Renal outcomes of gout and hyperuricemia

The Pattern of Allopurinol Prescription Among Chronic Kidney Disease Patients in a Tertiary Care Centre: A Single-Centre Experience

Context

Hyperuricemia is prevalent in patients with chronic kidney disease (CKD). Although it is associated with CKD incidence and progression, treating asymptomatic hyperuricemia with uric acid-lowering agents is still debatable.

Aim of Work

determine the rate of non-classical prescription of allopurinol in CKD patients.

Settings and Design

This was a retrospective study of adult patients prescribed allopurinol with CKD (stages 2–5) in Doctor Soliman Fakeeh Hospital (DSFH) Jeddah, Saudi Arabia, from 1/1/2016 to 1/1/2017.

Subjects and Methods

Eligible patients were identified from the hospital’s pharmacy system and cross-referenced with the electronic health records. Demographic data, laboratory results and indication as recorded by the prescribing physician were extracted. Prescriptions with no indication were categorized based on the uric acid levels. Hyperuricemia was documented as mild (6–10 mg/dL in females and 7–13 mg/dL in males) and severe (>13mg/dL in men and >10mg/dL in women).

Statistical Analysis Used

Descriptive statistics (frequencies, percentages).

Results

From the 594 identified patients, 464 (78.1%) were males. A third of prescriptions (209/594) had no indication, 43.5% of which (91/209) had no documented uric acid levels, and 16.3% (34/209) had normal levels. Including patients with undocumented indication, 64.2% (381/594) were prescribed allopurinol for hyperuricemia, 86.4% of which (329/381) had mild hyperuricemia, and only 13.6% (52/381) had severe hyperuricemia. Other indications included malignancy-related disorders (6.2%, 37/594), gouty arthritis (5.2%, 31/594), and stones of unknown aetiology (3.4%, 20/594).

Conclusion

The percentage of allopurinol prescription to patients with CKD without a clear indication in our centre was markedly high. This might increase the risk for side effects with no evidence-based benefits.

Creation of an adequate animal model of hyperuricemia (acute and chronic hyperuricemia); study of its reversibility and its maintenance

AIM

Hyperuricemia is defined by the European Rheumatology Society as a uric acid level greater than 6 mg/dl (60 mg/l or 360 μmol/l). Our goal was to evaluate the hypouricemic effect of nettle. For this reason, we have first of all try to create an hyperuricemic animal model which is very suitable because at the level of literature there is not an exact model, there are many models and our objective is to set an adequate model.

MATERIALS AND METHODS

An attempt has been made to test acute and chronic hyperuricemia by varying the duration and method of induction of potassium oxonate. Similarly, attempts have been made to induce chronic hyperuricemia through an animal and vegetable diet. The reversibility of hyperuricemia was tested with a maintenance protocol.

KEY FINDINGS

For the creation of the hyperuricemia model, it has been shown that acute hyperuricemia cannot be induced by short administration of potassium oxonate and persistent chronic hyperuricemia can be induced only after daily administration of oxonate of potassium by intraperitoneal injection for 15 days. Indeed, hyperuricemia was reversible after stopping the administration of potassium oxonate. The high-purine diet is also capable of inducing chronic hyperuricemia but to a less extent.

SIGNIFICANCE

After creating an adequate model of hyperuricemia while setting the dose of potassium oxonate, route of administration and duration. A maintenance protocol was followed which subsequently made it possible to deduce that the daily administration of potassium oxonate must be continued to maintain the hyperuricemia.

Hyperuricemia and Impaired Renal Function: A Prospective Cohort Study

Background

Related studies have demonstrated a relationship of elevated serum uric levels with a decline in kidney function. However, limited evidence exists in a Southeast Asian community-based population.

Objective

The study aimed to examine the relationship between serum uric acid levels and impaired renal function.

Methods

A prospective cohort study was conducted in the Thai army health checkup population between July 1, 2006 and December 31, 2012. Inclusion criteria included age older than 20 years and baseline estimated glomerular filtration rate (eGFR) over 60 mL/min/1.73 m². Cox regression analysis was used to evaluate the association between incidence of impaired renal function and baseline serum uric acid quartiles. Impaired renal function was defined as eGFR <60 mL/min/1.73 m² over 3 months.

Results

A total of 9,534 participants (7,474 men and 2,060 women) were enrolled. Cox regression analysis revealed a significant association of serum uric acid level with impaired renal function in the whole population as the unadjusted hazard ratio (HR) (95% CI) of impaired renal function in second, third, and fourth quartiles were 2.1 (1.39, 3.17), 2.39 (1.6, 3.59), and 3.94 (2.71, 5.74), respectively, when compared with serum uric acid in the first quartile, respectively. After adjusting in 2 models, the HR still significantly persisted with similar magnitudes in all quartiles. Higher incidences of impaired renal function were observed among males than among females in all quartiles. Kaplan-Meier curve showed better renal survival rate in the lower quartile groups. Linear regression analysis showed that eGFR negatively correlated with serum uric acid (r = -0.213, p < 0.001).

Conclusion

Our study suggests that an independent association exists of serum uric acid levels with the incidence of impaired renal function and renal progression in the Southeast Asian community-based population.

Effect of Curcumin on Serum Urate in Asymptomatic Hyperuricemia: A Randomized Placebo-Controlled Trial

BACKGROUND/OBJECTIVE

Hyperuricemia leads to gout and renal complications and may increase cardiovascular risk. Curcumin inhibits xanthine oxidase and increases uricosuric activity and, as a result, decreases serum urate (SU). This randomized controlled trial aimed to determine the effects of curcumin versus placebo on SU in subjects with asymptomatic hyperuricemia (SU level ≥ 6 mg/dL in women or ≥ 7 mg/dL in men).

METHODS

Thirty-nine subjects with persistent hyperuricemia were randomized to receive curcumin (500-mg capsules twice daily, 20 subjects) or placebo (19 subjects). Primary outcome was the difference between SU before and 8 weeks after randomization. Secondary outcomes were differences between urine uric acid (UUA) clearance, fasting plasma glucose (FPG), and lipid profiles before and 8 weeks after randomization and adverse events.

RESULTS

Out of 39 subjects, there were no differences at baseline SU, UUA clearance, FPG, lipid profiles, and demographics between curcumin and placebo groups. After 8 weeks, SU was significantly decreased in both groups (6.9% in curcumin group, p = 0.002, and 5.0% in placebo group, p = 0.009). However, there was no difference in SU reduction between the two groups (p = 0.532). There were no differences in UUA, FPG, lipid profiles, or adverse events in either group at 8 weeks after randomization. The most common adverse event was diarrhea with no treatment required.

CONCLUSION

Curcumin was not superior to placebo in reducing serum urate and in increasing UUA clearance.

Management of asymptomatic hyperuricemia: Integrated Diabetes & Endocrine Academy (IDEA) consensus statement

AIM

The definition and management of asymptomatic hyperuricemia has been an area of controversy for many decades. Debate persists regarding the benefit of treating all cases of asymptomatic hyperuricemia and hence, unsurprisingly there are no clear clinical practice guidelines from our country.

PARTICIPANTS

Ten members consisting of eminent physicians, endocrinologists, nephrologist and a rheumatologist were selected by the Integrated Diabetes & Endocrine Academy (IDEA) for a closed meeting with the aim to come to a consensus.

