Background/Purpose: Cardiovascular events, chronic kidney disease and increased mortality are common in gout patients but what links them remains unclear. Tophaceous gout in particular is associated with higher mortality which raised the potential causal role of the monosodium urate (MSU) crystal burden. The volume of MSU crystal deposition in soft tissues measured with dual-energy computed tomography (DECT) is cross-sectionally associated to cardiovascular diseases. The objective of this study was to determine if the initial volume of MSU crystal deposition measured with DECT is predictive of the mortality risk and development of cardiovascular and kidney diseases.

Methods: From April 2016 to May 2019, we prospectively enrolled in the CRYSTALILLE inception cohort of gout patients to undergo baseline DECT scans of both knees and ankles/feet.

Data including disease history and treatment, existing comorbidities, serum urate levels, estimated glomerular filtration rate (eGFR), and volume of MSU crystal deposition measured with DECT at the ankles/feet and knees were assessed at baseline. Data on the onset of major cardiovascular events (MACEs) and mortality, serum urate and eGFR were collected for months 12, 24 and 36. Baseline factors associated with evolution of the eGFR (±5 points of change was considered significant) were studied at months 12, 24 and 36, as well as those associated with MACEs and mortality.

Results: A total of 135 patients were enrolled, they were aged 66 years (±14) years and had a disease duration of 11 years (±10). Patients had baseline serum urate levels of 7.4 mg/dL (±2.2), 62% were naïve of urate lowering therapy and 36% had tophaceous gout. At baseline, 25% of patients had diabetes mellitus, 19% had a history of myocardial infarction, 11% of stroke, and 9% of transient cerebral ischemia.

Follow-up data was available for 123 patients at month 12, 86 at month 24 and 44 at month 36. All-cause mortality was 12% (n=14) during follow-up (Figure 1). In univariate analysis, patients that were deceased during follow-up had a median initial volume of MSU crystal deposition at the knees and feet of 0.4cm³ [0.2 ; 2.9] and those who survived had a baseline volume of 0.2 cm³ [0 ; 0.9] (p=0.045). In the multivariate cox model, factors influencing the risk of all-cause mortality were the volume of MSU crystals measured with DECT (HR 1.02 (1.008-1.04) for each additional cm³), taking with renin-angiotensin inhibitors (HR 0.13 (0.016-0.99)) and taking any anti-hypertensive drugs (HR 7.37 (1.605-33.80)) (Figure 2).

The average serum urate level at months 12 was 5.6 mg/dL (±1.7), 5.9 mg/dL (±2.2) at month 24 and 5.8mg/L (±2.0) at month 36. Overall, at months 12, 24 and 36, 16%, 15% and 21% respectively of patients had improved their eGFR while 36%, 34% and 31% had degraded their eGFR compared to baseline. Neither reaching serum urate levels below 6.0mg/dL nor the initial volume of MSU crystal deposition measured with DECT were predictive of eGFR evolution. A total of 6 (5%) patients presented non-fatal MACE, which was too few to identify predictive factors.

Conclusion: The volume of MSU crystal deposition at the knees and ankles/feet is an independent predictor of short-term mortality in gout patients.

Figure 1. Kaplan-Meyer survival curve.

Figure 2. Cox Hazard ratios of factors predictive of short-term mortality in gout patients (within 36 months).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dual-energy-ct-predicts-mortality-in-gout-patients-a-3-year-follow-up-cohort-study/