Validation of a Noninvasive Physiological Stress and Inflammatory Assessment: Agreement of Salivary and Blood Biomarkers Among First Responders

OBJECTIVE: This study examined blood and saliva cortisol (CORT), interleukin-6 (IL-6), and C-reactive protein (CRP) in first responders to evaluate the accuracy and practicality of using saliva samples in operational contexts. METHODS: Data from 207 first responders were analyzed. Spearman's correlation, simple linear regression models, and Bland-Altman analyses were performed. RESULTS: Salivary CORT ( ρ = 0.713, P < 0.001) closely aligned with blood CORT, accounting for nearly half of the variance and showing narrow Bland-Altman limits. Salivary CRP ( ρ = 0.306, P < 0.001) and IL-6 ( ρ = 0.281, P = 0.007) exhibited weak correlations and poor agreement. CONCLUSIONS: Overall, while salivary CORT is practical for noninvasive monitoring in operational settings, caution is warranted with salivary CRP and IL-6, which need further research as blood substitutes.