Saliva-based monitoring of chronic kidney disease: comparative evaluation of three collection methods for creatinine, urea, calcium, and PTH.
Level 4 - case-series / case-control
Cross-sectional comparative biomarker study with healthy controls
PubMed 42230865 · doi:10.1038/s41598-026-54228-2
What was done
Paired saliva and serum samples were collected from 47 healthy adults and 47 chronic kidney disease (CKD) patients. Saliva was obtained using three methods: passive drool, Salivette, and cotton roll. Creatinine, urea, calcium, and parathyroid hormone (PTH) were measured with standardized assays. Researchers assessed inter-method agreement with intraclass correlation coefficients (ICC) and Bland-Altman analysis, and evaluated saliva-serum relationships using correlation analyses and linear regression.
What was found
Salivary creatinine, urea, and PTH had moderate agreement across collection methods (average-measure ICCs higher than single-measure), whereas calcium showed poor agreement. Limits of agreement were narrower for creatinine and urea (notably using cotton roll and passive drool) compared to calcium and PTH. Salivary creatinine and urea correlated moderately to strongly with serum levels, highest with cotton roll (creatinine ρ = 0.584; urea ρ = 0.648), and predicted serum levels in CKD patients (R² = 0.214 for creatinine, R² = 0.339 for urea). Calcium and PTH showed weak correlations and minimal predictive value.
Why it matters
Salivary creatinine and urea collected via non-invasive means such as cotton rolls or passive drool show potential as supplementary tools for renal monitoring, though saliva is unsuitable for tracking calcium or PTH.
Limits
The study is cross-sectional with a small sample size (47 CKD patients, 47 controls). The predictive value for creatinine and urea was only modest (R² ≤ 0.339), and the abstract does not report CKD stages, patient comorbidities, hydration status, or clinical diagnostic thresholds.
Cited by
- contradicts Saliva normally has a higher concentration of calcium than blood serum.