Cord Blood Acute Phase Reactants Predict Early Onset Neonatal Sepsis in Preterm Infants

Abstract

Background: Early onset sepsis (EOS) is a major cause of morbidity and mortality in preterm infants, yet diagnosis remains inadequate resulting in missed cases or prolonged empiric antibiotics with adverse consequences. Evaluation of acute phase reactant (APR) biomarkers in umbilical cord blood at birth may improve EOS detection in preterm infants with intrauterine infection.

Methods: In this nested case-control study, infants (29.7 weeks gestation, IQR: 27.7-32.2) were identified from a longitudinal cohort with archived cord blood and placental histopathology. Patients were categorized using culture, laboratory, clinical, and antibiotic treatment data into sepsis groups: confirmed sepsis (cEOS, n = 12); presumed sepsis (PS, n = 30); and no sepsis (controls, n = 30). Nine APRs were measured in duplicate from cord blood using commercially available multiplex immunoassays (Bio-Plex Pro™). In addition, placental histopathologic data were linked to biomarker results.

Results: cEOS organisms were Escherichia coli, Streptococcus agalactiae, Proteus mirabilis, Haemophilus influenzae and Listeria monocytogenes. C-reactive protein (CRP), serum amyloid A (SAA), haptoglobin (Hp), serum amyloid P and ferritin were significantly elevated in cEOS compared to controls (p<0.01). SAA, CRP, and Hp were elevated in cEOS but not in PS (p<0.01) and had AUCs of 99%, 96%, and 95% respectively in predicting cEOS. Regression analysis revealed robust associations of SAA, CRP, and Hp with EOS after adjustment for covariates. Procalcitonin, fibrinogen, α-2-macroglobulin and tissue plasminogen activator were not significantly different across groups. Placental acute inflammation was associated with APR elevation and was present in all cEOS, 9 PS, and 17 control infants.

Conclusion: This study shows that certain APRs are elevated in cord blood of premature infants with EOS of intrauterine origin. SAA, CRP, and Hp at birth have potential diagnostic utility for risk stratification and identification of infants with EOS.

Fig 1. Study design and patient selection.

Of 1100 enrolled infants, 12 had confirmed early onset sepsis (cEOS: positive blood culture with bacterial neonatal sepsis pathogen within 72 HOL and received antibiotic treatment ≥5 days). Presumed sepsis (PS) subjects were treated for early infection with antibiotics within first 72 HOL, had no positive sterile site culture during NICU stay, and had ≥2 abnormal lab criteria (↓ANC, ↑ I:T ratio, ↑CRP). Late onset sepsis (LOS) subjects had positive blood culture after 72 HOL treated with antibiotics. Control patients had no sterile site culture or antibiotic course >4 days throughout hospitalization. Patients with ≥2 infection episodes were excluded. PS, LOS and control patients were frequency matched to cEOS patients within target gestational age and birth weight ranges (±3 wks and ±400 gms). Infants were randomly selected from the group fitting GA/BW criteria.

Fig 2. Acute phase reactant levels in sepsis groups.

Box and whisker plots displaying distribution of 9 APR biomarkers (SAA, CRP, Hp, ferritin, SAP, PCT, tissue plasminogen activator, fibrinogen, α-2-macroglobulin) in each sepsis category. *Indicates significant difference in APR values between cEOS and control groups. **Indicates significant difference in APR values between cEOS and PS groups.

Fig 3. Serum amyloid A, C-reactive protein, and haptoglobin levels in sepsis groups by AI.

Box and whisker plots displaying distribution of 3 APR biomarkers (SAA, CRP, Hp) in each sepsis category with and without fetal AI [bottom row] and any placental AI (maternal and/or fetal) [top row].

Fig 4. Receiver operating characteristic curves.

ROC curves for serum amyloid A, C-reactive protein, and haptoglobin. The above acute phase reactants had areas under the curve of >95% for prediction of EOS.