Management and Cure of Gouty Arthritis

Gout is the most common inflammatory arthritis in the United States. Gouty arthritis is associated with significant morbidity and mortality and is caused by hyperuricemia. Gout is effectively managed and potentially cured by decreasing the overall urate burden with serum urate-lowering therapy. When serum urate is maintained at less than 6.0 mg/dL urate deposition is resolved and gout can be cured. Unfortunately, owing to a lack of physician monitoring and dose escalation the majority of patients do not achieve these urate levels.

A Retrospective Cohort Study of the Effect of Gout on Mortality Among Patients with a History of Kidney Transplantation

Background

Kidney transplantation is associated with increased prevalence of gout. However, evidence of the effect of gout on long-term kidney transplantation outcomes is mixed. This study examined mortality risk among patients with a history of kidney transplantation with vs. without gout.

Material/Methods

A retrospective study was conducted using Medicare Fee-for-Service administrative claims of patients with a history of kidney transplantation. Cox proportional hazards models determined the effect of gout on all-cause mortality, controlling for confounders, including comorbid mortality risk, via the Charlson Comorbidity Index. Because the relationships between gout and components of the Charlson Comorbidity Index are also debated, 3 different model assumptions were used: 1) gout shares a common cause with these comorbidities, 2) gout is upstream of these comorbidities, 3) the effect of gout on mortality is modified by these comorbidities.

Results

Gout increased the risk of all-cause mortality in the unadjusted model (hazard ratio: 1.44, 95% CI 1.27–1.63) and after adjustment for demographics and transplant vintage (hazard ratio: 1.16, 95% CI 1.02–1.32). Gout was not a significant risk after adjustment for baseline Charlson Comorbidity Index (hazard ratio: 1.03, 95% CI 0.90–1.17). Gout was associated with greater mortality among patients without baseline comorbidities (Charlson Comorbidity Index=0; hazard ratio: 3.48, 95% CI 1.27–9.57) in the stratified model.

Conclusions

Among patients with a history of kidney transplantation, gout did not have an independent effect on all-cause mortality. However, gout was a predictor of mortality among patients with no comorbidities, suggesting that gout is an early warning sign of poor health in kidney transplantation patients.

Immunosuppressant Use and Gout in the Prevalent Solid Organ Transplantation Population

INTRODUCTION

Gout is a common comorbidity among solid organ transplantation patients and is usually attributed to the use of cyclosporine. This study aims to evaluate the prevalence of gout among solid organ transplantation patients to determine the prevalence in the tacrolimus era.

RESEARCH QUESTIONS

To what degree is cyclosporine still used among prevalent solid organ transplantation patients? How prevalent is gout in the solid organ transplantation population not being treated by cyclosporine?

METHODS

Immunosuppressant regimens and gout prevalence among prevalent solid organ transplantation patients were assessed using retrospective claims data for a representative sample of commercially insured patients. For comparison to the prevalent solid organ transplantation population, immunosuppressant use at time of transplantation was compiled from published reports.

RESULTS

Between 2012 and 2016, the use of cyclosporine declined while use of tacrolimus increased, with greater cyclosporine use among prevalent versus incident solid organ transplantation patients. The prevalence of gout was 18.3%, 9.3%, and 9.1% for solid organ transplantation patients on cyclosporine, tacrolimus, and neither, respectively. Among all solid organ transplantation patients with gout, 66.6% and 21.5% were on tacrolimus versus cyclosporine. The prevalence of gout among noncyclosporine solid organ transplantation patients was significantly higher than in the general population without solid organ transplantation.

DISCUSSION

Despite declining cyclosporine use, gout prevalence remains high, with the majority of patients with gout receiving tacrolimus rather than cyclosporine. In summary, gout remains a frequent comorbidity of solid organ transplantation.

Prevalence of Gout in the Surviving United States Solid Organ Transplantation Population

PURPOSE

Although incidence and survival are frequent topics within the solid organ transplantation (SOT) literature, the size of the surviving SOT population is not well known. Existing studies of gout in patients with SOT have focused on the incident SOT population. This analysis was performed to characterize the prevalent SOT population and the prevalence of gout within it.

METHODS

This study includes the 2017 United States (US) population size of recipients of kidney, heart, liver, and lung transplants that was estimated by combining primary transplant recipient cohort sizes (1988-2017) with previously published survival rates for each annual cohort's time since transplantation (0-29 years). Gout among prevalent patients with SOT was assessed using Medicare and commercial claims.