EVIDENCE

A literature search was performed using PubMed and Cochrane library following which published articles in indexed peer review journals were selected.

CONSENSUS PROCESS

Each participant voiced their opinion after reviewing the available data and a consensus was reached after three meetings by voting.

CONCLUSION

Recommendations were made on important areas such as definition, investigation and management of asymptomatic hyperuricemia.

Association between serum uric acid and chronic kidney disease in patients with hypertension: A multicenter nationwide cross-sectional study

INTRODUCTION

Current data on the role of hyperuricemia as a risk factor for renal progression in patients with hypertension is inconclusive. This study aimed to assess the association of uric acid and chronic kidney disease (CKD) in hypertensive patients using a nationwide patient sample.

METHODS

We conducted a nationwide cross-sectional study based on the DM/HT study of the Medical Research Network of the Consortium of Thai Medical Schools. This study evaluated adult patients with hypertension from 831 Thailand public hospitals in the year 2014. Serum uric acid (SUA) was categorized into quintiles (≤4.5, 4.6 to 5.4, 5.5 to 6.2, 6.3 to 7.4, ≥7.5 mg/dL). CKD was defined as estimated glomerular filtration rate of ≤ 60 mL/min/1.73 m² . Multivariate logistic regression was performed to assess the association between SUA and CKD using uric acid of ≤4.5 mg/dL as the reference group.

RESULTS

A total of 9776 hypertensive patients with available SUA were included in the analysis. The mean SUA was 6.1±1.8 mg/dL. The prevalence of CKD in hypertensive patients was 31.8%. SUA of 4.6 to 5.4, 5.5 to 6.2, 6.3 to 7.4, and ≥7.5 mg/dL were associated with an increased CKD with ORs of 1.57 (95% CI 1.28 to 1.92), 2.15 (95% CI 1.74 to 2.66), 3.31 (95% CI 2.72 to 4.04), and 7.11 (95% CI 5.76 to 8.78), respectively. The restricted cubic spline showed significant increased CKD prevalence when uric acid ≥4.6 mg/dL.

CONCLUSION

Higher SUA was associated with increased CKD prevalence in patients with hypertension. SUA should be monitored in hypertensive patients for CKD prevention.

The case for uric acid-lowering treatment in patients with hyperuricaemia and CKD

Hyperuricaemia is common among patients with chronic kidney disease (CKD), and increases in severity with the deterioration of kidney function. Although existing guidelines for CKD management do not recommend testing for or treatment of hyperuricaemia in the absence of a diagnosis of gout or urate nephrolithiasis, an emerging body of evidence supports a direct causal relationship between serum urate levels and the development of CKD. Here, we review randomized clinical trials that have evaluated the effect of urate-lowering therapy (ULT) on the rate of CKD progression. Among trials in which individuals in the control arm experienced progressive deterioration of kidney function (which we define as ≥4 ml/min/1.73 m² over the course of the study - typically 6 months to 2 years), treatment with ULT conferred consistent clinical benefits. In contrast, among trials where clinical progression was not observed in the control arm, treatment with ULT was ineffective, but this finding should not be used as an argument against the use of uric acid-lowering therapy. Although additional studies are needed to identify threshold values of serum urate for treatment initiation and to confirm optimal target levels, we believe that sufficient evidence exists to recommend routine measurement of serum urate levels in patients with CKD and consider initiation of ULT among those who are hyperuricaemic with evidence of deteriorating renal function, unless specific contraindications exist.

Gout is associated with a higher risk of chronic renal disease in older adults: a retrospective cohort study of U.S. Medicare population

Background

Hyperuricemia and gout have been linked to chronic kidney disease (CKD). Whether the increased risk of CKD in gout is due to shared risk factors such as hypertension, diabetes or heart disease, or due to gout itself is not known. Studies in older adults, who tend to have a high incidence of CKD, are limited. Our objective was to assess whether gout was associated with incident CKD in older adults.

Methods

Using the 5% random sample of Medicare claims, we assessed whether gout is associated with higher risk of incident (new) CKD in adults 65 years or older, using multivariable-adjusted Cox regression analyses, adjusting for demographics (age, gender, race), medical comorbidity and common medications. We calculated hazard ratios (HR) and 95% confidence interval (CI). Sensitivity analyses varied comorbidity variable (models 2, 3), or limited CKD to the most specific codes.

Results

Of the 1,699,613 eligible people, 168,065 developed incident CKD; 150,162 people without gout and 17,903 people with gout. Respective crude incidence rates were 15.6 vs. 78.1 per 1000 person-years. We found that gout was associated with a higher risk of incident CKD in multivariable-adjusted analyses, HR was 3.05 (95% CI, 2.99, 3.10), with minimal attenuation in sensitivity analyses, with HR 2.96 (95% CI, 2.91, 3.01) (model 2, categorical Charlson-Romano) and 2.59 (95% CI, 2.54, 2.63) (model 3, individual Charlson-Romano comorbidities plus hypertension, heart disease, obesity, coronary artery disease). Sensitivity analyses that limited the CKD diagnostic codes to more specific codes, confirmed findings from the main models with respective HRs of 3.10 (95% CI, 3.05, 3.15; Model 1), 3.03 (95% CI, 2.97, 3.08; Model 2) and 2.60 (95% CI, 2.56, 2.65; Model 3).

Conclusion

Gout was associated with a 3-fold higher risk of CKD, confirmed in multiple sensitivity analyses. Future studies should provide insights into underlying mechanisms that are responsible for an increased CKD risk in gout.

Insulin resistance is an independent predictor of erectile dysfunction in patients with gout

BACKGROUND/AIMS

Gout is associated with metabolic disorders that are important risk factors for cardiovascular disease and erectile dysfunction (ED). We aimed to identify independent predictors of ED in patients with gout.

METHODS

From August 2014 to August 2015, male outpatients who were being treated for gout in our rheumatology clinic and healthy males without any history of inflammatory disease (control group) were studied. ED was assessed in participants using the five-item version of the International Index of Erectile Function questionnaire. Insulin resistance (IR) was estimated using the homeostatic model assessment (HOMA-IR). Logistic regression analysis was performed to determine the effect of variables on ED risk in all of the study subjects and in patients with gout.

RESULTS

We analyzed 80 patients with gout and 70 healthy controls. The median age of patients with gout was 52 years and median disease duration was 120 months. Gout patients were more likely to have ED than controls (55.3% vs. 41.4%, p < 0.047). After adjustment for confounding factors, only HOMA-IR was significantly associated with ED (odds ratio [OR], 1.82; 95% confidence interval [CI], 1.05 to 3.15). Gout patients with ED were more likely to be older (p < 0.001), have higher HOMA-IR (p = 0.048), and have lower glomerular filtration rate (p = 0.038) than those without ED. Multivariate logistic regression analysis showed that HOMAIR was an independent predictor for ED (OR, 1.62; 95% CI, 1.03 to 2.82) in gout patients.

CONCLUSION

IR is an independent predictor of ED in patients with gout.

Characteristics of gout patients according to the laterality of nephrolithiasis: A cross-sectional study using helical computed tomography

Objective

To clarify the clinical and laboratory characteristics of nephrolithiasis in gout by computed tomography (CT).

