New reference ranges of procalcitonin excluding respiratory failure in neonates.

Background Existing reference data on serum procalcitonin (PCT) in neonates include the effects of respiratory disorders commonly occurring during birth. We aimed to determine new 95% reference intervals in neonates after excluding the influence of respiratory failure at birth, and to investigate the effects of gestational age (GA) and respiratory condition at birth on postnatal transient serum PCT elevation. Methods Samples were obtained from term and preterm neonates during the first 3 days of life. Neonates were classified into reference, respiratory failure, and bacterial infection groups. In the reference group, the correlation between PCT level and GA was investigated. Results The median PCT level within the 95% range 12-36 h after birth was 1.05 ng/mL (0.14-4.39) in term neonates (143 samples) and 1.01 ng/mL (0.15-4.44) in preterm neonates (95 samples). There was no correlation between GA and serum PCT level during 1-48 h after birth. There was a significant difference in median serum PCT level during 12-36 h after birth between the respiratory failure (9.56 ng/mL) and bacterial infection (49.82 ng/mL) groups in preterm neonates but no difference between term neonates (respiratory failure 6.83 ng/mL, and bacterial infection 7.43 ng/mL). Conclusions Respiratory failure is the main effector for the transient elevation in serum PCT levels at 3 days of life. After excluding the influence of respiratory failure, the chronological pattern and range were very similar between term and preterm neonates. Procalcitonin can be useful for clinicians in distinguishing bacterial infection from respiratory failure, aiding decisions on appropriate antibiotic use.