Salivary Uric Acid as a Non-Invasive Biomarker in Hypertensive Patients: A Comparative Cross-Sectional Study

Background. Hypertension is a leading global cause of cardiovascular morbidity and mortality. Uric acid (UA) is implicated in oxidative stress, endothelial dysfunction, and hypertensive pathophysiology. Salivary UA offers a non-invasive, cost-effective alternative to serum analysis. Aim: To compare salivary UA levels in hypertensive adults against normotensive controls and evaluate its diagnostic utility. Material and Methods. This prospective case-control study enrolled 60 adult hypertensive patients and 60 age- and sex-matched normotensive controls. Non-stimulated whole saliva (NWS) and stimulated whole saliva (SWS) were collected following a standardised protocol. Salivary UA concentrations were measured spectrophotometrically using a commercial QuantiChrom™ Uric Acid Assay Kit. Serum UA, total antioxidant capacity (TAC), and salivary flow rates were also assessed. Pearson correlation coefficients and receiver operating characteristic (ROC) analysis were applied for statistical evaluation. Results. SWS UA was significantly higher in the hypertensive group (18.62 ± 3.27 µg/mg protein) versus controls (6.14 ± 1.92 µg/mg protein; p < 0.001). NWS UA was similarly elevated. Salivary UA in SWS correlated positively with systolic blood pressure ( r = 0.79, p < 0.001), diastolic blood pressure ( r = 0.81, p < 0.001), and serum UA ( r = 0.84, p < 0.001). ROC analysis showed SWS UA had an AUC of 0.97 with sensitivity of 92% and specificity of 93% in differentiating hypertensive from normotensive individuals. Stimulated salivary flow was significantly lower in the hypertensive group. Conclusion. Salivary UA, particularly measured in stimulated saliva, is markedly elevated in hypertensive patients and demonstrates strong diagnostic performance. It represents a promising non-invasive biomarker for hypertension screening and monitoring, warranting validation in larger multicentre studies.