5) compared with 0.002 (p=0.016) mmol/L) supported the gout data (pInteraction=0.062).
Conclusions
Association of SSB consumption with prevalent gout supports reduction of SSB in management. The interaction data suggest that SLC2A9-mediated renal uric acid excretion is physiologically influenced by intake of simple sugars derived from SSB, with SSB exposure negating the gout risk discrimination of SLC2A9.
doi:10.1136/annrheumdis-2013-203600
PMCID: PMC4251167  PMID: 24026676
Gout; Epidemiology; Gene Polymorphism
8.  The effect of febuxostat to prevent a further reduction in renal function of patients with hyperuricemia who have never had gout and are complicated by chronic kidney disease stage 3: study protocol for a multicenter randomized controlled study 
Trials  2014;15:26.
Background
Hyperuricemia is a risk factor for the onset of chronic kidney disease (CKD) and is significantly associated with the progression of CKD. However, there is no sufficient evidence by interventional research supporting a cause-effect relationship. Hyperuricemic patients without gouty arthritis, whose serum urate (SUA) concentration is ≥8.0 mg/dL and who have a complication, are treated by pharmacotherapy in addition to lifestyle guidance. Nevertheless, there is no evidence that rationalizes pharmacotherapy for patients with hyperuricemia who have no complication and whose SUA concentration is below 9.0 mg/dL.
Methods/Design
The FEATHER (FEbuxostat versus placebo rAndomized controlled Trial regarding reduced renal function in patients with Hyperuricemia complicated by chRonic kidney disease stage 3) study is a prospective, multicenter, double-blind, randomized, placebo-controlled trial of febuxostat—a novel, nonpurine, selective, xanthine oxidase inhibitor. The present study will enroll, at 64 medical institutions in Japan, 400 Japanese patients aged 20 years or older who have hyperuricemia without gouty arthritis, who present CKD stage 3, and whose SUA concentration is 7.1-10.0 mg/dL. Patients are randomly assigned to either the febuxostat or the control group, in which febuxostat tablets and placebo are administered orally, respectively. The dosage of the study drugs should be one 10-mg tablet/day at weeks 1 to 4 after study initiation, increased to one 20-mg tablet/day at weeks 5 to 8, and elevated to one 40-mg tablet/day at week 9 and then maintained until week 108. The primary endpoint is estimated glomerular filtration rate (eGFR) slope. The secondary endpoints include the amount and percent rate of change in eGFR from baseline to week 108, the amount and percent rate of change in SUA concentration from baseline to week 108, the proportion of patients who achieved an SUA concentration ≤6.0 mg/dL, and the incidence of renal function deterioration.
Discussion
The present study aims to examine whether febuxostat prevents a further reduction in renal function as assessed with eGFR in subjects and will (1) provide evidence to indicate the inverse association between a reduction in SUA concentration and an improvement in renal function and (2) rationalize pharmacotherapy for subjects and clarify its clinical relevance.
Trial registration
UMIN Identifier: UMIN000008343
doi:10.1186/1745-6215-15-26
PMCID: PMC3899617  PMID: 24433285
Xanthine oxidase inhibitor; Urate-lowering therapy; Reduced renal function; Hyperuricemia; Chronic kidney disease; Randomized controlled study; Placebo
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.  Gout and neurological abnormalities associated with cardiomyopathy in a young man. 
Annals of the Rheumatic Diseases  1990;49(11):942-943.
A 21 year old man with a family history of gout and neurological deficits, developed severe idiopathic congestive cardiomyopathy after a long history of typical gouty attacks and neurological abnormalities. Clinical and laboratory evaluations showed borderline mental retardation, ataxia, sensorineural deafness, marked hyperuricaemia, and excessive uric acid excretion in the presence of impaired renal function. None of the known causes of cardiomyopathy was found. Even though red cell hypoxanthine guanine phosphoribosyltransferase enzyme activity was normal, this case probably represents an inborn error of purine metabolism. The association of cardiomyopathy with gout is very unusual. Previously it has been only once described in a single case.
PMCID: PMC1004270  PMID: 2256745
11.  EULAR evidence based recommendations for gout. Part I: Diagnosis. Report of a task force of the standing committee for international clinical studies including therapeutics (ESCISIT) 
Annals of the Rheumatic Diseases  2006;65(10):1301-1311.
Objective
To develop evidence based recommendations for the diagnosis of gout.