RESULTS

A total of 637,231 US patients received a primary kidney (393,953), liver (142,186), heart (66,637), or lung (34,455) transplant between 1988 and 2017. An estimated 356,000 (55.8%) recipients were alive in 2017 (233,000 kidney; 78,700 liver; 29,300 heart; 14,700 lung). Gout was identified in 11% of prevalent patients with SOT in 2016. Higher rates of gout were seen in recipients of kidney (13.1%) and heart (12.7%) compared to recipients of liver (6.7%) and lung (5.6%) (P < .0001 in both datasets). Active diagnosed gout prevalence in the US population without a SOT history was 1.1% in 2016.

CONCLUSIONS

Hundreds of thousands of US patients are living with a transplanted organ today and these numbers are likely to increase. In patients with SOT, gout is a frequent comorbidity of which physicians should be aware. This study suggests a markedly higher rate of gout among transplant recipients compared to the general US population.

Gout Severity in Recipients of Kidney Transplant

PURPOSE

This retrospective analysis of medical chart data was performed to compare severity and treatment of gout in patients with or without a history of kidney transplantation (KT).

METHODS

Via an online survey, a panel of board-certified US nephrologists (N = 104) provided the following deidentified chart data for their 3 most recent patients with gout: age, sex, serum uric acid, numbers of swollen or tender joints, visible tophi, gout flare events (prior 12 months), gout drug treatment history, and KT history. The presence of "severe, uncontrolled gout" was defined as: serum uric acid ≥ 7.0 mg/dL, ≥1 tophi and ≥2 flares in the last 12 months, and history of xanthine oxidase inhibitor treatment.

RESULTS

Twenty-five out of 312 (8.0%) gout patients had a history of KT. Univariate analysis found that patients with gout and history of kidney transplants had: greater prevalence of severe uncontrolled gout (27% vs 8%, P = .007) and tophi (36% vs 17%, P = .030), and higher rates of failure or physician perceived contraindication to allopurinol (44% vs 23%, P = .028).

CONCLUSION

This study provides preliminary evidence that gout in patients with history of KT is more severe and poses greater challenges to pharmacologic management. Although gout has been linked to worse outcomes among kidney recipients in the literature, there are presently no publications on gout severity among patients with KT in comparison to other patients with gout. Further investigation of disease severity and appropriate, effective treatment options in recipients of kidney transplant with a diagnosis of gout, especially prior to the transplant, is warranted.

Tophus resolution in patients with chronic refractory gout who have persistent urate-lowering responses to pegloticase

BACKGROUND

Pegloticase is a recombinant mammalian uricase conjugated to polyethylene glycol approved in the United States for treatment of chronic refractory gout. It can profoundly decrease serum urate to < 1 mg/dl. In patients receiving pegloticase who did not generate high-titer antidrug antibodies (responders), the serum urate remained low for the duration of therapy, 6 months in the phase III clinical trials plus the open-label extension. The objective of this study was to assess the velocity of tophus resolution in subjects treated with pegloticase.

METHODS

Data from two randomized controlled trials of pegloticase in chronic refractory gout were analyzed. Tophi were assessed by computer-assisted measurements of standardized digital photographs. Subjects were designated as responders and nonresponders based on maintenance of serum urate < 6 mg/dl at months 3 and 6 of treatment. The projected time of complete resolution of all tophi was determined by linear regression analysis.

RESULTS

The mean total tophus area at baseline was 585.8 mm² for responders, 661.5 mm² for nonresponders, and 674.4 mm² for placebo-treated patients. Complete resolution at 6 months of at least one tophus was achieved by 69.6% of 23 responders, 27.9% of 43 nonresponders, and 14.3% of 21 patients who received placebo. Complete resolution of all photographed tophi was achieved by 34.8% of biochemical responders, 11.6% of nonresponders, and 0% of placebo-treated patients. The mean velocity of resolution of all tophi was 60.1 mm²/month in responders with a mean projected time of complete resolution of 9.9 months (4.6-32.6 months). There was a significant inverse correlation between serum urate AUC and tophus resolution velocity (r = - 0.40, P = 0.0002), although considerable heterogeneity in the velocity of resolution was noted. The only patient characteristic that correlated with the velocity of tophus resolution was the baseline tophus area.

CONCLUSIONS

Pegloticase treatment caused a rapid resolution of tophi in responders that correlated with the serum urate lowering associated with this therapy.