Methods

In 350 gout patients, unenhanced CT was performed at the 1st visit to hospital. Calculus density spots exceeding 1 mm in diameter with a CT value >120 Hounsfield units in the kidneys were defined as kidney stones. The association between laterality and the number of stones was investigated in each stone carrier. The 350 patients were classified into three groups (bilateral, unilateral and non‐stone carriers). Then serum urate (Sua), renal function, uric acid metabolism, and the prevalence of metabolic syndrome (Mets) were compared among these groups by the Tukey‐Kramer test or Fisher's exact test.

Results

Kidney stone(s) were detected in 108 (31%) of the 350 patients (bilateral in 58 and unilateral in 50). In 64 of the 108 patients (59%), there was no history of urolithiasis. Sua, serum creatinine and uric acid clearance were significantly higher (P = 0.001, P < 0.001, P = 0.043, respectively), while the estimated glomerular filtration rate was significantly lower (P = 0.039) in bilateral stone carriers than in non‐stone carriers. No significant differences of uric acid metabolism or the prevalence of Mets were noted among the three groups.

Conclusions

Approximately one‐third of gout patients had kidney stones and more than half of the patients with stones were bilateral and multiple stone carriers. Elevation of Sua might increase the stone burden in gout, leading to more severe renal dysfunction. An association between nephrolithiasis and Mets was not demonstrated in gout patients.

Risk of chronic kidney disease in patients with gout and the impact of urate lowering therapy: a population-based cohort study

Background

An association between gout and renal disease is well-recognised but few studies have examined whether gout is a risk factor for subsequent chronic kidney disease (CKD). Additionally, the impact of urate-lowering therapy (ULT) on development of CKD in gout is unclear. The objective of this study was to quantify the risk of CKD stage ≥ 3 in people with gout and the impact of ULT.

Methods

This was a retrospective cohort study using data from the Clinical Practice Research Datalink (CPRD). Patients with incident gout were identified from general practice medical records between 1998 and 2016 and randomly matched 1:1 to patients without a diagnosis of gout based on age, gender, available follow-up time and practice. Primary outcome was development of CKD stage ≥ 3 based on estimated glomerular filtration rate (eGFR) or recorded diagnosis. Absolute rates (ARs) and adjusted hazard ratios (HRs) were calculated using Cox regression models. Risk of developing CKD was assessed among those prescribed ULT within 1 and 3 years of gout diagnosis.

Results

Patients with incident gout (n = 41,446) were matched to patients without gout. Development of CKD stage ≥ 3 was greater in the exposed group than in the unexposed group (AR 28.6 versus 15.8 per 10,000 person-years). Gout was associated with an increased risk of incident CKD (adjusted HR 1.78 95% CI 1.70 to 1.85). Those exposed to ULT had a greater risk of incident CKD, but following adjustment this was attenuated to non-significance in all analyses (except on 3-year analysis of women (adjusted HR 1.31 95% CI 1.09 to 1.59)).

Conclusions

This study has demonstrated gout to be a risk factor for incident CKD stage ≥ 3. Further research examining the mechanisms by which gout may increase risk of CKD and whether optimal use of ULT can reduce the risk or progression of CKD in gout is suggested.

Electronic supplementary material

The online version of this article (10.1186/s13075-018-1746-1) contains supplementary material, which is available to authorized users.

Asymptomatic hyperuricemia: is it time to intervene?

Whether to treat hyperuricemia uncomplicated by articular gout, urolithiasis, or uric acid nephropathy is an exercise in clinical judgment and universal agreement is lacking. Patients with coronary artery disease, chronic kidney disease, and early onset hypertension with persistent hyperuricemia are likely to be benefited with urate-lowering therapy. The paradigm of the causative association of hyperuricemia with cardiovascular and chronic kidney diseases seems to have progressed from skepticism to increasing evidence of a true relationship. Although such evidences are mounting, they are not enough to support pharmacotherapy for all patients with asymptomatic hyperuricemia. Further studies are needed to determine which patients are likely to get beneficial effects from pharmacotherapy and the minimum threshold of uric acid level required to experience clinical benefits.

Uric acid in the pathogenesis of metabolic, renal, and cardiovascular diseases: A review

The association between uric acid (UA) on one side and systemic hypertension (Htn), dyslipidemia, glucose intolerance, overweight, fatty liver, renal disease and cardiovascular disease (CVD) on the other side is well recognized. However, the causal relationship between UA and these different clinical problems is still debatable. The recent years have witnessed hundreds of experimental and clinical trials that favored the opinion that UA is a probable player in the pathogenesis of these disease entities. These studies disclosed the strong association between hyperuricemia and metabolic syndrome (MS), obesity, Htn, type 2 diabetes mellitus (DM), non-alcoholic fatty liver disease, hypertriglyceridemia, acute kidney injury, chronic kidney disease (CKD), coronary heart disease (CHD), heart failure and increased mortality among cardiac and CKD patients. The association between UA and nephrolithiasis or preeclampsia is a non-debatable association. Recent experimental trials have disclosed different changes in enzyme activities induced by UA. Nitric oxide (NO) synthase, adenosine monophosphate kinase (AMPK), adenosine monophosphate dehydrogenase (AMPD), and nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase are affected by UA. These changes in enzymatic activities can lead to the observed biochemical and pathological changes associated with UA. The recent experimental, clinical, interventional, and epidemiologic trials favor the concept of a causative role of UA in the pathogenesis of MS, renal, and CVDs.

Comparative effectiveness of allopurinol versus febuxostat for preventing incident renal disease in older adults: an analysis of Medicare claims data

OBJECTIVE

To assess the comparative effectiveness of allopurinol versus febuxostat for preventing incident renal disease in elderly.

METHODS

In a retrospective cohort study using 2006-2012 Medicare claims data, we included patients newly treated with allopurinol or febuxostat (baseline period of 183 days without either medication). We used 5:1 propensity-matched Cox regression analyses to compare the HR of incident renal disease with allopurinol use (and dose) versus febuxostat (reference). Sensitivity analyses included multivariable-adjusted regression models.

RESULTS

There were 31 465 new allopurinol or febuxostat treatment episodes in 26 443 patients; 8570 ended in incident renal disease. Crude rates of incident renal disease per 1000 person-years were 192 with allopurinol versus 338 with febuxostat. Crude rates of incident renal disease per 1000 person-years were lower with higher daily dose: allopurinol <200, 200-299 and ≥300 mg/day with 238, 176 and 155; and febuxostat 40 and 80 mg/day with 341 and 326, respectively. In propensity-matched analyses, compared with febuxostat, allopurinol use was associated with lower HR of incident renal disease, 0.61 (95% CI 0.49 to 0.77). Compared with febuxostat 40 mg/day, allopurinol doses <200, 200-299 and ≥300 mg/day were associated with lower HR of incident renal disease, 0.75 (95% CI 0.65 to 0.86), 0.61 (95% CI 0.52 to 0.73) and 0.48 (95% CI 0.41 to 0.55), respectively. Sensitivity analyses using multivariable-adjusted regression confirmed these findings.

CONCLUSIONS

Allopurinol was associated with a lower risk of incident renal disease in elderly patients than febuxostat. Future studies need to examine the mechanism of this potential renal benefit of allopurinol.