Methods
The multidisciplinary guideline development group comprised 19 rheumatologists and one evidence based medicine expert, representing 13 European countries. Ten key propositions regarding diagnosis were generated using a Delphi consensus approach. Research evidence was searched systematically for each proposition. Wherever possible the sensitivity, specificity, likelihood ratio (LR), and incremental cost‐effectiveness ratio were calculated for diagnostic tests. Relative risk and odds ratios were estimated for risk factors and co‐morbidities associated with gout. The quality of evidence was categorised according to the evidence hierarchy. The strength of recommendation (SOR) was assessed using the EULAR visual analogue and ordinal scales.
Results
10 key propositions were generated though three Delphi rounds including diagnostic topics in clinical manifestations, urate crystal identification, biochemical tests, radiographs, and risk factors/co‐morbidities. Urate crystal identification varies according to symptoms and observer skill but is very likely to be positive in symptomatic gout (LR = 567 (95% confidence interval (CI), 35.5 to 9053)). Classic podagra and presence of tophi have the highest clinical diagnostic value for gout (LR = 30.64 (95% CI, 20.51 to 45.77), and LR = 39.95 (21.06 to 75.79), respectively). Hyperuricaemia is a major risk factor for gout and may be a useful diagnostic marker when defined by the normal range of the local population (LR = 9.74 (7.45 to 12.72)), although some gouty patients may have normal serum uric acid concentrations at the time of investigation. Radiographs have little role in diagnosis, though in late or severe gout radiographic changes of asymmetrical swelling (LR = 4.13 (2.97 to 5.74)) and subcortical cysts without erosion (LR = 6.39 (3.00 to 13.57)) may be useful to differentiate chronic gout from other joint conditions. In addition, risk factors (sex, diuretics, purine‐rich foods, alcohol, lead) and co‐morbidities (cardiovascular diseases, hypertension, diabetes, obesity, and chronic renal failure) are associated with gout. SOR for each proposition varied according to both the research evidence and expert opinion.
Conclusions
10 key recommendations for diagnosis of gout were developed using a combination of research based evidence and expert consensus. The evidence for diagnostic tests, risk factors, and co‐morbidities was evaluated and the strength of recommendation was provided.
doi:10.1136/ard.2006.055251
PMCID: PMC1798330  PMID: 16707533
EULAR; guidelines; gout; diagnosis
12.  Chronic kidney disease in gout in a managed care setting 
BMC Nephrology  2011;12:36.
Background
To study the prevalence of chronic kidney disease (CKD) and its impact on allopurinol dosing and uric acid control among patients with gout.
Methods
This was a retrospective study using data from a large US health plan. Claims and laboratory data were analyzed for enrollees from the health plan database from January 2002 through December 2005. Patients with gout were identified from pharmacy and medical claims data based on the presence of codes for gout medication or gout diagnosis. Severity of CKD was determined using the estimated glomerular filtration rate (eGFR). Allopurinol titration was defined as a change in average daily dose from first prescription to last prescription of ≥ 50 mg.
Results
A total of 3,929 patients were identified for inclusion in this study, 39% of whom had CKD (based on having an eGFR < 90 mL/min/1.73 m2). Subjects with CKD were older (p < 0.01) and more likely to be women (p < 0.01), had a greater number of comorbid conditions (p < 0.01), and were more likely to be prescribed allopurinol (p < 0.01) compared to those with no CKD. The average starting dose of allopurinol was lower among those with CKD, and it decreased with worsening kidney function. Among the 3,122 gout patients who used allopurinol, only 25.6% without CKD and 22.2% with CKD achieved a serum uric acid concentration of < 6.0 mg/dL (p = 0.0409). Also, only 15% of allopurinol users had an upward dose titration (by ≥50 mg), but the average increase in dose did not differ significantly between those with and without CKD.
Conclusions
About two out of every five patients with gout in this population had CKD. Allopurinol doses were not adjusted in the majority of CKD patients. Serum uric acid control in gout was poor among patients without CKD and even worse among those with CKD.
doi:10.1186/1471-2369-12-36
PMCID: PMC3174872  PMID: 21812963
13.  Diuretic induced gout: a multifactorial condition. 
Annals of the Rheumatic Diseases  1992;51(2):259-261.
