Procalcitonin in pediatrics: overview and challenge

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.

Usefulness of the procalcitonin test in young febrile infants between 1 and 3 months of age

Purpose

To study the usefulness of the procalcitonin (PCT) test in young febrile infants between 1 and 3 months of age.

Methods

We evaluated the medical records of 336 febrile infants between 1 and 3 months of age who visited the Emergency Department or outpatient department of Samsung Changwon Hospital from May 2015 to February 2017, and analyzed the clinical characteristics between infants in the serious bacterial infection (SBI) group and non-SBI group.

Results

Among the 336 infants, 38 (11.3%) had definitive SBI (bacteremia, n=3; meningitis, n=1; urinary tract infection, n=34). The mean PCT (6.4±11.9 ng/mL) and C-reactive protein (CRP) level (3.8±2.6 mg/dL), and the absolute neutrophil count (ANC) (6,984±4,675) for patients in the SBI group were significantly higher than those for patients in the non-SBI group (PCT, 0.3±1.2 ng/mL; CRP, 1.3±1.6 mg/dL; ANC, 4,888±3,661). PCT had lower sensitivity (43.6%), but higher specificity (92.6%) and accuracy (86.9%) than CRP (92.3%, 25.3%, and 33.0%) for identifying SBI. The area under the receiver operating characteristic curves (AUCs) for definitive SBI were PCT 77.0%, CRP 80.8%, WBC 56.8%, ANC 67.8%, and PLT 48.1%. The AUCs for definitive SBI were PCT+CRP 85.4%, PCT+WBC 77.2%, PCT+ANC 81.3%, CRP+WBC 80.1%, and CRP+ANC 81.6%.

Conclusion

Our results suggest that the PCT test or a combination of PCT and CRP tests is a more accurate and specific biomarker to detect and rule out SBIs.

Early-Onset Neonatal Sepsis: Still Room for Improvement in Procalcitonin Diagnostic Accuracy Studies

To perform a systematic review assessing accuracy and completeness of diagnostic studies of procalcitonin (PCT) for early-onset neonatal sepsis (EONS) using the Standards for Reporting of Diagnostic Accuracy (STARD) initiative.EONS, diagnosed during the first 3 days of life, remains a common and serious problem. Increased PCT is a potentially useful diagnostic marker of EONS, but reports in the literature are contradictory. There are several possible explanations for the divergent results including the quality of studies reporting the clinical usefulness of PCT in ruling in or ruling out EONS.We systematically reviewed PubMed, Scopus, and the Cochrane Library databases up to October 1, 2014. Studies were eligible for inclusion in our review if they provided measures of PCT accuracy for diagnosing EONS. A data extraction form based on the STARD checklist and adapted for neonates with EONS was used to appraise the quality of the reporting of included studies.We found 18 articles (1998-2014) fulfilling our eligibility criteria which were included in the final analysis. Overall, the results of our analysis showed that the quality of studies reporting diagnostic accuracy of PCT for EONS was suboptimal leaving ample room for improvement. Information on key elements of design, analysis, and interpretation of test accuracy were frequently missing.Authors should be aware of the STARD criteria before starting a study in this field. We welcome stricter adherence to this guideline. Well-reported studies with appropriate designs will provide more reliable information to guide decisions on the use and interpretations of PCT test results in the management of neonates with EONS.

Procalcitonin in pediatrics

Over the past two decades, the body of literature on the clinical usefulness of procalcitonin (PCT) in adults has grown rapidly. Although this approach has led to increased insight, it has also prompted debate regarding its potential use in diagnosis and management of severe infection. Clinicians, however, are less familiar with the use of PCT in pediatric populations. In this review, we examine PCT as a marker of severe clinical pediatric conditions including its role in systemic inflammation, infection, and sepsis.

Evaluation of serum procalcitonin levels for diagnosis of secondary bacterial infections in visceral leishmaniasis patients

Abstract. Secondary bacterial infections are a major complication and cause of death in children with visceral Leishmaniasis (VL). Thus, early diagnosis of bacterial infections is an important step in the treatment of patients with VL. The goal of this study was to determine if serum procalcitonin (PCT) could be used as a diagnostic marker of secondary bacterial infections in VL patients. Serum PCT was measured in 35 hospitalized patients with VL before treatment and after defervescence. The level was higher than normal (> 0.5 ng/mL) in 72% (25) of the patients. Twelve (34%) of 35 patients had secondary bacterial infections with PCT levels ranging from 0.1 to 12.29 ng/mL, and those without secondary bacterial infections (23) had PCT levels ranging from 0.1 to 14.58 ng/mL. The results suggest that PCT levels increase significantly in most VL patients but are not correlated with the presence of secondary bacterial infections.