Treating Gout in Kidney Transplant Recipients

Objective

To review the etiology, treatment, and preventive strategies of hyperuricemia and gout in kidney transplant recipients.

Data Sources

Primary literature was obtained via Medline (1966-June 2003).

Study Selection and Data Extraction

Studies evaluating treatment and prevention of hyperuricemia and gout in kidney transplantation were considered for evaluation. English-language studies were selected for inclusion.

Data Synthesis

Approximately 14000 kidney transplantations were performed in the United States in 2003, and of those transplant recipients, nearly 13% will experience a new onset of gout. The prevalence of hyperuricemia is even greater. There are several mechanisms by which hyperuricemia and gout develop in kidney transplant recipients. Medication-induced hyperuricemia and renal dysfunction are 2 of the more common mechanisms. Prophylactic and treatment options include allopurinol, colchi cine, corticosteroids, and, if absolutely necessary, nonsteroidal anti-inflammatory drugs.

Conclusion

It is generally recommended to decide whether the risks of prophylactic therapy and treatment outweigh the benefits. Often, the risk of adverse events associated with agents to treat these ailments tends to outweigh the benefits; therefore, treatment is usually reserved for symptomatic episodes of acute gout. Practitioners must also decide if changes in immunosuppressive regimens may be of benefit on a patient-by-patient basis.

Serum uric acid and the incidence of CKD and hypertension

Background

Uric acid (UA) levels correlate positively with the prevalence of chronic kidney disease (CKD) and/or hypertension. We tested the hypothesis that UA may also have a link to a new incidence of CKD and hypertension.

Methods

Study design is a cohort study and the predictor is UA levels. Of the 15,470 screened cases, 8223 participants without CKD were eligible for the analysis of the incidence of CKD. Among these CKD candidates, 7569 participants were eligible for the analysis of the new development of hypertension. The observation period was 4 years.

Results

Relationship of UA with new cases of CKD. Higher UA levels had a closer association with the new development of CKD; 1.1 % (UA < 5 mg/dL), 1.5 % (5.0–5.9 mg/dL), 1.7 % (6.0–6.9 mg/dL), and 3.4 % (≧7 mg/dL), respectively (p < 0.001 by the Chi-square test). Cox proportional hazard analysis showed that the estimates of the CKD development were eGFR [Hazard Ratio (HR) 0.816, 95 % confidence intervals (CI) 0.791–0.840] and male gender (HR 0.562, 95 % CI 0.322–0.982). UA levels and new development of hypertension. Higher UA levels had a closer association with the new development of hypertension; 5.0 % (UA < 5 mg/dL), 8.9 % (5.0–5.9 mg/dL), 10.6 % (6.0–6.9 mg/dL), and 11.8 % (≧7 mg/dL), respectively (p < 0.001 by the Chi-square test). Cox proportional hazard analysis showed that the estimates of the hypertension development were BMI (HR 1.190, 95 % CI 1.155–1.226), age (HR 1.021, 95 % CI 1.010–1.032), HDL-cholesterol (HR 1.013, 95 % CI 1.007–1.019), male gender (HR 1.791, 95 % CI 1.338–2.395), UA level (HR 1.112, 95 % CI 1.024–1.207), and eGFR (HR 1008, 95 % CI 1.002–1.013). Furthermore, the logistic analysis showed that the odds ratio (OR) to estimate hypertension in the high UA group (UA ≧ 7 mg/dL; OR 1.33, 95 % CI 1.01–1.80) was greater than that in the low UA group (UA < 5 mg/dL). Kaplan–Meier analysis also confirmed the finding that the higher the UA levels the greater the hypertension development (p < 0.001 by the Log-rank test and Cox proportional hazard analysis).

Conclusion

High UA levels are associated with the new development of hypertension, but not with the incidence of CKD.

Gout and risk of chronic kidney disease and nephrolithiasis: meta-analysis of observational studies

Introduction

To determine the prevalence of chronic kidney disease and nephrolithiasis in people with gout, and the association between gout and prevalent or incident chronic kidney disease and nephrolithiasis.

Methods

Systematic review and meta-analysis of epidemiological studies. Data sources; MEDLINE, EMBASE and CINAHL databases, hand-searched reference lists, citation history and contact with authors. Eligibility criteria: cohort, case–control or cross-sectional studies which examined the occurrence of chronic kidney disease or nephrolithiasis amongst adults with gout (with or without a non-gout comparator group) in primary care or general population samples. Prevalence and risk estimate meta-analyses were performed using a random-effects model.

Results

Seventeen studies were included in the meta-analysis (chronic kidney disease n = 7, nephrolithiasis n = 8, both n = 2). Pooled prevalence estimates of chronic kidney disease stage ≥3 and self-reported lifetime nephrolithiasis in people with gout were 24% (95% confidence interval 19% to 28%) and 14% (95% CI 12% to 17%) respectively. Gout was associated with both chronic kidney disease (pooled adjusted odds ratio 2.41, 95% confidence interval 1.86 to 3.11) and self-reported lifetime nephrolithiasis (1.77, 1.43 to 2.19).

Conclusions

Chronic kidney disease and nephrolithiasis are commonly found amongst patients with gout. Gout is independently associated with both chronic kidney disease and nephrolithiasis. Patients with gout should be actively screened for chronic kidney disease and its consequences.

Epidemiology of gout

Gout is the most prevalent inflammatory arthritis in men. The findings of several epidemiologic studies from a diverse range of countries suggest that the prevalence of gout has risen over the past few decades. Although incidence data are scarce, data from the United States suggests that the incidence of gout is also rising. Evidence from prospective epidemiologic studies has confirmed dietary factors (animal purines, alcohol, and fructose), obesity, the metabolic syndrome, hypertension, diuretic use, and chronic kidney disease as clinically relevant risk factors for hyperuricemia and gout. Low-fat dairy products, coffee, and vitamin C seem to have a protective effect.

Serum uric acid and the risk of mortality during 23 years follow-up in the Scottish Heart Health Extended Cohort Study

BACKGROUND

Elevated uric acid is a prevalent condition with controversial health consequences. Observational studies disagree with regard to the relationship of uric acid with mortality, and with factors modifying this relationship.

OBJECTIVE

We examined the association of serum uric acid with mortality in 15,083 participants in the Scottish Heart Health Extended Cohort (SHHEC) Study.

METHODS

Serum uric acid was measured at study enrollment. Death was ascertained using both the Scottish death register and record linkage.

RESULTS

During a median follow-up of 23 years, there were 3980 deaths. In Cox proportional hazards models with sexes combined, those in the highest fifth of uric acid had significantly greater mortality (HR 1.18, 95% CI: 1.06, 1.31) compared with the second fifth, after adjustment for traditional cardiovascular risk factors. This relationship was modified by sex (P-interaction=0.002) with adjusted HRs of 1.69 (95% CI: 1.40, 2.04) and 0.99 (95% CI: 0.86, 1.14) in women and men, respectively. Compared with the second fifth, the highest fifth of uric acid was most associated with kidney-related death (HR: 2.08, 95% CI: 1.31, 3.32).

CONCLUSION

Elevated uric acid is associated with earlier mortality, especially in women. Future studies should evaluate mechanisms for these interactions and explore the strong association with renal-related mortality.

