Evaluation of serum and salivary C-reactive protein for diagnosis of late-onset neonatal sepsis: A single center cross-sectional study

Objective: To evaluate the diagnostic utility of salivary C-reactive protein (CRP) and its potential correlation with serum CRP levels in full-term neonates with late-onset sepsis (LOS).

Methods: This cross-sectional study included 90 neonates assigned to three equal groups: culture proven LOS, clinical LOS and a control group. Clinical findings and routine laboratory data including complete blood pictures and blood culture results were documented. Highly sensitive serum CRP was measured according to hospital protocol, while salivary CRP levels were measured using enzyme-linked immunosorbent assay.

Results: The median serum CRP was significantly higher in septic neonates compared to controls (p < 0.001). For serum CRP, the optimum cut-off value for LOS diagnosis was found to be 7.2 mg/L with sensitivity, specificity, positive and negative predictive values of 91, 100, 100, and 85.7%, respectively. No significant difference was observed in levels of salivary CRP among the 3 study groups (p = 0.39). No correlation was found between the levels of salivary and serum CRP (r = 0.074, p = 0.49).

Conclusion: Serum CRP, at a cut-off value of 7.2 mg/L, exhibited a high specificity and positive predictive value in LOS diagnosis, whereas salivary CRP levels weren't significantly different between the 3 study groups nor did they predict abnormal serum CRP thresholds in newborns with sepsis.