Neonatal sepsis, especially late-onset sepsis (LOS) continues to be a major source of morbidity and mortality in very- low-birth-weight infants (VLBW <1500 g) or pre-terms. The International Pediatric Sepsis Consensus Conference defined sepsis as “the systemic inflammatory response syndrome in the presence or as a result of a suspected or proven infection” [a]. Major causes of infection include bacteria such as coagulase-negative Staphylococci and multiple other aggressive pathogens, such as the Klebsiella-Enterobacter-Serratia group, Pseudomonas, and Candida species. Survivors suffer from neuro-developmental impairment during at least the first 2 years of life [b].
Therapy with antibiotics is the standard of care. Based on the timing of the infection newborn sepsis has been classified into early-onset sepsis (EOS) and late-onset sepsis (LOS). Early-onset sepsis (EOS) is discriminated from late-onset sepsis (LOS) depending on whether is present within or after the first 72 h of life, respectively [c,i].
Sepsis biomarkers in neonatal care
C-reactive protein (CRP) is generally considered an inflammation/infection marker for diagnosis of sepsis used in addition to bloodculture, but is not very specific. In newborns, procalcitonin (PCT) levels show a physiologic increase 24-48 hours after birth and decreases to normal levels after 3 days. PCT increases in hypoxia, respiratory distress syndrome (RDS) and hemodynamic instability, which lowers its specifity for sepsis. The proinflam-matory cytokine IL-6 increases quickly after onset of the infection, but returns to undetectable levels during 24 h.
D-Dimer is generated by thromboembolic situations that are not necessarily linked to sepsis. It is not a specific sepsis marker but may be a useful indicator of the coagulation status of the infant and the requirement for anticoagulant therapy [d,e]. Presepsin shows promising performance in diagnosing sepsis in neonates and prognosing severity of the disease.
Presepsin biochemistry in neonatives
Presepsin (sCD14-ST) is a specific and sensitive biomarker for sepsis. Presepsin levels rise after 2 h, earlier than IL-6 and PCT, with a peak 3 h after onset of the infection and a decline after 4-8 hours [f]. Presepsin can be used for monitoring of treatment with antibiotics and can show effectiveness of antibiotics. It is a reliable tool for early diagnosis of sepsis caused by Gram-positive and Gram-negative bacteria or fungi [g] and is accurate in neonatal sepsis using special cut off values which are higher than in adults [h].
Presepsin secretion is linked to the Toll Like 4 Receptor (TLR) and its sensor function is well developed in newborns. Levy et al. [k] described in preterm and full-term neonates signiﬁcantly higer expression levels of TLR4 on peripheral blood monocytes both at baseline and after LPS stimulation, compared to adults. In the same study, they also observed significantly higher CD14 expression at baseline and after LPS stimulation in full-term neonates compared to adults.
Presepsin in neonatal sepsis (LOS and EOS)
The diagnostic validity of Presepsin in neonatal sepsis has been evaluated in numerous clinical studies. Pugni et al. [l] enrolled 684 healthy neonates (484 born at term and 200 preterm) for evaluation of reference ranges for Presepsin. Presepsin median value in term infants was 604 pg/mL whereas in preterm infants the Presepsin median value was slightly higher (620 pg/mL). The normal reference ranges of Presepsin observed were higher than those seen in healthy adults. The Presepsin level was not affected by gender, ethnicity, mode of delivery, small for gestational age (GA), twin, maternal fever/elevated CRP, and stained amniotic fluid . Reliable reference values are important for adequate diagnostic accuracy. Based on current clinical study results, most factors affecting C-reactive protein and procalcitonin levels do not affect Presepsin levels. Presepsin can discriminate between infections and non-infectious inflammatory conditions.
Poggi et al. [h] prospectively studied newborns ≤32 weeks gestational age with LOS (n=19) and noninfected controls (n=21) at 4 to 60 days postnatal age. At enrollment and at day 1, 3 and 5 the biomarkers CRP, PCT and Presepsin were measured in the LOS group with single measurements of Presepsin in the control group. Presepsin was higher in the LOS than in the control group at enrollment (1295 vs. 562 ng/L) and was elevated throughout the evaluation period. The Receiver-Operating-Characteristic curve (ROC) for Presepsin at enrollment showed specifity of 94% and sensitivity of 54% for IL-6, 78% sensitivity and 70% specifity for Il-8, sensitivity of 97,5% and specifity of 88,9% for PCT. Presepsin showed 100% sensitivity and 94% specifity (Fig. 1). Other studies showed lower sensitivity and specifity for CRP, PCT and IL-6. These data support the potential role for Presepsin as a marker for monitoring the response to antibiotic treatment in preterm infants.
Xiao et al. [g] evaluated 42 neonates with hematosepsis, 54 new-borns with nonhematosepsis, 44 noninfectious SIRS neonates (n=140) and 53 healthy controls. Before treatment Presepsin, CRP, white blood cells (WBC) and PCT was determined. Furthermore, APACHE-II score was assigned for all samples before and after treatment. Presepsin levels were significantly higher in neonatal hematosepsis than in noninfectious SIRS or control group. Interestingly, Presepsin levels were positively correlated with APACHE-II score. During treatment with antibiotics, Presepsin levels decreased together with APACHE-II score, PCT, CRP and WBC. Presepsin showed an Area under the curve (AUC) value of 0,942 with a corresponding sensitivity of 95,2% and specifity of 84,9%, respectively. The calculated cut off value was 786 pg/ml [g, Fig. 2].
Presepsin is a biomarker for early identification and disease valuation in newborns hematosepsis infection with Gram-positive and Gram-negative bacteria with a high diagnostic value compared to other laboratory indexes like CRP, PCT and WBC [g, Tab. 1].
Diagnostic accuracy of Presepsin, cut off values and blood sampling in neonates
Bellos et al. [j] and Ruan et al. [w] recently published two meta-analysis´ summarizing cut off values of Presepsin for exclusion of sepsis in neonates. Furthermore, Ruan et al. showed superior diagnostic accuracy of Presepsin for neonatal sepsis diagnosis when compared with simultaneous use of CRP and PCT (AUC = 0,99 vs AUC = 0,96) whereas Bellos et al. recommended the use of three different threshold values which are in good alignment with 14 clinical study publications shown in Tab. 2. Recommended cut off values were 650, 650-850, 850 pg/ml with corresponding AUC of 0,9634, 0,9915, and 0,9681, respectively. These findings are comparable with the summary listed in Tab. 3. A reliminary cut off value of ≤650 pg/ml for exclusion of sepsis seems to be appropriate for neonates. Presepsin values ≥850 pg/ml indicate a bacterial infection. A grey zone from 650-850 pg/ml still remains to be validated by further studies. Blood sampling for Presepsin measurements can be taken on the first day of sepsis prior to the initiation of empirical antibiotic therapy, 12, 24 and 48 hours of age [i].