Sepsis in the neonate

In the neonatal intensive care unit, critical care nurses who are not advanced practice nurses cannot make the medical diagnosis of infection/sepsis in the neonate. Even so, the critical care nurse has a critical role in dealing with sepsis infection. The nurse must (1) have a high index of suspicion about the risk of infection, (2) be able to recognize septic/infected newborns, (3) report related concerns to the physician or advanced practice nurse, and (4) advocate on behalf of the infant to ensure a timely diagnostic workup and empiric antibiotics. This article is a guide for understanding issues related to sepsis in the neonatal intensive care unit.

Procalcitonin as a marker of nosocomial infections in the neonatal intensive care unit

OBJECTIVE

To determine accuracy of procalcitonin concentrations for diagnosing nosocomial infections in critically ill neonates.

DESIGN

Case-control study.

SETTING

Neonatal intensive care unit of a teaching hospital.

PATIENTS

Twenty-three neonates with nosocomial infection. Four controls matched for duration of hospital stay and birth date were chosen for each case patient.

MEASUREMENTS AND RESULTS

PCT concentrations were measured by the LUMItest procalcitonin kit at onset of signs of infection and after recovery. Range of PCT concentrations (ng/ml) was 2.0 to 249.1 in case patients and 0.08 to 1.0 in controls (sensitivity and specificity, 100%). PCT values returned to normal (<1.0 ng/ml) by day 3 to 7 of appropriate antibiotic therapy.

CONCLUSIONS

Measurement of PCT concentrations may be useful for early diagnosis and monitoring of infectious complications in neonates during their stay in the neonatal intensive care unit.

The role of procalcitonin as a predictor of nosocomial sepsis in preterm infants

AIM

To assess the role of procalcitonin in detecting nosocomial sepsis in preterm infants, after the onset of clinical symptoms.

SUBJECTS

100 preterm infants, 24-36 wk of gestation, were followed from the age of 3 d until discharge. Procalcitonin and C-reactive protein (CRP) levels were measured within 3 d of sepsis workup events.

RESULTS

141 blood samples were drawn from 36 infants during 85 episodes of sepsis workup performed between 4 and 66 d of life. Of these episodes, 51 (60%) were not a result of documented sepsis and thereby served as the negative comparison group. Median procalcitonin levels were higher in the septic group compared with the non-septic group at the time of the sepsis workup (2.7 vs 0.5 ng/ml, p=0.003), at 1-24 h after the sepsis workup (4.6 vs 0.6 ng/ml, p=0.003), and at 25-48 h (6.9 vs 2.0 ng/ml, p=0.016). Using high cutoff levels, both procalcitonin (2.3 ng/ml) and CRP (30 mg/l) had high specificity and positive predictive value (97%, 91% and 96%, 87%, respectively) but low sensitivity (48% and 41%, respectively) to detect sepsis. Areas under the ROC curve for procalcitonin and CRP were 0.74 and 0.73, respectively.

CONCLUSION

Procalcitonin >2.3 ng/ml or CRP >30 mg/l indicates a high likelihood for neonatal sepsis, and antibiotic therapy should be continued even in the presence of sterile cultures.

Procalcitonin in preterm infants during the first few days of life: introducing an age related nomogram

OBJECTIVE

To determine normal concentrations of procalcitonin in preterm infants shortly after birth and to assess its accuracy in detecting bacterial infection.

METHODS

Blood samples of 100 preterm infants were prospectively drawn during the first 4 days of life for determination of procalcitonin concentration. Infants were classified into four groups according to their sepsis status.

RESULTS

Mean (SD) gestational age and birth weight were 32 (2.9) weeks and 1682 (500) g respectively. A total of 283 procalcitonin concentrations from healthy infants were plotted to construct nomograms of physiologically raised procalcitonin concentration after birth, stratified by two groups to 24-30 and 31-36 weeks gestation. The peak 95th centile procalcitonin concentration was plotted at 28 hours of age; values return to normal after 4 days of life. Only 12 infants were infected, and 13 of their 16 procalcitonin concentrations after birth were higher than the 95th centile, whereas samples taken at birth were lower. In a multivariable analysis, gestational age, premature rupture of membrane, and sepsis status influenced procalcitonin concentration independently, but maternal infection status did not.

CONCLUSIONS

The suggested neonatal nomograms of preterm infants are different from those of term infants. Procalcitonin concentrations exceeding the 95th centile may be helpful in detecting congenital infection, but not at birth.

