Diagnostic utility of salivary CRP, MPV, NLR, and PLR in neonatal sepsis: a prospective case-control study

Background Neonatal sepsis (NS) continues to be a leading cause of illness and death in newborns. The lack of identifiable clinical indications and inconclusive blood cultures highlights the need for non-invasive biomarkers that can be relied on for early and accurate diagnosis. We aimed to assess reliability of salivary C-reactive protein (CRP), mean platelet volume (MPV), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR) in the diagnosis of NS. Methods A prospective case-control study was conducted on 80 patients; 40 with sepsis by history, clinical picture, laboratory findings and blood culture and 40 controls with no signs of sepsis. Since 1 patient out of 40 in the case group was culture-negative though had intense clinical indicators, so will define case group as “proven sepsis” ( n = 39) and “clinical/suspected sepsis” ( n = 1). For all patients laboratory analysis was performed [blood culture, complete blood count (CBC): neutrophil-lymphocyte ratio (NLR), platelet lymphocyte ratio (PLR), mean platelet volume (MPV) were calculated, serum and salivary C-reactive protein (CRP) analysis]. Results The diagnostic performance for many laboratory indicators was shown to be extremely significant by receiver operating characteristic curve analysis. Salivary CRP showed significant diagnostic value with an AUC of 0.817 at a cut-off of 3.015 mg/L, with 60% sensitivity and 97.5% specificity. MPV had an AUC of 0.947 at a cut-off of 8.45 fl., with 90% sensitivity and 97.5% specificity. Using a cut-off value of 1.715, NLR demonstrated reasonable diagnostic performance with a 62.5% sensitivity and an 85% specificity, and an area under the curve (AUC) of 0.703. With an AUC of 0.617, PLR failed to show any meaningful diagnostic ability. Conclusions As diagnostic indicators for NS, salivary CRP, mean platelet volume, and neutrophil-lymphocyte ratio demonstrated statistically significant differences compared to the control group, demonstrating good specificity and moderate sensitivity. Despite a higher platelet lymphocyte ratio in the NS group, no statistically significant difference was seen between the control and NS groups. Our study possessed several limitations including modest sample size, excluding preterm neonates and lack of serial longitudinal measurements of salivary CRP.