Fifteen patients with clinical gout occurring after long term treatment with diuretics were studied retrospectively. In all 15 patients one or more additional factors were present which might have contributed to the hyperuricaemia and gout. The most common of these was the impairment of the glomerular filtration rate. Twenty five other patients receiving long term treatment with diuretics who did not have gout were also studied. The concentrations of uric acid, urea, and creatinine were, in general, markedly lower in these patients than in those who had developed gout. It is concluded that diuretic induced gout occurs in patients in whom there is an additional cause of hyperuricaemia, usually impaired renal function.
PMCID: PMC1005670  PMID: 1550414
14.  Association of kidney disease with prevalent gout in the United States in 1988–1994 and 2007–2010☆ 
Objective
To determine the prevalence of gout associated with progressive degrees of kidney disease in the US population.
Methods
We performed a cross-sectional analysis among non-institutionalized adults (age 20 and older) of the National Health and Nutrition Examination Surveys in 1988–1994 and 2007–2010. Gout status was ascertained by self-report of physician-diagnosed gout. Chronic kidney disease (CKD) was defined in stages based on estimated glomerular filtration rate (GFR) and single albuminuria measurements (albumin-to-creatinine ratio). Prevalence ratios comparing successive categories of GFR, albuminuria, and CKD as well as temporal trends over a 22-year interval were determined via Poisson regression.
Results
In the US, the crude prevalence of gout was 2–3% among participants without CKD, 4% among participants with CKD stage 1, 6–10% for stage 2, 11–13% for stage 3, and over 30% for stage 4. The adjusted prevalence ratio comparing the CKD stage 4 stratum to participants without CKD was 3.20 (95% CI: 1.96, 5.24) in 2007–2010 and remained significant even after adjustment for serum uric acid. Notably, there was a statistically significant, progressively greater adjusted prevalence ratio of gout associated with successively lower categories of GFR and higher categories of albuminuria.
Conclusions
Among US adults, there exists a strong dose–response association between impaired renal function and prevalent gout. Health providers should be aware of the elevated burden of gout among patients with CKD especially when evaluating new onset joint pain and swelling.
doi:10.1016/j.semarthrit.2012.09.009
PMCID: PMC3754853  PMID: 23312548
Gout; Chronic kidney disease; Glomerular filtration rate; Albuminuria; NHANES
15.  Blood Coagulation and Platelet Economy in Subjects with Primary Gout 
Canadian Medical Association Journal  1963;89(24):1207-1211.
Previous studies have suggested that there is an increased incidence of degenerative vascular disease in patients with gout and an increased rate of turnover of blood platelets in patients and animals with atherosclerosis. A disturbed uric acid metabolism and “secondary” gout have long been known to occur with bone marrow diseases. A study of platelet economy and blood clotting factors in subjects with primary gout was therefore undertaken.
Twenty-two male subjects with gout but with no clinical evidence of vascular disease were studied. Half of these had a negative family history for vascular disease and half had less fortunate ancestors. The most striking differences were found when gouty patients with a negative family history for vascular disease were compared with similar control subjects. The mean platelet half-life was 2.85 days in the gouty subjects and 3.74 days in the controls. The mean platelet turnover (number/c.mm./day) was 58,750 in gouty subjects, 42,370 in controls. Platelet adhesiveness and plasma thromboplastic activity were correspondingly increased in the gouty subjects. Control subjects with a positive family history all showed relatively active clotting system and platelet turnover, similar to the values found in atherosclerotic subjects. The data indicated that there is increased platelet destruction and production in some patients with primary gout. The relation between this anomaly and the vascular disease, and disturbed urate metabolism in gouty subjects, remains to be investigated.
PMCID: PMC1922159  PMID: 14084698
16.  Allopurinol, Benzbromarone, or a Combination in Treating Patients with Gout: Analysis of a Series of Outpatients 
Objective. To profile a sample of gouty patients treated with allopurinol, benzbromarone, or a combination of these two drugs and to describe the impact of this therapy in reducing uric acid levels. Methods. An observational, transversal study was performed. We evaluated 48 patients diagnosed with gout who were seen at the Outpatient Rheumatology Clinic of the Federal University of Paraná between January 2009 and November 2010. Clinical data, creatinine serum levels, and basal and posttreatment levels of serum urates, transaminases, and bilirubins were recorded. Uric acid levels were measured in a 24-hour urine sample. Patients were divided into three groups: patients given only allopurinol (A), only benzbromarone (B), and both in combined therapy (A + B). Results. The average age of these patients was 56.6 ± 11.4 years, varying from 35 to 81 years. The entire patient group experienced a significant drop in serum urate levels, from 8.5 ± 1.8 mg/dL (0.472 ± 0.1 mmol/L) to 6.7 ± 2.1 mg/dL (0.372 ± 0.116 mmol/L) (P < 0.001), regardless of the prescribed medication. The number of patients taking both drugs whose serum uric acid values fell within normal range (men <7 mg/dL (0.38 mmol/L) and women <6 mg/dL (0.33 mmol/L)) was 85.7% (6/7) while this value for the group taking benzbromarone alone was 75% (3/4) and for the group taking allopurinol alone this number was 51.8% (14/27). Conclusions. The therapeutic combination of benzbromarone and allopurinol significantly decreased serum urate levels in patients with gout when compared to individual use of each of these agents. This finding is especially important in treating patients who cannot control hyperuricemia with monotherapy. Benzbromarone alone or in combination with allopurinol has an important clinical role in controlling hyperuricemia in patients with gout.