Allopurinol for prevention of progression of kidney disease with hyperuricemia

Hyperuricemia is associated with hypertension and progressive chronic renal disease. This is a retrospective cohort study in chronic kidney disease (CKD) patients with hyperuricemia from 1998 to 2008. Patients were divided into two groups: treatment group who received allopurinol in a dose of 100 mg/day and the other group remained untreated. Clinical, hematologic, biochemical parameters and outcome were measured at baseline and 6 months, 1 year, and 2 years of treatment. A total of 183 patients were enrolled. Mean age of the allopurinol group was 50.15 ± 14.42 years and control group was 53.23 ± 13.86 years. Male-female ratios were 2.57:1 and 2.21:1 for the treatment and control groups, respectively. Baseline characteristics and the laboratory parameters were similar in both groups. Patients who received allopurinol had lower blood pressure at 6 months, 1 year, and 2 years when compared to baseline. There was a significant decrease in the serum uric acid (UA) levels in the treatment group at the end of 6 months, 1 year, and 2 years with respect to base line. An inverse correlation as noted between serum UA levels and the estimated glomerular filtration rate at 6 months, 1 year, and 2 years. Allopurinol treatment decreases blood UA levels and is associated with better blood pressure control and decreased progression of renal disease in CKD patients with hyperuricemia.

Novel evaluation of nephrolithiasis as a complication of gout: a cross-sectional study using helical computerized tomography

PURPOSE

We clarified whether the clinical profiles of patients with a history of urolithiasis (stone formers) truly reflect those of patients who currently have renal stones (stone carriers).

MATERIALS AND METHODS

We evaluated 463 patients with gout using helical computerized tomography, urolithiasis history and relevant clinical parameters.

RESULTS

Nephrolithiasis was observed in 157 of the 463 patients (34%) on helical computerized tomography but only 75 (16%) had a urolithiasis history. Of the 157 stone carriers 107 (68%) did not have a urolithiasis history. In those 157 patients serum urate and serum creatinine were higher than in the 306 nonstone carriers (p = 0.017), and the estimated glomerular filtration rate and urinary pH were lower (p = 0.0096 and 0.0249, respectively). However, there was no significant difference in laboratory findings between the 75 stone formers and 388 nonstone formers. Serum urate and creatinine were higher, and the estimated glomerular filtration rate and urine pH in bilateral stone carriers were lower than in unilateral stone carriers. According to HU density attenuation values on computerized tomography, an estimated third of the calculi that complicated 31 recent gout cases was uric acid.

CONCLUSIONS

The concept of stone formers may lead to underestimating the prevalence of urolithiasis. Our analysis of stone carriers showed that a higher stone burden is associated with greater renal derangement, as determined by serum urate and creatinine, the estimated glomerular filtration rate and urine pH. To accurately clarify the correlation of gout and urolithiasis, it is advantageous to select stone carriers as subjects of study.

Gout, stone composition and urinary stone risk: a matched case comparative study

PURPOSE

We established the most common stone composition, and serum and urinary biochemical features in patients with gout and urolithiasis.

MATERIALS AND METHODS

We retrospectively searched for the records of patients diagnosed with gout among all those in our stone registry. A matched case cohort of stone formers was generated from our registry who had the same age, gender and body mass index. Primary end points were baseline 24-hour urinary metabolic panels and stone composition. Medications were considered. Groups were compared using the Student t and chi-square/Fisher exact tests with significance considered at p <0.05.

RESULTS

For stone panel evaluation 181 patients met our inclusion criteria. There was no significant difference in 24-hour uric acid between the nongout and gout cohorts but hyperoxaluria was more common in patients with gout (74% vs 61%, p = 0.009). For stone composition analysis 393 patients were included. The gout cohort had lower calcium oxalate monohydrate (39.4% vs 54.7%), calcium oxalate dihydrate (6.0% vs 11.2%) and calcium phosphate (9.6% vs 14.1%) but higher uric acid (42.7% vs 18.2%, each p <0.001). Pure uric acid stones were more common in patients with gout (52.2% vs 22.3%, p <0.001), while calcium oxalate monohydrate (45.2% vs 68.6%, p <0.001), calcium oxalate dihydrate (0.6% vs 3.5%, p = 0.017) and calcium phosphate (1.6% vs 4.9%, p = 0.033) were more common in nongout cases. Patients with gout who were on allopurinol had fewer pure uric acid stones (30.4% vs 56.4%) and more calcium oxalate monohydrate stones (69.6% vs 40.7%, each p <0.001) than those without medication.

CONCLUSIONS

Uric acid stones are the most common pure stone composition in patients with gout but 48% have nonuric acid stones. Allopurinol changes the stone composition distribution in patients with gout to a pattern similar to that in stone formers without gout.

Uric acid levels predict future development of chronic kidney disease

AIMS

Increased uric acid levels are associated with kidney dysfunction. We tested the hypothesis that uric acid level predicts future development of chronic kidney disease (CKD) in the general population.

METHODS

For this study, we enrolled 7,078 consecutive subjects with normal estimated glomerular filtration rates (eGFR; ≥60 ml/min/1.73 m(2)) who visited our hospital for a yearly health checkup (age: 52.8 ± 10.7 years; female: 35.8%). Subjects underwent a routine physical examination and laboratory assessment of cardiovascular disease risk factors at enrollment, and were followed up for 1,694 days (median) with the endpoint being the development of CKD (eGFR <60 ml/min/1.73 m(2)). The impact of uric acid and other cardiovascular risk factors at baseline on the future development of CKD were assessed.

RESULTS

During the follow-up period, 417 male (9.2%) and 151 female subjects (6.0%) developed CKD. Univariate logistic regression analysis revealed a significant association between the onset of CKD and age, male gender, body mass index, blood pressure, fasting plasma glucose, dyslipidemia and uric acid. Multiple logistic regression analysis revealed that new-onset CKD was independently correlated with the baseline uric acid level after adjustment for possible factors. Subanalysis showed similar results in subjects with normal uric acid levels (male: ≤7.0 mg/dl; female: ≤6.0 mg/dl; n = 6,223).

CONCLUSION

Uric acid is an independent predictor of future development of CKD. Whether preventing an increase in uric acid levels reduces the incidence of CKD must be clarified by prospective follow-up studies.

New and improved strategies for the treatment of gout

The Western world appears to be in the midst of the third great gout epidemic of all time. In this century, gout is increasing in prevalence despite an increased understanding of its risk factors and pathophysiology, and the availability of reasonably effective treatment. The main cultural factors responsible for this appear to be diet, obesity, ethanol use and medications. Excess fructose consumption is a newly recognized modifiable risk factor. The debate has been renewed concerning hyperuricemia as an independent risk factor for renal insufficiency and cardiovascular disease. Prevention is still rooted in lifestyle choices. Existing treatments have proven to be unsatisfactory in many patients with comorbidities. New treatments are available today and on the horizon for tomorrow, which offer a better quality of life for gout sufferers. These include febuxostat, a nonpurine inhibitor of xanthine oxidase with a potentially better combination of efficacy and safety than allopurinol, and investigational inhibitors of URAT-1, an anion exchanger in the proximal tubule that is critical for uric acid homeostasis. New abortive treatments include interleukin-1 antagonists that can cut short the acute attack in 1 to 2 days in persons who cannot take nonsteroidal anti-inflammatory drugs, colchicine or corticosteroids. Lastly, newer formulations of uricase have the ability to dissolve destructive tophi over weeks or months in patients who cannot use currently available hypouricemic agents. Diagnostically, ultrasound and magnetic resonance imaging offer advanced ways to diagnose gout noninvasively, and just as importantly, a way to follow the progress of tophus dissolution. The close association of hyperuricemia with metabolic syndrome, hypertension and renal insufficiency ensures that nephrologists will see increasing numbers of gout-afflicted patients.

