RESUMEN
BACKGROUND: Serum urea levels are essential for the diagnosis of chronic kidney disease (CKD), as they are a measure of renal function. Salivary urea has been used as an alternative to serum urea in patients with CKD. AIM: To estimate serum urea levels and their correlation with salivary urea levels in order to validate the use of saliva as an alternative diagnostic tool for renal dysfunction. PATIENTS AND METHODS: Thirty healthy individuals and 150 patients with CKD (30 from each CKD stage) were recruited for the study. Serum and salivary samples were collected to estimate the urea levels, and statistical analyses were performed. RESULTS: Statistically significant (P < 0.05) differences in the mean serum and salivary urea levels were observed between the healthy and each stage of the CKD group; significance at P < 0.05 was observed within the stages of CKD as well. Correlation analysis also showed significant differences between the serum and salivary urea levels at each stage of the disease. Receiver operating characteristic analysis revealed a higher area under the curve of 0.917 at a 95% confidence interval with a salivary urea cut-off of 28.25 mg/dl (sensitivity and specificity: 88% and 84%, respectively). CONCLUSION: The variability in salivary urea levels in the early and late stages suggests the use of salivary urea in the late stages of CKD. It is suggested that salivary urea levels may be used as an alternative to serum to assess and monitor the progression of renal impairment along with other standard renal function markers.