Predictive value of procalcitonin for the diagnosis of bowel strangulation

Intestinal obstruction is responsible for 3% of admissions to hospital emergency surgical departments, but it is difficult to distinguish simple obstruction from strangulation. Simple criteria for this distinction are sought. In this experimental study, procalcitonin, a known marker of bacterial inflammation, was used to detect strangulation. The predictive value of procalcitonin for small bowel strangulation was evaluated. Thirty male New Zealand rabbits (mean weight: 3.0 kg) were divided into three groups. In the first (control) group, only laparatomy was performed. In the second group, simple obstruction was created by ligating a 10-cm distal ileum segment. In the third group, distal strangulation was created by ligating a 10-cm distal ileum segment with the mesentery. Blood (1 cc) was taken from the right auricular vein of each animal for measuring the procalcitonin level. In both the control group and the simple obstruction group the procalcitonin levels were normal. In the strangulation group, elevation of procalcitonin was detected after 30 minutes, and the elevation was statistically significant at 120th minute compared with the control and simple obstruction groups. In patients with small bowel obstruction, measurement of procalcitonin levels is easy to perform and can be used in the follow-up. A more extensive clinical study is needed to evaluate the accuracy of the test as a marker.

Immunologic markers in the neonatal period: diagnostic value and accuracy in infection

Diagnosis of early-onset neonatal infection has led to the development of several screening tests including C-reactive protein, a very commonly used marker, and cytokines (mainly interleukin-6 and -8), alone or in combination with C-reactive protein, based on the premise that their increases in response to infection may precede that of C-reactive protein. In recent years the search for diagnostic tests has turned to procalcitonin, a propeptide of calcitonin, which appears to be a promising marker of infection in newborn infants. Additionally, specific leukocyte cell surface antigens (mainly CD11b and CD64), detected by flow cytometry, are evaluated as markers of neonatal infection, since their expression on the cell membrane increases in substantial quantities after leukocyte activation by bacteria or their cellular products. This review aims to examine the role of these newly available immunologic indices and to assess their validity as diagnostic markers of infection during the neonatal period.

Procalcitonin in pediatric emergency departments for the early diagnosis of invasive bacterial infections in febrile infants: results of a multicenter study and utility of a rapid qualitative test for this marker

BACKGROUND

Procalcitonin (PCT) is a potentially useful marker in pediatric Emergency Departments (ED). The basic objectives of this study were to assess the diagnostic performance of PCT for distinguishing between viral and bacterial infections and for the early detection of invasive bacterial infections in febrile children between 1 and 36 months old comparing it with C-reactive protein (CRP) and to evaluate the utility of a qualitative rapid test for PCT in ED.

METHODS

Prospective, observational and multicenter study that included 445 children who were treated for fever in pediatric ED. Quantitative and qualitative plasma values of PCT and CRP were correlated with the final diagnosis. To obtain the qualitative level of PCT the BRAHMS PCT-Q rapid test was used.

RESULTS

Mean PCT and CRP values in viral infections were 0.26 ng/ml and 15.5 mg/l, respectively. The area under the curve obtained for PCT in distinguishing between viral and bacterial infections was 0.82 (sensitivity, 65.5%; specificity, 94.3%; optimum cutoff, 0.53 ng/ml), whereas for CRP it was 0.78 (sensitivity, 63.5%; specificity, 84.2%; optimum cutoff, 27.5 mg/l). PCT and CRP values in invasive infections (PCT, 24.3 ng/ml; CRP 96.5 mg/l) were significantly higher than those for noninvasive infections (PCT, 0.32 ng/ml; CRP, 23.4 mg/l). The area under the curve for PCT was 0.95 (sensitivity, 91.3%; specificity, 93.5%; optimum cutoff, 0.59 ng/ml), significantly higher (P < 0.001) than that obtained for CRP (0.81). The optimum cutoff value for CRP was >27.5 mg/l with sensitivity and specificity of 78 and 75%, respectively. In infants in whom the evolution of fever was <12 h (n = 104), the diagnostic performance of PCT was also greater than that of CRP (area under the curve, 0.93 for PCT and 0.69 for CRP; P < 0.001). A good correlation between the quantitative values for PCT and the PCT-Q test was obtained in 87% of cases (kappa index, 0.8). The sensitivity of the PCT-Q test (cutoff >0.5 ng/ml) for detecting invasive infections and differentiating them from noninvasive infections was 90.6%, with a specificity of 83.6%.

CONCLUSIONS

PCT offers better specificity than CRP for differentiating between the viral and bacterial etiology of the fever with similar sensitivity. PCT offers better sensibility and specificity than CRP to differentiate between invasive and noninvasive infection. PCT is confirmed as an excellent marker in detecting invasive infections in ED and can even make early detection possible of invasive infections if the evolution of the fever is <12 h. The PCT-Q test has a good correlation with the quantitative values of the marker.

