Is procalcitonin to C-reactive protein ratio useful for the detection of late onset neonatal sepsis?

Procalcitonin (PCT) has been reported as a sensitive marker for neonatal bacterial infections. Recently, small numbers of studies reported usefulness of PCT/C-reactive protein (CRP) ratio in detection of infectious conditions in adults. Thus, we conducted this study to evaluate PCT/CRP ratio in late onset neonatal sepsis. Serum PCT and CRP was measured in blood samples from 7 to 60 days after birth in 106 of neonates with late onset sepsis and 212 of controls who were matched with gestational age, postnatal age, birth weight, and gender. Areas under ROC curve (AUC) were calculated, and pairwise comparisons between ROC curves were performed. As a result, CRP (AUC 0.96) showed best performance in detection of sepsis from healthy controls compared with PCT (AUC 0.87) and PCT/CRP ratio (AUC 0.62); CRP > PCT > PCT/CRP ratio in pairwise comparison (p < .001). Both of CRP (AUC 0.94) and PCT (AUC 0.96) were found to discriminate proven sepsis from healthy controls compared with PCT/CRP ratio (AUC 0.54); CRP = PCT > PCT/CRP ratio in pairwise comparison (p < .001). However, in the detection of blood culture proven sepsis from suspected sepsis, PCT (AUC 0.70), and PCT/CRP ratio (AUC 0.73) showed better performance compared with CRP (AUC 0.51); PCT = PCT/CRP ratio > CRP in pairwise comparison (p < .001 and p = .006, respectively). In conclusion, CRP and PCT showed good performance in discrimination between sepsis and healthy controls. However, PCT/CRP ratio seems to be helpful in distinguishing proven sepsis from suspected sepsis together with PCT. Further studies are warranted to elucidate the efficacy of PCT/CRP ratio with enrollment of enough numbers of infants.