Hyperuricaemia and accelerated reduction in renal function

OBJECTIVES

Hyperuricaemia has been linked to reduced renal function, and evidence indicates that it may be associated with acceleration of the decline in glomerular filtration rate (GFR) and progression of chronic kidney disease (CKD).

METHODS

We analysed a population of subjects who had undergone serum uric acid (SUA) and serum creatinine measurements in a hospital-based cohort. Initial and final serum creatinine measurements were used to calculate the estimated glomerular filtration rate (eGFR) and the annual decline in eGFR. Cox regression was used to investigate the relationship between SUA and CKD progression.

RESULTS

A total of 63,785 subjects were enrolled in the study during a 12-year follow-up period. The mean age at the time of initial serum creatinine measurement was 50.0 ± 14.9 years. Hyperuricaemic subjects had a significantly larger annual eGFR decline, both in absolute terms (2.5 ± 9.5 mL/min/1.73 m(2) per year) and as a percentage (2.8 ± 11.6% per year), as compared to the normouricaemia group (1.3 ± 9.6 mL/min/1.73 m(2) per year, 1.1 ± 11.1% per year, p < 0.001). After adjustment for age, sex, status of diabetes mellitus (DM) and hypertension, baseline eGFR, azotaemia, hypercholesterolaemia, and hyperglycaemia, hyperuricaemia was associated with a hazard ratio (HR) of 1.28 [95% confidence interval (CI) 1.23-1.33, p < 0.001] for an accelerated eGFR decline ≥ 3 mL/min/1.73 m(2) per year and an HR of 1.52 (95% CI 1.46-1.59) for CKD progression at the end of follow-up.

CONCLUSION

Hyperuricaemia was associated with an accelerated decline in eGFR and higher risk of CKD progression. Therefore, renal function should be monitored closely in patients with hyperuricaemia.

The relationship between serum uric acid and chronic kidney disease among Appalachian adults

BACKGROUND

Higher serum uric acid (SUA) levels have been shown to be associated with cardiovascular disease. SUA levels are also associated with hypertension, a strong risk factor for chronic kidney disease (CKD). However, it is unclear whether SUA is independently associated with CKD. We examined the hypothesis that higher SUA levels are positively associated with CKD.

METHODS

We analysed data from the C8 Health Study, a population-based study of Appalachian adults aged ≥18 years and free of cardiovascular disease (n = 49,295, 53% women). SUA was examined as gender-specific quartiles. The outcome of interest was CKD (n = 2,980), defined as an estimated glomerular filtration rate of <60 mL/min/1.73 m(2) from serum creatinine.

RESULTS

Overall, we observed a clear positive association between increasing quartiles of SUA and CKD, independent of confounders. Compared with the lowest quartile of SUA (referent), the multivariable odds ratios (95% confidence interval) for quartiles 2-4, respectively, of CKD were 1.53 (1.31, 1.78), 2.16 (1.86 2.50) and 4.67 (4.07, 5.36); P-trend < 0.0001. This observed positive association persisted in separate analysis among men (P-trend < 0.0001) and women (P-trend < 0.0001).

CONCLUSIONS

In conclusion, higher SUA levels are positively associated with CKD, suggesting that at least part of the reported association between SUA and cardiovascular disease may be mediated by CKD.

Association of uric acid with change in kidney function in healthy normotensive individuals

BACKGROUND

Despite recent evidence, the role of uric acid as a causal factor in the pathogenesis and progression of kidney disease remains controversial, partly because of the inclusion in epidemiologic studies of patients with hypertension, diabetes, and/or proteinuria.

STUDY DESIGN

Prospective observational cohort.

SETTING & PARTICIPANTS

900 healthy normotensive adult blood donors (153 women, 747 men) evaluated at baseline and after 5 years.

PREDICTOR

Serum uric acid level.

OUTCOMES

Decrease in estimated glomerular filtration rate (eGFR) >10 mL/min/1.73 m(2), computed using the Modification of Diet in Renal Disease (MDRD) Study equation, with secondary analyses examining similar decreases using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and Cockcroft-Gault equations.

RESULTS

During a median follow-up of 59 months, eGFR decreased from 97 +/- 16 to 88 +/- 14 mL/min/1.73 m(2). Higher serum uric acid levels were associated with a greater likelihood of eGFR decrease in both women and men (HR, 1.13 [95% CI, 1.04-1.39] per each 1-mg/dL increase in uric acid level); in multivariable analyses adjusting for age, sex, body mass index, blood glucose level, total cholesterol level, mean blood pressure, urine albumin-creatinine ratio, and serum triglyceride level, the association remained highly significant (HR, 1.28 [95% CI, 1.12-1.48]). Results were similar using different estimating equations and when the association was examined in sex-specific subgroups.

LIMITATIONS

Analyses were based on a single baseline uric acid measurement. Women are underrepresented.

CONCLUSIONS

In healthy normotensive individuals, serum uric acid level is an independent risk factor for decreased kidney function.

Hyperuricemia associated with rapid renal function decline in elderly Taiwanese subjects

BACKGROUND/PURPOSE

Hyperuricemia is encountered frequently in patients with chronic kidney disease (CKD). We tested the hypothesis that uric acid influences glomerular filtration rate (GFR) and is associated with renal function decline in elderly Taiwanese subjects.

METHODS

We enrolled 800 elderly Taiwanese subjects for a health checkup. Estimated GFR (eGFR) was measured using the Modification of Diet in Renal Disease Study equation. eGFR < 60 mL/min/1.73 m2 was used to analyze the prevalence and incidence of CKD. Significant renal function decline was defined as a decrease in eGFR of > or = 3 mL/min/1.73 m2 per year.

RESULTS

The prevalence of CKD was 18.0% in the elderly subjects. Mean serum uric acid level was 6.6 mg/dL in male and 5.6 mg/dL in female subjects, and eGFR was 71.7 mL/min/1.73 m2. Uric acid levels were associated independently and negatively with eGFR after adjusting for conventional factors of renal function decline. One hundred and sixty-two individuals (31.2%) had a significant decline in renal function. As uric acid level increased by 1 mg/dL, the odds of a significant eGFR decline increased by 1.208.

CONCLUSION

Serum uric acid level was associated with eGFR and decline in renal function in elderly Taiwanese subjects. Whether hypouricemic therapy could retard the progression of CKD deserves further in-depth study.

The Prevalence of Nephrolithiasis in Patients with Primary Gout: A Cross-sectional Study Using Helical Computed Tomography

Objective.

To investigate the prevalence of nephrolithiasis in gouty patients by computed tomography (CT) imaging and to compare it with the “prevalence” of urolithiasis calculated from histories of urinary tract calculus.

Methods.

The kidneys of 383 male patients with primary gout were examined using an unenhanced 2-row helical CT detector, imaging at 2 mm collimation and a helical pitch of 3. The urolithiasis history of the 383 patients was investigated by inquiry. Patients’ ages, body mass index, and laboratory data from a 1-hour clearance test were determined.