Procalcitonin, C-reactive protein, and endotoxin after bone marrow transplantation: identification of children at high risk of morbidity and mortality from sepsis

We prospectively evaluated the capacity of serum procalcitonin (PCT), compared with serum levels of C-reactive protein (CRP) and endotoxin, to identify children at high risk for mortality from sepsis after BMT. Of 47 pediatric bone marrow transplantation patients studied, 22 had an uneventful course post-transplant (Group 1), 17 survived at least one septic event (Group 2), and eight died from multiorgan failure (MOF) following septic shock (Group 3). Median concentrations of PCT over the course of the study were 1.3, 15.2, and 102.8 ng/ml, respectively, in each of the three groups (P<0.002 for each comparison). Median concentrations of CRP were 91, 213, and 260 mg/l, respectively (P<0.001 for Group 1 vs Group 2 and Group 3; P=NS for Group 2 vs Group 3). Median concentrations of endotoxin were 0.21, 0.30, and 0.93 U/l, respectively (P=NS for each comparison). Median concentrations of PCT, in contrast to serum CRP and endotoxin, correlated with the severity of sepsis (8.2 ng/ml in 'sepsis' and 22.3 ng/ml in 'severe sepsis', P=0.028) and provided useful prognostic information during septic episodes.

Kinetics of procalcitonin, interleukin 6 and C-reactive protein after cardiopulmonary-bypass in children

Cardiopulmonary bypass induces a generalized inflammatory response, with fever and leukocytes, which is difficult to differentiate from an infection. Recently, procalcitonin has been proposed as an early and specific marker of bacterial infection. The influence of cardiopulmonary bypass on production of procalcitonin, therefore, must be assessed before considering this molecule as a valuable marker of infection after cardiac surgery in children. With this in mind, we measured levels of procalcitonin, interleukin 6, and C-reactive protein before and 6h, 1, 3 and 5 days after cardiopulmonary bypass, in 25 children undergoing cardiac surgery. Cardiopulmonary-bypass induced a transient increase in procalcitonin, with a peak at 24 h, with a median of 1.13 microg/l, a 25th and 75th interquartile of 0.68-2.25, and a p value of less than 0.001. The value had returned to normal in the majority of the children by the third day after surgery. Peak values correlated with the duration of cardiopulmonary-bypass, with a r-value of 0.58 and a p value of 0.003; cross-clamp time, with a r-value of 0.62 and a p value of 0.001; days of mechanical ventilation, with a r-value of 0.62 and a p value of 0.001; and days of stay in intensive care, with a r-value of 0.68, and a p value of 0.0003. The value returned to normal after 3 days in 83% of the patients. Levels of interleukin 6 and C-reactive protein also increased significantly after surgery, and remained elevated for up to 5 days. Thus, in contrast to other markers, levels of procalcitonin in the serum are only slightly and transiently influenced by cardiopulmonary bypass, and may prove to be useful in the early recognition of an infection subsequent to cardiopulmonary bypass.

C-reactive protein, interleukin-6, and procalcitonin in the immediate postnatal period: influence of illness severity, risk status, antenatal and perinatal complications, and infection

BACKGROUND

Studies of the diagnostic accuracy of most laboratory tests for early-onset neonatal sepsis have yielded variable results. We investigated whether some of this variation might be attributable to differences in population baseline severity and risk status as well as to specific ante- and perinatal variables, independent of the presence of neonatal infection.

METHODS

The Score for Neonatal Acute Physiology (SNAP) was used to define illness severity, with SNAP Perinatal Extension (SNAP-PE) used to define the combined physiologic and perinatal mortality risk. A total of 134 ill newborns (19 with early-onset infection and 115 with no infection) were available for simultaneous analysis of the association of SNAP, SNAP-PE, and maternal and perinatal variables with C-reactive protein (CRP), interleukin-6 (IL-6), and procalcitonin (PCT) concentrations at birth and at 24 and 48 h of life.

RESULTS

Early-onset neonatal infection was associated with significant increases in CRP, IL-6, and PCT concentrations at all three time points, independent of illness severity. However, among babies without infection, higher SNAP and SNAP-PE scores were associated with higher IL-6 concentrations at birth. Certain maternal or perinatal variables altered IL-6 and PCT values in the infected as well as in the uninfected neonates. However, if different cutoff points were used at any of the three neonatal ages, PCT sensitivity and specificity were greater than those of CRP or IL-6.