doi:10.1155/2014/263720
PMCID: PMC3955622  PMID: 24719620
17.  Tophaceous Gout and Renal Insufficiency: A New Solution for an Old Therapeutic Dilemma 
Case Reports in Medicine  2011;2011:397646.
The prevalence of gout is increasing with increased life expectancy. Approximately half of the patients with gout have some degree of renal impairment. If both conditions persistently coexist, and in severe tophaceous gout, in particular, treatment has been difficult. We here report on the case of an 87-year-old woman, who had been suffering from recurrent gouty arthritis over 4 years. Monthly polyarthritis attacks were accompanied by subcutaneous tophi. Serum uric acid levels were constantly above 600 μmol/L (10 mg/dL). Allopurinol was no option because of intolerance, while benzbromarone was ineffective because of renal impairment. Therefore, the novel xanthin oxidase inhibitor febuxostat was started, achieving rapid control of serum urate levels (<360 μmol/L). After initial worsening of inflammation in the first weeks, gouty attacks stopped and all tophi resolved within the following 10 months. Renal function remained stable.
doi:10.1155/2011/397646
PMCID: PMC3099210  PMID: 21629805
18.  Beneficial effects of weight loss associated with moderate calorie/carbohydrate restriction, and increased proportional intake of protein and unsaturated fat on serum urate and lipoprotein levels in gout: a pilot study 
Annals of the Rheumatic Diseases  2000;59(7):539-543.
OBJECTIVES—Insulin resistance (IR) has been increasingly implicated in the pathogenesis of gout. The lipoprotein abnormalities described in hyperuricaemic subjects are similar to those associated with IR, and insulin influences renal urate excretion. In this study it was investigated whether dietary measures, reported to be beneficial in IR, have serum uric acid (SU) and lipid lowering effects in gout.
METHODS—Thirteen non-diabetic men (median age 50, range 38-62) were enrolled. Each patient had had at least two gouty attacks during the four months before enrolment. Dietary recommendations consisted of calorie restriction to 6690 kJ (1600 kcal) a day with 40% derived from carbohydrate, 30% from protein, and 30% from fat; replacement of refined carbohydrates with complex ones and saturated fats with mono- and polyunsaturated ones. At onset and after 16 weeks, fasting blood samples were taken for determination of SU, serum cholesterol (C), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), and triglycerides (TGs). Results were expressed as median (SD).
RESULTS—At onset, the body mass index (BMI) was 30.5 (8.1) kg/m2. Dietary measures resulted in weight loss of 7.7 (5.4) kg (p=0.002) and a decrease in the frequency of monthly attacks from 2.1 (0.8) to 0.6 (0.7) (p=0.002). The SU decreased from 0.57 (0.10) to 0.47 (0.09) mmol/l (p=0.001) and normalised in 7 (58%) of the 12 patients with an initially raised level. Serum cholesterol decreased from 6.0 (1.7) to 4.7 (0.9) mmol/l (p=0.002), LDL-C from 3.5 (1.2) to 2.7 (0.8) mmol/l (p=0.004), TGs from 4.7 (4.2) to 1.9 (1.0) mmol/l (p=0.001), and C:HDL-C ratios from 6.7 (1.7) to 5.2 (1.0) (p=0.002). HDL-C levels increased insignificantly. High baseline SU, frequency of attacks, total cholesterol, LDL-C and TG levels, and total C:HDL-C ratios correlated with higher decreases in the respective variables upon dietary intervention (p<0.05).