Results.

CT scans confirmed nephrolithiasis in 103 (26.9%, 95% confidence interval 22.5%–31.6%) of the 383 gouty patients, and history of urinary calculus was positive in 65 (17.0%, 95% confidence interval 13.4%–21.1%) of the 383. However, 64 (62%) of the 103 stone-formers identified by CT had no history of urolithiasis. There was a significant difference between the ages of the 103 stone-formers identified by CT and the 65 stone-formers identified from the history.

Conclusion.

The prevalence of nephrolithiasis obtained using CT was 26.9% in the 383 patients with primary gout. Our results imply that we cannot determine an accurate prevalence of urolithiasis from a patient’s history. Most of the “prevalence” reported in the past may not correspond to a statistically justifiable one, but instead to the “cumulative incidence” during the contraction period of gout. Thus, the prevalence of nephrolithiasis confirmed by a cross-sectional method and the “prevalence” of urolithiasis calculated from patients’ calculus histories should be clearly distinguished.

Uric acid and long-term outcomes in CKD

BACKGROUND

Hyperuricemia is prevalent in patients with chronic kidney disease (CKD); however, data are limited about the relationship of uric acid levels with long-term outcomes in this patient population.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

The Modification of Diet in Renal Disease (MDRD) Study was a randomized controlled trial (N = 840) conducted from 1989 to 1993 to examine the effects of strict blood pressure control and dietary protein restriction on progression of stages 3 to 4 CKD. This analysis included 838 patients.

PREDICTOR

Uric acid level.

OUTCOMES & MEASUREMENTS

The study evaluated the association of baseline uric acid levels with all-cause mortality, cardiovascular disease (CVD) mortality, and kidney failure.

RESULTS

Mean age was 52 +/- 12 (SD) years, glomerular filtration rate was 33 +/- 12 mL/min/1.73 m(2), and uric acid level was 7.63 +/- 1.66 mg/dL. During a median follow-up of 10 years, 208 (25%) participants died of any cause, 127 (15%) died of CVD, and 553 (66%) reached kidney failure. In multivariate models, the highest tertile of uric acid was associated with increased risk of all-cause mortality (hazard ratio [HR], 1.57; 95% confidence interval [CI], 1.07 to 2.32), a trend toward CVD mortality (HR, 1.47; 95% CI, 0.90 to 2.39), and no association with kidney failure (HR, 1.20; 95% CI, 0.95 to 1.51) compared with the lowest tertile. In continuous analyses, a 1-mg/dL greater uric acid level was associated with 17% increased risk of all-cause mortality (HR, 1.17; 95% CI, 1.05 to 1.30) and 16% increased risk of CVD mortality (HR, 1.16; 95% CI, 1.01 to 1.33), but was not associated with kidney failure (HR, 1.02; 95% CI, 0.97 to 1.07).

LIMITATIONS

Primary analyses were based on a single measurement of uric acid. Results are generalizable primarily to relatively young white patients with predominantly nondiabetic CKD.

CONCLUSIONS

In patients with stages 3 to 4 CKD, hyperuricemia appears to be an independent risk factor for all-cause and CVD mortality, but not kidney failure.

Uric acid as a risk factor for progression of non-diabetic chronic kidney disease? The Mild to Moderate Kidney Disease (MMKD) Study

The kidney is one of the organs most prominently affected by aging. This can be seen by a loss of renal mass which is caused by a decrease in the number of nephrons resulting in hyperfiltration, hypertrophy and elevations in glomerular pressure. The factors influencing aging of the kidney are not fully elucidated. Epidemiological, experimental and interventional studies resulted in inconsistent results and have not firmly established whether uric acid levels affect progression of Chronic Kidney Disease (CKD). Therefore, we analyzed whether uric acid levels predict the progression of CKD in the Mild to Moderate Kidney Disease Study comprising at baseline 227 Caucasian patients aged 18-65 years with primary non-diabetic CKD of various degrees of renal impairment. Of them, 177 completed a prospective follow-up of 7 years. Primary endpoint was progression of CKD defined as doubling of baseline serum creatinine and/or terminal renal failure. Patients who reached a progression endpoint (n =6 5) were significantly older, had higher baseline serum creatinine and protein excretion rates as well as lower Glomerular Filtration Rate (GFR). Uric acid levels were only higher in patients with progression of disease when patients with uric acid-lowering drugs were excluded from the analysis. Cox regression analysis revealed that increasing uric acid levels predict disease progression only when the analysis was not adjusted for baseline kidney function parameters. As soon as we adjusted the analysis for GFR and proteinuria this association completely vanished. In summary, our prospective 7 year follow-up study in patients with non-diabetic primary CKD did not support uric acid as an independent predictor for CKD progression.

Relationship of uric acid with progression of kidney disease

BACKGROUND

Uric acid levels are increased in patients with kidney dysfunction. We tested the hypothesis that uric acid may be associated with kidney disease progression.

STUDY DESIGN

Cohort study.

SETTING & PARTICIPANTS

5,808 participants of the Cardiovascular Health Study.

PREDICTOR

Uric acid levels.

OUTCOMES & MEASUREMENTS

Kidney disease progression was defined as a decrease in estimated glomerular filtration rate (GFR) of 3 mL/min/1.73 m(2) per year or greater (>or=0.05 mL/s) and as incident chronic kidney disease (CKD). Measures of kidney function were estimated GFR using the Modification of Diet in Renal Disease Study equation.

RESULTS

Higher quintiles of uric acid levels were associated with greater prevalences of estimated GFR less than 60 mL/min/1.73 m(2) (<1.00 mL/s) of 7%, 14%, 12%, 25%, and 42% for quintiles 1 (<or=4.41 mg/dL [<or=262 micromol/L]), 2 (4.41 to 5.20 mg/dL [262 to 309 micromol/L]), 3 (5.21 to 5.90 mg/dL [310 to 351 micromol/L]), 4 (5.91 to 6.90 mg/dL [352 to 410 micromol/L]), and 5 (>6.90 mg/dL [>410 micromol/L]), respectively. In comparison, there was only a modest, but significant, association between quintiles of uric acid levels and progression of kidney function decrease, with adjusted odds ratios of 1.0, 0.88 (95% confidence interval [CI], 0.64 to 1.21), 1.23 (95% CI, 0.87 to 1.75), 1.47 (95% CI, 1.04 to 2.07), and 1.49 (95% CI, 1.00 to 2.22) for quintiles 1 through 5, respectively. No significant association was found between uric acid level and incident CKD (adjusted odds ratio, 1.00; 95% CI, 0.89 to 1.14).

LIMITATIONS

Measurements of albuminuria were not available.

CONCLUSIONS

Uric acid levels are associated strongly with prevalent CKD. In comparison, greater uric acid levels had a significant, but much weaker, association with progression of kidney disease.

Uric Acid and renal disease

The interrelationship between uric acid and renal disease is reviewed in a historical context. Four phases can be distinguished--the descriptions of uric acid stones and gravel in the eighteenth century, of chronically scarred kidneys containing urate crystals in the nineteenth, the appearance of the syndrome of acute urate nephropathy following tumour lysis in the mid twentieth century, and finally the realization that soluble urate affects both systemic and glomerular blood vessels, and may play a role in both hypertension and chronic renal damage.

