Comparison of Rates of Lower Extremity Amputation in Patients With and Without Gout in the US Department of Veterans Affairs Health System

Importance: Cardiometabolic and other risk factors could render patients with gout more likely to undergo lower extremity amputation (LEA). Objective: To examine the rate of and factors associated with LEA in patients with gout. Design, Setting, and Participants: In this matched cohort study using national administrative data, multivariable Cox proportional hazards regression models were used to examine the associations of gout with LEA. In analyses limited to patients with gout, attributes of serum urate control and treatment with urate-lowering therapy were examined as factors associated with LEA. This study included patients who used US Department of Veterans Affairs services from January 1, 2000, to July 31, 2015. Patients with gout were identified using diagnostic codes and matched with up to 10 controls by age, sex, and year of benefit enrollment. Data analysis was performed from January 26, 2021, to September 3, 2021. Exposures: Gout classification served as the primary independent variable of interest. In analyses limited to patients with gout, factors associated with serum urate control and urate-lowering therapy were examined. Main Outcomes and Measures: Overall LEA, as well as toe, transmetatarsal, below-the-knee, and above-the-knee amputation. Results: This cohort study included 5 924 918 patients, 556 521 with gout (mean SD age, 67 12 years; 550 963 (99.0%) male; 88 853 16.0% Black non-Hispanic; 16 981 4.3% Hispanic/Latinx; 345 818 62.1% White non-Hispanic; 80 929 14.5% with race and ethnicity data missing; and 23 940 4.3% classified as other) and 5 368 397 without gout (mean SD age, 67 12 years; 5 314 344 99.0% male; 558 464 10.4% Black non-Hispanic; 204 291 3.0% Hispanic/Latinx; 3 188 504 59.4% White non-Hispanic; 1 257 739 23.4%) with race and ethnicity data missing; and 159 399 3.0% classified as other). Compared with patients without gout, patients with gout were more likely to undergo amputation, an increased rate that remained after adjustment (adjusted hazard ratio, 1.20; 95% CI, 1.16-1.24) and was highest for below-the-knee amputation (adjusted hazard ratio, 1.59; 95% CI, 1.39-1.81). In those with gout, poor serum urate control (mean >7 mg/dL during the preceding year) was associated with a 25% to 37% increase in the rate of amputation. In contrast, treatment with urate-lowering therapy was not associated with the LEA rate. Conclusions and Relevance: In this matched cohort study, patients with gout were more likely to undergo LEA. This increase was independent of other comorbidities that have been associated with amputation, including diabetes and peripheral vascular disease. Serum urate control was independently associated with the LEA rate, suggesting the possibility that lower extremity amputation may be preventable in some patients.