CONCLUSION—The results suggest that weight reduction associated with a change in proportional macronutrient intake, as recently recommended in IR, is beneficial, reducing the SU levels and dyslipidaemia in gout. Current dietary recommendations for gout may need re-evaluation.


doi:10.1136/ard.59.7.539
PMCID: PMC1753185  PMID: 10873964
19.  Metabolic Interactions of Purine Derivatives with Human ABC Transporter ABCG2: Genetic Testing to Assess Gout Risk 
Pharmaceuticals  2013;6(11):1347-1360.
In mammals, excess purine nucleosides are removed from the body by breakdown in the liver and excretion from the kidneys. Uric acid is the end product of purine metabolism in humans. Two-thirds of uric acid in the human body is normally excreted through the kidney, whereas one-third undergoes uricolysis (decomposition of uric acid) in the gut. Elevated serum uric acid levels result in gout and could be a risk factor for cardiovascular disease and diabetes. Recent studies have shown that human ATP-binding cassette transporter ABCG2 plays a role of renal excretion of uric acid. Two non-synonymous single nucleotide polymorphisms (SNPs), i.e., 421C>A (major) and 376C>T (minor), in the ABCG2 gene result in impaired transport activity, owing to ubiquitination-mediated proteosomal degradation and truncation of ABCG2, respectively. These genetic polymorphisms are associated with hyperuricemia and gout. Allele frequencies of those SNPs are significantly higher in Asian populations than they are in African and Caucasian populations. A rapid and isothermal genotyping method has been developed to detect the SNP 421C>A, where one drop of peripheral blood is sufficient for the detection. Development of simple genotyping methods would serve to improve prevention and early therapeutic intervention for high-risk individuals in personalized healthcare.
doi:10.3390/ph6111347
PMCID: PMC3854015  PMID: 24287461
ABC transporter; ABCG2; gout; hyperuricemia; kidney; SNP; uric acid
20.  Chuanhu Anti-Gout Mixture versus Colchicine for Acute Gouty Arthritis: A Randomized, Double-Blind, Double-Dummy, Non-Inferiority Trial 
Background The Chuanhu anti-gout mixture has been used for many years in the treatment of gout in Chinese Traditional Medicine, and current methods for treatments for acute gouty arthritis have been either less effective or have had serious side effects.
Methods In this 12-week, double-blind, double-dummy, non-inferiority study, outpatient individuals with newly diagnosed acute gouty arthritis were randomly assigned to receive Chuanhu anti-gout mixture or colchicine. Both the study investigators and the participants were masked to the treatment assignments. The primary outcome was the recurrence rate of acute gouty arthritis, and the secondary outcomes were changes in white blood cells (WHC) and C-reactive protein (CRP). This trial is registered at ISRCTN.org as trial ISRCTN65219941.
Results A total of 176 patients were randomly assigned to receive either the Chuanhu anti-gout mixture or Colchicine. The overall recurrence rates in the Chuanhu anti-gout mixture group (CH group) and the Colchicine group (Col group) were 12.50% vs 14.77% (difference -2.22%, 95% confidence interval (95% CI): -10.78%~6.23%), meeting the predefined non-inferiority criterion of 15%, as did the data for WHC and CRP. The incidence of adverse events (mainly diarrhea) was less in the Col group than in the CH group (2.27% vs 28.41%, 95% CI 0.01~0.26). In addition, changes in blood uric acid, alanine aminotransferase, aspartate aminotransferase and creatinine in the CH group were significantly larger compared to those in the Col group (P<0.05).
Conclusions The Chuanhu anti-gout mixture was non-inferior to colchicine for the treatment of acute gouty arthritis. The study suggested that the Chuanhu anti-gout mixture can be considered an alternative choice for the treatment of acute gouty arthritis because of its lower incidence of adverse events and its protection of kidney and renal function.
doi:10.7150/ijms.9165
PMCID: PMC4081309  PMID: 25013367
Chuanhu; acute gouty arthritis
21.  Plasma and urinary amino acids in primary gout, with special reference to glutamine 
Journal of Clinical Investigation  1969;48(5):885-894.