Gout: can we create an evidence-based systematic approach to diagnosis and management?

The management of gout can be subdivided into four phases. Asymptomatic hyperuricaemia represents the basic underlying metabolic abnormality that can lead to gout. Studies are evaluating whether interventions may be indicated in some cases. Diagnostic criteria for gout and acute flares are still not well defined unless urate crystals are found. Acute attacks of gout are treated with anti-inflammatory measures and the agent of choice is often determined by attack stage, severity and comorbidities that may contra-indicate one or more agents. After attacks subside, there are asymptomatic periods during which decisions must be made about when and how to start urate-lowering measures. If hyperuricaemia persists, there is generally persistence of urate crystals in the joint. Anti-inflammatory prophylaxis is needed when urate-lowering therapy is started. Lifestyle measures should be addressed. If chronic tophaceous gout is diagnosed, urate lowering should be started without delay. New agents are under development that may help with difficult cases.

Hyperuricemia and Associated Diseases

After introduction of urate-lowering therapy, asympotomatic hyperuricemia was treated with allopurinol or uricosuric agents in the belief that hyperuricemia and/or gout caused chronic kidney disease. Epidemiologic studies in the 1970s, however, failed to confirm the view that hyperuricemia and gout were independent risk factors for chronic kidney disease. As a result, urate-lowering pharmacotherapy is generally not recommended at the present time in the management of asymptomatic hyperuricemia even though recent epidemiological, experimental, and clinical studies have prompted reexamination of a causal role for hyperuricemia (with or without gout) in chronic kidney disease as well as other important disorders including cardiovascular disease, hypertension, and metabolic syndrome. The issue of such a role remains unresolved and this article reviews the current status of the relationship between hyperuricemia and associated disorders.

Essential hypertension, progressive renal disease, and uric acid: a pathogenetic link?

Hypertension and hypertension-associated ESRD are epidemic in society. The mechanisms responsible for renal progression in mild to moderate hypertension and those groups most at risk need to be identified. Historic, epidemiologic, clinical, and experimental studies on the pathogenesis of hypertension and hypertension-associated renal disease are reviewed and an overview/hypothesis for the mechanisms involved in renal progression is presented. There is increasing evidence that hypertension may exist in one of two forms/stages. The first stage, most commonly observed in early or borderline hypertension, is characterized by salt-resistance, normal or only slightly decreased GFR, relatively normal or mild renal arteriolosclerosis, and normal renal autoregulation. This group is at minimal risk for renal progression. The second stage, characterized by salt-sensitivity, renal arteriolar disease, and blunted renal autoregulation, defines a group at highest risk for the development of microalbuminuria, albuminuria, and progressive renal disease. This second stage is more likely to be observed in blacks, in subjects with gout or hyperuricemia, with low level lead intoxication, or with severe obesity/metabolic syndrome. The two major mechanistic pathways for causing impaired autoregulation at mild to moderate elevations in BP appear to be hyperuricemia and/or low nephron number. Understanding the pathogenetic pathways mediating renal progression in hypertensive subjects should help identify those subjects at highest risk and may provide insights into new therapeutic maneuvers to slow or prevent progression.

Uric acid and chronic renal disease: Possible implication of hyperuricemia on progression of renal disease

Although hyperuricemia has long been associated with renal disease, uric acid has not been considered as a true mediator of progression of renal disease. The observation that hyperuricemia commonly is associated with other risk factors of cardiovascular and renal disease, especially hypertension, has made it difficult to dissect the effect of uric acid itself. However, recent epidemiologic evidence suggests a significant and independent association between the level of serum uric acid and renal disease progression with beneficial effect of decreasing uric acid levels. Furthermore, our experimental data using hyperuricemic animals and cultured cells have provided robust evidence regarding the role of uric acid on progression of renal disease. Hyperuricemia increased systemic blood pressure, proteinuria, renal dysfunction, vascular disease, and progressive renal scarring in rats. Recent data also suggest hyperuricemia may be one of the key and previously unknown mechanisms for the activation of the renin-angiotensin and cyclooxygenase-2 (COX-2) systems in progressive renal disease. Although we must be cautious in the interpretation of animal models to human disease, these studies provide a mechanism to explain epidemiologic data that show uric acid is an independent risk factor for renal progression. Although there is no concrete evidence yet that uric acid bears a causal or reversible relationship to progressive renal disease in humans, it is time to reevaluate the implication of hyperuricemia as an important player for progression of renal disease and to try to find safe and reasonable therapeutic modalities in individual patients based on their clinical data, medication history, and the presence of cardiovascular complications.

Community-based study in Taiwan aborigines concerning renal dysfunction in gout patients

OBJECTIVE

To reveal the factors associated with renal dysfunction among gout patients in Taiwan aborigines.

METHODS

Social demographic data, alcohol consumption data, anthropometric measurements, blood samples, and 24-h urine samples were collected from 128 aboriginals (101 men, 27 women) suffering from gout.

RESULTS

The men displayed higher mean creatinine clearance (Ccr) values than women. Twenty-two post-menopausal women had significantly lower Ccr values compared to the five pre-menopausal women [probability (p)<0.001]. The males displayed higher 24-h urinary creatinine value than females (8.60+/-5.39 versus 5.58+/-2.14 mmol/L; p<0.05), and showed a significantly higher positive relationship between 24-h urinary creatinine and uric acid excretion [correlation coefficient (r)=0.7304; p<0.001], whereas the females did not (r=0.1144; p=0.5691). Overall, those who were older members of the Tsou tribe, or had excreted less uric acid from urine in 24 h tended to suffer renal dysfunction.

CONCLUSIONS

Gout patients displayed diversity in renal function. An exogenous source of creatinine in men was more likely than in women.

Quality of care indicators for gout management

OBJECTIVE

Despite the significant health impact of gout, there is no consensus on management standards. To guide physician practice, we sought to develop quality of care indicators for gout management.

METHODS

A systematic literature review of gout therapy was performed using the Medline database. Two abstractors independently reviewed each of the articles for relevance and satisfaction of minimal inclusion criteria. Based on the review of the literature, 11 preliminary quality indicators were developed and then reviewed and refined by an initial feasibility panel of community and academic rheumatologists. A twelfth indicator was added at the request of the first panel. Using a modification of the RAND/University of California at Los Angeles appropriateness method (bridging teleconference and white-board Internet technology were added), a second expert panel rated each of the proposed indicators for validity using a 9-point scale, in which ratings of 1-3, 4-6, and 7-9 were considered "invalid," "indeterminate," and "highly valid," respectively. Indicators were considered valid if the median panel rating was > or =7 and there was no evidence of panel disagreement (defined to occur when 2 of 6 panelists provided a validity rating of 1-3 and 2 panelists provided a validity rating of 7-9).

RESULTS

Ten of the 12 draft indicators were rated to be valid by our second expert panel. Validated indicators pertained to 1) the use of urate-lowering medications in chronic gout, 2) the use of antiinflammatory drugs, and 3) counseling on lifestyle modifications.

CONCLUSION

Using a combination of evidence and expert opinion, 10 indicators for quality of gout care were developed. These indicators represent an important initial step in quality improvement initiatives for gout care.