European Journal of Cardiovascular Medicine

Cancer detection at an early stage substantially improves treatment outcomes and survival rates. Traditional diagnostic tools are often invasive, expensive, or unavailable in under-resourced healthcare settings. Recent research has turned attention toward saliva as a diagnostic fluid due to its non-invasive nature and ease of collection. Salivary components reflect physiological and pathological states and may contain biomarkers indicative of systemic diseases, including cancer.

Nitrite and uric acid are two such salivary biomarkers. Nitrite, a metabolite of nitric oxide, has been associated with inflammation and oxidative stress—both hallmarks of cancer. Uric acid, a known antioxidant, may also be elevated in response to malignancy-associated metabolic changes. This study investigates their levels in cancer patients compared to healthy controls and evaluates their utility as diagnostic markers.

Study Design and Participants - This observational case-control study included 100 participants: 50 Histopathologically confirmed cancer patients and 50 age- and sex-matched healthy controls. Participants were recruited from a OPD and IPD of Index Medical College Hospital & R .C, Indore, M.P in Central India. Inclusion criteria for cases were a confirmed cancer diagnosis without prior treatment. Controls had no history of cancer or systemic disease.

Sample Collection and Biomarker Quantification- Unstimulated saliva samples were collected in sterile containers, processed immediately, and stored at −20°C until analysis. Salivary nitrite levels were measured using the Griess reaction, while uric acid levels were quantified via enzymatic colorimetric assays.

Statistical Analysis- Data were analyzed using descriptive and inferential statistics. Independent t-tests compared biomarker levels between groups. ROC curve analysis was used to assess diagnostic performance, including area under the curve (AUC), sensitivity, specificity, and optimal cut-off values.

This section presents a comparative analysis of salivary nitrite and uric acid levels between cancer patients and healthy controls, along with their diagnostic performance based on ROC analysis and biomarker combination strategies.

Table 1-Biomarker Levels in Cancer vs. Controls

Table 1: Comparison of mean salivary nitrite and uric acid levels between cancer patients and controls.

Table 2- ROC Curve Analysis

Table 2: Diagnostic performance of individual biomarkers based on ROC curve analysis.

Table 3- Combined Biomarker Performance

Table 3: Sensitivity, specificity, and diagnostic accuracy for various combinations of salivary biomarkers.

Table 4- Stratified Biomarker Levels by Cancer Type

Table 4: Salivary biomarker concentrations stratified by cancer subtype.

Table 5- Correlation between Nitrite and Uric Acid

Table 5: Correlation between salivary nitrite and uric acid levels in cancer patients and healthy controls.

The results of this study strongly indicate that salivary nitrite and uric acid levels are elevated in cancer patients, corroborating their potential role as diagnostic biomarkers. Notably, salivary nitrite showed superior diagnostic performance (AUC = 0.851), demonstrating both high sensitivity (84%) and specificity (80%) at the optimal threshold. This aligns with findings from Zhang et al. (2016), who reported elevated salivary nitrite in oral cancer patients, reinforcing the biomarker’s link to inflammatory and oxidative processes inherent in carcinogenesis.

Similarly, salivary uric acid levels were significantly elevated in the cancer group, with an AUC of 0.762. These findings are consistent with those of Ghallab et al. (2014), who observed higher uric acid concentrations in cancer patients' saliva, attributing the elevation to increased xanthine oxidase activity and cell turnover.

The combined biomarker approach, which yielded a diagnostic accuracy of 83%, offers clinical value, especially in enhancing specificity (88%) when both markers are positive. This is in agreement with a meta-analysis by Nunes et al. (2018), suggesting that multi-marker panels significantly improve diagnostic yield in salivary diagnostics.

Unlike invasive biopsy or imaging techniques, salivary testing is inexpensive, painless, and easily repeatable, making it ideal for low-resource settings or mass screenings. While several previous studies focused primarily on a single cancer type, this study encompassed multiple malignancies, enhancing the generalizability of findings.

Nevertheless, limitations include a modest sample size and lack of longitudinal data. Future studies should aim to validate these findings across larger, more diverse populations and assess biomarker dynamics throughout cancer progression and treatment.

Salivary nitrite and uric acid are promising non-invasive biomarkers for cancer detection, with nitrite demonstrating superior diagnostic accuracy. Incorporating salivary biomarker analysis into routine clinical practice could facilitate early detection, particularly in low-resource environments. Further studies with larger cohorts and varied cancer types are recommended to validate and refine these preliminary findings.

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