Complement levels and their diagnostic utility in neonatal sepsis.

BACKGROUND

This study evaluated the diagnostic value of complement levels in neonatal sepsis and their roles in disease progression.

METHODS

This diagnostic accuracy study, conducted in Guangdong Province, China (January 2021-February 2022), involved 41 neonates with sepsis and 41 controls matched by sex and gestational age. Cases included neonates with culture-positive or clinically diagnosed sepsis, while controls consisted of neonates hospitalized for non-septic conditions, confirmed by negative blood cultures. Ten complement components (C1q, C3, C3c, C3b, C4, C5, C5a, H, B, mannose-binding lectin [MBL]) were quantified using residual specimens from routine clinical tests. Descriptive statistics, logistic regression, ROC curve analysis, and correlation assessments were introduced in this study.

RESULTS

The neonatal sepsis group had significantly higher levels of C3c (0.68 vs. 0.49 ng/mL, P = 0.007) and MBL (518.81 vs. 397.06 pg/mL, P < 0.001) compared to controls. In contrast, C5a levels were significantly lower in neonates with sepsis (51.18 vs. 57.25 ng/mL, P = 0.042). C5a demonstrated limited individual performance (AUC = 0.63, 95% CI: 0.51-0.75; sensitivity = 65.9%, specificity = 65.9% at 55.63 ng/mL), while MBL showed moderate accuracy (AUC = 0.75, 95% CI: 0.64-0.85; specificity = 90.2%, sensitivity = 53.7% at 512.86 pg/mL). Notably, their combined C5a + MBL indicator achieved exceptional discrimination (AUC = 0.92, 95% CI: 0.85-0.99) with 85.4% sensitivity and 97.6% specificity, yielding 97.2% positive predictive value (PPV) and 87.0% negative predictive value (NPV).Positive correlations were found between C4 levels and C-reactive protein (CRP), and C3 levels and neutrophil percentage (Neut%), while negative correlations were observed between C5 and MBL levels and total cholesterol (TCH).

CONCLUSIONS

This study highlights the diagnostic significance of combined C5a + MBL indicator in neonatal sepsis and underscores the association between complement levels and disease progression.