Subcutaneous Tophi to Predict Mortality in Gout

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Subcutaneous tophi were an independent risk factor for both cardiovascular- and non-cardiovascular-related mortality.
Subcutaneous tophi were an independent risk factor for both cardiovascular- and non-cardiovascular-related mortality.

Researchers from New Zealand found that patients with gout with a disease duration of less than 10 years have an increased risk for mortality. The findings were published in the Journal of Rheumatology.1

"Our study has shown that older age, diuretic use, and the presence of subcutaneous tophi are independent risk factors for all-cause mortality in people with gout early in their disease course (< 10 yrs of disease duration)," Nicola Dalbeth, MBChB, MD, FRACP, from the University of Auckland in New Zealand, and colleagues wrote. "The presence of subcutaneous tophi predicts mortality, both from [cardiovascular] and non-[cardiovascular] causes."

Dr Dalbeth and colleagues performed a prospective observational study of 295 participants who were diagnosed with gout less than 10 years ago and followed for a minimum of 1 year, with a mean follow-up of 5.1 ± 1.6 years. The researchers used primary and secondary health records to determine mortality and created standardized mortality ratios and risk factors for mortality.

At the conclusion of the study, 43 patients had died, with a standardized mortality ratio of 1.96 (95% CI, 1.44-2.62). Cox proportional hazard models showed that patients who were between 70  and 80 years old (hazard ratio [HR], 9.96; 95% CI, 3.30-30.03), or between 80 and 91 years old (HR, 9.39; 95% CI, 2.68-32.89), were of Māori or Pacific ethnicity (HR, 2.48; 95% CI, 1.17-5.29), used loop diuretics (HR, 3.99; 95% CI, 2.15-7.40), had a 10 µmol/L change in their serum creatinine levels (HR, 1.04 [per change]; 95% CI, 1.00-1.07), subcutaneous tophi (HR, 2.85; 95% CI, 1.49-5.44), and an increased mortality risk.

"We have previously reported that early development of tophi in this cohort is associated with reduced kidney function," Dr Dalbeth and colleagues wrote. "It is possible that development of tophi early in the course of disease reflects other comorbid conditions, such as kidney disease, that are true risk factors for mortality."

The researchers noted that subcutaneous tophi were an independent risk factor for both cardiovascular (CV)-related mortality (HR, 3.13; 95% CI, 1.38-7.10) and non-cardiovascular-related mortality (HR, 3.48; 95% CI, 1.25-9.63) in the study.

Summary & Clinical Applicability

"Our prospective observational study has shown that people with gout for less than 10 years have a 2-fold increased risk of death over an average of 5 years of observation compared with the general population," Dr Dalbeth and colleagues wrote. "The presence of tophi at baseline is an important risk factor for death from all causes and is independently associated with both CV and non-CV causes of death. The presence of tophi at baseline was associated with an almost 3-fold increased risk of death from all causes."

Limitations & Disclosures

The researchers noted several limitations of the study, including the potential for missing incidences of subclinicial tophi because of how they determined subcutaneous tophi; because 26% of the cohort consisted of Māori or Pacific Islander patients with an independent risk for CV and non-CV-related mortality unrelated to gout; because of the low number of deaths in follow-up; and because of overestimating the mortality rate as a result of a tendency for more severely ill patients to enroll in research studies.

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Reference

  1. Vincent ZL, Gamble G, House M, et al. Predictors of mortality in people with recent-onset gout: a prospective observational study. J Rheumatol. 2017;44(3):368-373. doi: 10.3899/jrheum.160596
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