C reactive protein and procalcitonin: reference intervals for preterm and term newborns during the early neonatal period

Clin Chim Acta. 2011 May 12;412(11-12):1053-9. doi: 10.1016/j.cca.2011.02.020. Epub 2011 Feb 19.


Background: There is still no study evaluating the influence of gestational age (GA) per se on C reactive protein (CRP) and procalcitonin (PCT) reference intervals. We therefore investigated how length of gestation, age (hours), and prenatal and perinatal variables might influence the levels of CRP and PCT. We also determined 95% age-specific reference intervals for CRP and PCT in healthy preterm and term babies during the early neonatal period.

Methods: One blood sample (one observation per neonate) was taken for CRP and PCT from each newborn between birth and the first 4 (for term), or 5 days (for preterm newborns) of life by using a high-sensitive CRP and PCT assays.

Results: Independently of gender and sampling time, GA had a significantly positive effect on CRP, and a significantly negative effect on PCT. Compared with healthy term babies, healthy preterm babies had a lower and shorter CRP response, and, conversely, an earlier, higher, and longer PCT response. CRP reference intervals were affected by a number of pro-inflammatory risk factors.

Conclusions: Age- and GA-specific reference ranges for both CRP and PCT should be taken into account to optimize their use in the diagnosis of early-onset neonatal sepsis.

MeSH terms

  • Adult
  • Blood Chemical Analysis / standards*
  • C-Reactive Protein / analysis*
  • Calcitonin / blood*
  • Calcitonin Gene-Related Peptide
  • Female
  • Humans
  • Infant, Newborn
  • Male
  • Pregnancy
  • Premature Birth / blood*
  • Protein Precursors / blood*
  • Reference Standards
  • Term Birth / blood*
  • Time Factors


  • CALCA protein, human
  • Protein Precursors
  • Calcitonin
  • C-Reactive Protein
  • Calcitonin Gene-Related Peptide