Measurement of the plasma free amino acids by column chromatography (AutoAnalyzer) in 32 patients with primary gout showed statistically significant increases or decreases in several components when compared with the spectrum in 18 control subjects, but the absolute amounts involved were small and the mean total plasma amino acid concentrations in both groups were the same. In the urine all major amino acid components, notably glutamine, serine, threonine, and leucine, were lower in our gouty than in our nongouty subjects, as were also the corresponding renal clearance ratios. These deficits could be reproduced by restricting dietary protein, so appear to be due largely to the some-what reduced mean dietary protein intake of our gouty subjects. However, the low renal clearance of glutamine, the most striking and consistent of the deficits in urinary amino acids noted, could not be accounted for by dietary or other relevant factors, and is interpreted as indicating increased tubular reabsorption of glutamine in primary gout. This interpretation was supported by the results of glutamine loading. The possible compensatory relationship of the abnormality in renal handling of glutamine to the deficiency in renal production of ammonia previously reported is discussed.
PMCID: PMC322297  PMID: 5780198
22.  The urate-lowering efficacy and safety of febuxostat in the treatment of the hyperuricemia of gout: the CONFIRMS trial 
Introduction
The purpose of this study was to compare urate-lowering (UL) efficacy and safety of daily febuxostat and allopurinol in subjects with gout and serum urate (sUA) ≥ 8.0 mg/dL in a six-month trial.
Methods
Subjects (n = 2,269) were randomized to febuxostat 40 mg or 80 mg, or allopurinol 300 mg (200 mg in moderate renal impairment). Endpoints included the proportion of all subjects with sUA <6.0 mg/dL and the proportion of subjects with mild/moderate renal impairment and sUA <6.0 mg/dL. Safety assessments included blinded adjudication of each cardiovascular (CV) adverse event (AE) and death.
Results
Comorbidities included: renal impairment (65%); obesity (64%); hyperlipidemia (42%); and hypertension (53%). In febuxostat 40 mg, febuxostat 80 mg, and allopurinol groups, primary endpoint was achieved in 45%, 67%, and 42%, respectively. Febuxostat 40 mg UL was statistically non-inferior to allopurinol, but febuxostat 80 mg was superior to both (P < 0.001). Achievement of target sUA in subjects with renal impairment was also superior with febuxostat 80 mg (72%; P < 0.001) compared with febuxostat 40 mg (50%) or allopurinol (42%), but febuxostat 40 mg showed greater efficacy than allopurinol (P = 0.021). Rates of AEs did not differ across treatment groups. Adjudicated (APTC) CV event rates were 0.0% for febuxostat 40 mg and 0.4% for both febuxostat 80 mg and allopurinol. One death occurred in each febuxostat group and three in the allopurinol group.
Conclusions
Urate-lowering efficacy of febuxostat 80 mg exceeded that of febuxostat 40 mg and allopurinol (300/200 mg), which were comparable. In subjects with mild/moderate renal impairment, both febuxostat doses were more efficacious than allopurinol and equally safe. At the doses tested, safety of febuxostat and allopurinol was comparable.
Clinical Trial Registration
NCT00430248
doi:10.1186/ar2978
PMCID: PMC2888216  PMID: 20370912
23.  Gout disease-specific quality of life and the association with gout characteristics 
Purpose
Assess the association of gout characteristics with health-related quality of life (HRQoL) using a new gout-specific HRQoL instrument, the Gout Impact Scale (GIS).
Patients and methods
Gout patients completed the GIS (five scales [0–100 score each] representing impact of gout overall [three scales] and during an attack [two scales]) and other questions describing recent gout attacks, treatment, gout history, comorbidities, and demographics. Physicians confirmed gout diagnosis, presence of tophi, and most recent serum uric acid (sUA) level. Relationships between gout characteristics and GIS scores were examined using analysis of variance and correlation analyses.
Results
The majority of patients were male (90.2%) with a mean age of 62.2 (±11.8) years. Approximately one-half (49.7%) reported ≥3 gout attacks in the past year and the majority (57.9%) reported experiencing gout-related pain between attacks. Patients had appreciable concern about their gout (“gout concern overall” scale, 63.1 ± 28.0) but believed their treatment was adequate (“unmet gout treatment need” scale (38.2 ± 21.4) below scale mid-point). Significantly worse GIS scores were associated with increasing attack frequency and greater amount of time with pain between attacks (most scales, P < 0.001). Common objective measures such as sUA level, presence of tophi and the number of joints involved in a typical attack did not appear to be good indicators of the impact of gout on the patients' HRQoL.
