Salivary creatinine and urea in patients with end-stage chronic kidney disease could not be used as diagnostic biomarkers for the effectiveness of dialysis treatment.

INTRODUCTION: End-stage chronic kidney disease (CKD) is characterized by kidney failure with the organ's functions reduced or lost completely, where the kidneys are incapable of filtering excess fluids. Renal replacement therapy may be provided by peritoneal dialysis, hemodialysis or renal transplantation. Among the key indicators for tracking patients' current status are urea and creatinine levels. AIM: The study analyzed saliva as a medium to detect and measure urea and creatinine levels in end-stage CKD patients as well as to use it as criteria for the effectiveness of the dialysis treatment by comparing salivary urea and creatinine levels with their blood levels. MATERIAL AND METHODS: The study targeted 70 end-stage CKD patients from northeastern Bulgaria undergoing hemodialysis treatment. The urea in blood serum was carried out using the UV kinetic method. Creatinine levels were measured using Jaffe reaction colorimetric method without deproteinezation, adapted on an Olympus AU 400 automated biochemical analyzer (Beckman Coulter Inc., USA). Samples from whole unstimulated saliva were collected in a 15 ml sterile test tube as per Navazesh method. The qualitative determination of salivary urea was performed using the UV kinetic method. Creatinine levels in whole unstimulated saliva were measured using Jaffe reaction colorimetric method. RESULTS: There was a statistically significant reduction in blood urea levels (P=0.000) and in blood creatinine levels (P = 0.000) following hemodialysis. The results revealed that there was no statistically significant dependence between both, the urea levels (P=0.240) and the creatinine levels (P=0.065) in whole unstimulated saliva obtained prior to and after a hemodialysis. CONCLUSIONS: Despite the parallel increase of the urea and creatinine levels in blood serum and in whole unstimulated saliva in end-stage CKD, salivary urea and creatinine levels could not be used as diagnostic biomarkers for the effectiveness of dialysis treatment.