Effect of serum uric acid level on prognosis in maintenance hemodialysis patients

Objective To analyze the relationship between serum uric acid (SUA) level and clinical indicators in maintenance hemodialysis (MHD) patients, and explore its influence on all-cause mortality and cardiovascular mortality. Methods This study was a retrospective cohort study. Patients who received MHD from the blood purification center of the Third Affiliated Hospital of Sun Yat-sen University from January 1, 2011 to December 30, 2015 were enrolled in the queue. They were divided into 3 groups according to the first and third quantile of the SUA level quartiles, and the baseline data of clinical and laboratory examinations were compared. The correlation between SUA level and clinical indicators was analyzed by Pearson correlation coefficient. Kaplan-Meier method and Cox proportional hazard regression model were used to examine the association between SUA and all-cause mortality and cardiovascular mortality in MHD patients. Results A total of 201 patients were enrolled in the study. The age of the patients was (56.9±16.7) years and the baseline SUA level was (531.1±137.9) μmol/L. Patients were divided into 3 groups with the first quantile (442 μmol/L) and the third quantile (620 μmol/L) of the SUA quartiles as the boundary points: group 1 (SUA＜442 μmol/L, n=52), group 2 (SUA 442-620 μmol/L, n=101) and group 3 (SUA＞620 μmol/L, n=48). The results showed that the patients in group 1 were older and had more proportion of patients with diabetes mellitus and cardiovascular diseases than those in group 3 (all P＜0.05). Compared to group 3, the serum albumin, serum phosphorus and serum creatinine were lower in group 1, while the hypersensitive C-reactive protein was higher (all P＜0.05). Pearson correlation analysis showed that SUA level was positively correlated with albumin (r=0.135, P=0.047), blood phosphorus (r=0.269, P＜0.001) and serum creatinine (r=0.333, P＜0.001), and negatively correlated with hypersensitive C-reactive protein (r=-0.216, P=0.002). After a median follow-up of 49.8 months, 66(32.8%) all-cause deaths and 32(15.9%) cardiovascular deaths were recorded. Kaplan-Meier method showed that with the decrease of SUA, all-cause mortality (Log-rank χ2=18.27, P＜0.001) and cardiovascular mortality (Log-rank χ2=15.04, P=0.001) increased. After adjusting for age, gender, comorbidity and other factors using the Cox proportional hazards model, the all-cause mortality and cardiovascular mortality decreased by 20.1% (HR=0.799, 95% CI 0.651-0.980, P=0.031) and 29.6% (HR=0.704, 95% CI 0.524-0.946, P=0.020) for each 100 μmol/L increase in baseline SUA. Compared to group 1, all-cause mortality (HR=0.332, 95%CI 0.142-0.774, P=0.011) and cardiovascular mortality (HR=0.140, 95%CI 0.030-0.657, P=0.013) were lower in the group 3. Conclusion Low SUA level increases the risk of all-cause mortality and cardiovascular mortality in MHD patients.