Conclusion
Attack frequency and gout pain between attacks were important correlates of patients' ratings of gout impact on their HRQoL. Further studies are needed to determine the minimal important difference for each GIS scale and interpret our results relative to other patient populations with gout.
doi:10.2147/PROM.S8310
PMCID: PMC3113652  PMID: 21686040
Gout impact scale; GIS; patient-reported outcomes
24.  Gout disease-specific quality of life and the association with gout characteristics 
Purpose:
Assess the association of gout characteristics with health-related quality of life (HRQoL) using a new gout-specific HRQoL instrument, the Gout Impact Scale (GIS).
Patients and methods:
Gout patients completed the GIS (five scales [0–100 score each] representing impact of gout overall [three scales] and during an attack [two scales]) and other questions describing recent gout attacks, treatment, gout history, comorbidities, and demographics. Physicians confirmed gout diagnosis, presence of tophi, and most recent serum uric acid (sUA) level. Relationships between gout characteristics and GIS scores were examined using analysis of variance and correlation analyses.
Results:
The majority of patients were male (90.2%) with a mean age of 62.2 (±11.8) years. Approximately one-half (49.7%) reported ≥3 gout attacks in the past year and the majority (57.9%) reported experiencing gout-related pain between attacks. Patients had appreciable concern about their gout (“gout concern overall” scale, 63.1 ± 28.0) but believed their treatment was adequate (“unmet gout treatment need” scale (38.2 ± 21.4) below scale mid-point). Significantly worse GIS scores were associated with increasing attack frequency and greater amount of time with pain between attacks (most scales, P < 0.001). Common objective measures such as sUA level, presence of tophi and the number of joints involved in a typical attack did not appear to be good indicators of the impact of gout on the patients’ HRQoL.
Conclusion:
Attack frequency and gout pain between attacks were important correlates of patients’ ratings of gout impact on their HRQoL. Further studies are needed to determine the minimal important difference for each GIS scale and interpret our results relative to other patient populations with gout.
PMCID: PMC3113652  PMID: 21686040
Gout impact scale; GIS; patient-reported outcomes
25.  The efficacy and safety of febuxostat for urate lowering in gout patients ≥65 years of age 
BMC Geriatrics  2012;12:11.
Background
The incidence of gout rises with increasing age. Management of elderly (≥65 years) gout patients can be challenging due to high rates of comorbidities, such as renal impairment and cardiovascular disease, and concomitant medication use. However, there is little data specifically addressing the efficacy and safety of available urate-lowering therapies (ULT) in the elderly. The objective of this post hoc analysis was to examine the efficacy and safety of ULT with febuxostat or allopurinol in a subset of elderly subjects enrolled in the CONFIRMS trial.
Methods
Hyperuricemic (serum urate [sUA] levels ≥ 8.0 mg/dL) gout subjects were enrolled in the 6-month, double-blind, randomized, comparative CONFIRMS trial and randomized, 1:1:1, to receive febuxostat, 40 mg or 80 mg, or allopurinol (200 mg or 300 mg based on renal function) once daily. Flare prophylaxis was provided throughout the study duration.
Study endpoints were the percent of elderly subjects with sUA <6.0 mg/dL at the final visit, overall and by renal function status, percent change in sUA from baseline to final visit, flare rates, and rates of adverse events (AEs).
Results
Of 2,269 subjects enrolled, 374 were elderly. Febuxostat 80 mg was significantly more efficacious (82.0%) than febuxostat 40 mg (61.7%; p < 0.001) or allopurinol (47.3%; p < 0.001) for achieving the primary efficacy endpoint. Febuxostat 40 mg was also superior to allopurinol in this population (p = 0.029). In subjects with mild-to-moderate renal impairment, significantly greater ULT efficacy was observed with febuxostat 40 mg (61.6%; p = 0.028) and febuxostat 80 mg (82.5%; p < 0.001) compared to allopurinol 200/300 mg (46.9%). Compared to allopurinol 200/300 mg, the mean percent change in sUA from baseline was significantly greater for both febuxostat 80 mg (p < 0.001) and febuxostat 40 mg (p = 0.011) groups. Flare rates declined steadily in all treatment groups. Rates of AEs were low and comparable across treatments.
Conclusions
These data suggest that either dose of febuxostat is superior to commonly prescribed fixed doses of allopurinol (200/300 mg) in subjects ≥65 years of age with high rates of renal dysfunction. In addition, in this high-risk population, ULT with either drug was well tolerated.
Trial registration
clinicaltrials.gov NCT#00430248
doi:10.1186/1471-2318-12-11
PMCID: PMC3368715  PMID: 22436129

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