Prognostic Value of Serum Uric Acid in Patients on the Waiting List before and after Renal Transplantation

Serum Uric Acid and Mortality Risk Among Hemodialysis Patients

INTRODUCTION

Although high serum uric acid (SUA) has been consistently associated with an increased risk of death in the general population and in persons with nondialysis chronic kidney disease (CKD), studies in patients undergoing dialysis are conflicting. It has been postulated that low SUA simply reflects poor nutritional status in dialysis patients. We here characterize the association between SUA and the risk of death in a large dialysis cohort and explore effect modification by underlying nutritional status as reflected by body composition.

METHODS

In this retrospective cohort study, we included 16,057 hemodialysis (HD) patients treated during 2007 to 2016 in NephroCare centers as recorded in the European Clinical Database (EuCliD). The association between SUA, all-cause, and cardiovascular (CV)-related mortality was evaluated with competing risk models and characterized with splines. Effect modification was explored by lean tissue index (LTI) and fat tissue index (FTI).

RESULTS

During a mean of 1.8 years of follow-up, 2791 patients (17.4%) died. We found a multivariable-adjusted U-shaped pattern between SUA and all-cause mortality. Patients with SUA levels of 6.5 mg/dl (387 μmol/l) were at the lowest risk of death (subdistribution hazard ratio = 0.94 [confidence interval {CI} 0.91; 0.96]). The form of association was not meaningfully affected by underlying LTI and FTI.

CONCLUSION

We found a U-shaped pattern between SUA levels and all-cause mortality among HD patients, which was independent of the patients' body composition.

Uric acid and left ventricular hypertrophy: another relationship in hemodialysis patients

Background

The impact of serum uric acid (UA) on morbidity and mortality in hemodialysis (HD) patients is quite controversial in relation to the general population. The aim of this study was to evaluate the association of serum UA with both mortality and left ventricular hypertrophy (LVH) in HD patients.

Methods

This longitudinal study enrolled 225 prevalent HD patients who were classified into three groups according to their follow-up-averaged UA (FA-UA) levels: low FA-UA (FA-UA <400 µmol/L), intermediate/reference FA-UA (FA-UA between 400 and 450 µmol/L) and high FA-UA (FA-UA >450 µmol/L). Echocardiography was performed on a nondialysis day and the presence of LVH was defined based on a left ventricular mass index (LVMI) >131 and >100 g/m² for men and women, respectively. The patients were followed during a 60-month period.

Results

The mean FA-UA level was 425 ± 59 µmol/L (range 294–620). There was a consistent association of higher FA-UA with better nutritional status (higher body mass index, normalized protein catabolic rate, creatinine, albumin and phosphorus), higher hemoglobin, but lower C-reactive protein and LVMI. During the 5-year follow-up, 81 patients died (36%) and the main causes of death were cardiovascular (CV) related (70%). When compared with the reference group, the hazard ratio for all-cause mortality was 1.75 [95% confidence interval (CI) 1.02–2.98; P = 0.041] in the low FA-UA group, but there was no significant association with the high FA-UA group. In contrast, FA-UA did not show an association with CV mortality neither with the lower nor with the high FA-UA group. The unadjusted odds ratio (OR) of LVH risk in the low FA-UA compared with the reference FA-UA group was 3.11 (95% CI 1.38–7.05; P = 0.006), and after adjustment for age, gender, diabetes and CV disease, ORs for LVH persisted significantly only in the low FA-UA group [OR 2.82 (95% CI 1.16–6.88,); P = 0.002].

Conclusions

Low serum UA is a mortality risk factor and is associated with LVH in HD patients. These results are in contrast with the association of UA in the general population and should be the subject of further research.