Evaluation of Hemodialysis Efficacy for Serum and Salivary Clearance of Urea, Creatinine, and Uric Acid in Chronic Kidney Disease Patients

Abstract

ackground: Chronic kidney disease (CKD) is a progressive and irreversible loss of kidney function that may progress to end-stage renal disease requiring hemodialysis. While hemodialysis is an established life-saving therapy, simple methods to assess its adequacy are needed. This study evaluated changes in urea, creatinine, and uric acid levels in serum before and after hemodialysis and compared them with salivary levels to assess the adequacy of hemodialysis. Materials and Methods: A case-control study was conducted on 32 patients undergoing hemodialysis and 30 healthy controls. Blood and saliva samples were collected immediately before and after dialysis from patients and controls. Serum and salivary levels of markers were analyzed by biochemical methods. Serum and salivary levels of markers were compared between the patient group and the control group by t-test and the diagnostic accuracy of salivary markers compared to serum markers was evaluated by the receiver-operating characteristic (ROC) curve and area under the curve (AUC). Results: There were significant differences between the serum and salivary levels of urea, creatinine, and uric acid in patients before and after hemodialysis, and also with the control group (P<0.05). There was a positive correlation between the serum and salivary levels of urea, creatinine and uric acid before hemodialysis, and creatinine after hemodialysis. The AUC for salivary urea and creatinine was 0.87 and 0.88, respectively, and the cut-off point for urea and creatinine was 55 mg/dL and 0.5 mg/dL, respectively. The ROC analysis for uric acid was not significant. Conclusion: This study showed that before hemodialysis, the changes in salivary urea, creatinine, and uric acid in CKD patients (in the fasting state) were similar to serum. Additionally, after hemodialysis, changes in salivary creatinine levels were similar to serum. Therefore, saliva analysis is suggested as a non-invasive alternative to serum analysis for assessment of the efficacy of hemodialysis.