MTPPI's Population Health research team collaborated with Horizon Therapeutics and the Wake Forest School of Medicine to conduct a retrospective cohort study that evaluated the clinical correlates of gout and its impact on patients undergoing chronic dialysis.
image courtesy of Kidney360
Bethesda, MD - MTPPI's Population Health practice is pleased to announce that its research collaboration with Horizon Therapeutics and the Wake Forest School of Medicine has been featured in the American Society of Nephrology's Kidney360 publication.
The team used data from the United States Renal Data System (USRDS) to conduct a population-based retrospective cohort study in adult patients covered by Medicare and on dialysis in 2017. The project goal was to build on existing research into the association between gout and non-dialysis chronic renal disease by investigating the prevalence, treatment protocols, anemia management strategies, and outcomes in gout patients with ESKD undergoing dialysis. Specific to this goal, researchers assessed the prevalence of gout in US patients on maintenance dialysis, described the main characteristics associated with the presence of gout, examined medication prescription and anemia management patterns between gout and non-gout patients, and estimated gout's impact on patient outcomes such as hospitalization and mortality.
In order to identify patients with prevalent gout, the team defined a primary case of gout by requiring the existence of ≥1 claim(s) in 2017 with a ICD-10-CM code of M10.0-M10.4, M10.9, M1A.0-M1A.4, or M1A.9 at either an outpatient or a hospital visit. As a sensitivity analysis, researchers applied a more restrictive case definition of gout, which comprised individuals with at least two outpatient diagnoses of gout or at least one principal diagnosis of gout from a hospitalization. The three outcomes of interest, evaluated during study follow-up period (2018), were: (1) presence of gout among patients on maintenance dialysis during 2017 as described above; (2) all-cause mortality, defined as death within 365 days starting January 1, 2018; and (3) composite outcome including death and hospitalization for myocardial infarction (MI), stroke, or congestive heart failure (CHF), identified from the 2018 hospitalization file using the International Classification of Diseases 10th Revision (ICD-10) diagnosis codes.
The study included 231,841 adult patients who were continuously on dialysis for the entire year of 2017 and enrolled in Medicare Part A and B. Of these, 31,300 (13.5%) had at least one gout diagnosis and 200,541 (86.5%) had no gout diagnosis claims. In addition, for the patients with at least one gout diagnosis, approximately 75% had ≥1 gout diagnosis in the previous 2 years, indicating that a majority of patients had a pre-existing gout diagnosis. Consistent with the Medicare ESKD dialysis population, study patients were mostly male (56%), White (55%), and aged 65 years or older (45%). More than 85% had ≥2 years of dialysis duration, and 6% had previously received a kidney transplant. At the end of the 12-month study follow-up, 39,970 (17.2%) patients had died, 301 (0.13%) had a kidney transplant, and 7,456 (3.22%) were censored due to being lost to follow-up. For patients with gout and non-gout patients, the respective observed mortality rates were 26 and 20 per 100 patient-years. The unadjusted hazard ratios (HRs) for death and a composite of death and CVD hospitalization in the gout versus non-gout group were 1.28 (95% CI, 1.25 to 1.32) and 1.31 (95% CI, 1.28 to 1.33), respectively. After adjustment for patient characteristics and comorbid conditions, multivariable Cox proportional hazards regression analyses indicated that the presence of gout compared with non-gout was associated with a 3% increased hazard for death (HR, 1.03; 95% CI, 1.00 to 1.06) and a 6% increased risk for a composite of death of CVD hospitalization (HR, 1.06; 95% CI, 1.04 to 1.10).
This study found a 15% prevalence of gout among patients who had been on dialysis for 5 years and demonstrates that gout is a common diagnosis among dialysis patients. Patients with gout on dialysis have a higher risk for mortality and cardiovascular disease–related hospitalization. This finding is consistent with several studies also finding gout as an independent risk factor for all-cause and CVD-related mortality. This is congruent with evidence demonstrating how MSU deposition can occur in body tissues beyond peripheral joints. Recent studies using dual energy–computed tomography scanning reveal MSU deposition within coronary arteries and thoracic aortas of 86.4% of patients with gout compared with within 14.9% of non-gout patients. Whether these arterial MSU deposits result in a local inflammatory risk or the overall MSU burden causes a systemic inflammatory state that increases cardiovascular risk remains to be clarified by further investigation. Patients with ESKD on dialysis represent a vulnerable group of patients with a high risk for mortality and morbidity within the US population. Among the multiple comorbidities that make this a challenging disease state for providers to manage, our findings reflect a high prevalence of gout in these individuals and that it is an independent risk factor for mortality and cardiovascular disease–related hospitalization. The finding that patients with gout on dialysis require higher doses of ESA therapy generates the additional hypothesis that patients with gout may experience chronic subclinical inflammation that underlies this mortality and CVD risk. Notwithstanding the complexity of medical care required for these patients, these results suggest a significant opportunity exists to improve both quality of life and potentially cardiovascular risk in dialysis-dependent patients with coexisting gout.
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