Salivary phosphate: A promising non-invasive biomarker for oral and systemic disease screening

Saliva has emerged as an attractive diagnostic fluid due to its non-invasive accessibility and its ability to reflect both local oral and systemic physiological states. Among salivary analytes, phosphate has gained increasing attention as a potential biomarker because of its essential role in musculoskeletal integrity, gastrointestinal function, renal homeostasis, and cellular metabolism. Unlike many circulating biomarkers, salivary phosphate is regulated through mechanisms that are partially independent of plasma phosphate levels, indicating that it may capture early biochemical and pathophysiological changes. Recent advances in the molecular characterization of salivary phosphate transporters, particularly, involving the type IIb sodium phosphate cotransporter (NaPi-IIb) and associated signaling pathways, have further implicated salivary phosphate in the pathogenesis of chronic inflammatory and metabolic disorders. Growing evidence also indicates that alterations in salivary phosphate levels are associated with oral diseases, such as periodontitis, and may also reflect broader systemic conditions, including metabolic dysregulation, renal dysfunction, and inflammation driven disease processes. In this review, we highlight current knowledge on the biological regulation of salivary phosphate and summarize available analytical technologies for its accurate and reproducible quantification. We further explore oral and systemic disease settings where salivary phosphate screening may be clinically informative and address key challenges in standardization, clinical validation, and integration into routine diagnostic workflows. Collectively, this article highlights the emerging diagnostic potential of salivary phosphate and outlines future directions for its application in oral and systemic disease detection.