CONCLUSIONS

Illness severity and risk status are unlikely to interfere with the use of CRP and PCT for detection of early-onset neonatal sepsis. In contrast, the diagnostic value of IL-6 at birth may be altered by physiologic severity and risk indexes. The reliability of CRP, IL-6, and PCT for the diagnosis of early-onset neonatal infection requires specific cutoff values for each evaluation time point over the first 48 h of life.

Procalcitonin-reduced sensitivity and specificity in heavily leucopenic and immunosuppressed patients

Procalcitonin (PCT) has proven to be a very sensitive marker of sepsis for non-leucopenic patients. Little is known about its relevance in immunosuppressed and leucopenic adults. Four hundred and seventy-five PCT determinations were carried out in 73 haematological patients: on 221 occasions the white blood cell (WBC) count was < 1.0 x 10(9)/l and on 239 occasions it was > 1.0 x 10(9)/l leucocytes. Patients were classified as: non-systemic infected controls (n = 280), patients with bacteraemia (n = 32), sepsis (n = 30), severe sepsis (n = 3), septic shock (n = 3) and systemic inflammatory response syndrome (SIRS) (n = 62). When the WBC count was > 1.0 x 10(9)/l, gram-negative bacteria induced higher PCT levels (median 9.4 ng/ml) than gram-positives (median 1.4 ng/ml). In cases with a WBC < 1.0 x 10(9)/l, PCT levels were similar for gram-negative and gram-positive bacteria (1.1 ng/ml versus 0.85 ng/ml). Regardless of the leucocyte count, the median PCT level in bacteraemia cases always remained < 0.5 ng/ml. In heavily leucopenic situations, PCT levels were never > 2 ng/ml even in the sepsis and severe sepsis/septic shock groups, whereas a WBC count > 1.0 x 10(9)/l resulted in median PCT values of 4.1 ng/ml and 45 ng/ml respectively. The positive predictive value for sepsis (cut-off 2 ng/ml) was 93% in cases of WBC count > 1.0 x 10(9)/l, but only 66% in leucopenic conditions. The negative predictive value (cut-off 0.5 ng/ml) was 90% when the WBC count was > 1.0 x 10(9)/l and 63% in leucopenic conditions. Procalcitonin is an excellent sepsis marker with a high positive- and negative-predictive value in patients with WBC count > 1.0 x 10(9)/l, but it does not work satisfactorily below this leucocyte count.

Procalcitonin in paediatric cancer patients: its diagnostic relevance is superior to that of C-reactive protein, interleukin 6, interleukin 8, soluble interleukin 2 receptor and soluble tumour necrosis factor receptor II

Sensitive parameters of inflammation are rare in neutropenic cancer patients. In this study, procalcitonin (PCT), C-reactive protein (CRP), interleukin 6 (IL-6), IL-8, the soluble IL-2 receptor (sIL-2R) and the soluble tumour necrosis factor receptor II (sTNFRII) were evaluated for their diagnostic relevance in febrile episodes of cancer patients. Plasma or serum levels of these parameters were determined in neutropenic children with febrile episodes (n = 122) classified according to both the kind of infection [60 cases of fever of unknown origin (FUO), 28 cases of localized infection, 13 cases of pneumonia, 20 cases of bacteraemia, one case of fungaemia] and the World Health Organization (WHO) score of chemotherapy-induced mucositis. At baseline and during the febrile episodes, the highest levels of all parameters were observed in cases of gram-negative bacteraemia. However, in FUO and localized infections, low or only slightly elevated median levels of all parameters were documented. The degree of chemotherapy-induced mucositis did not influence the value of any parameter. In comparison with the other inflammatory parameters, PCT (optimum cut-off level 0.5 microg/l) was a more sensitive and more specific parameter in the diagnosis of high-risk (gram-negative bacteraemia) and low-risk (FUO) episodes, as well as in the sequential assessment of all febrile neutropenic episodes.

Serum Procalcitonin Concentrations in Term Delivering Mothers and Their Healthy Offspring: A Longitudinal Study

Background: The reported sensitivities and specificities of procalcitonin (PCT) concentrations for the diagnosis of neonatal infection vary widely. A postnatal increase of PCT has been observed in healthy term newborns with a peak at ≈24 h of age, and many questions remain regarding maternal and perinatal factors that may influence the normal PCT kinetics during the immediate postnatal period.

Methods: We prospectively investigated the association between the serum PCT values obtained from 121 mothers at delivery and serum PCT in their healthy, term offspring at birth as well as at 24 and 48 h of age. We also analyzed whether obstetric and perinatal factors would alter maternal and neonatal PCT response.

Results: PCT concentrations in the babies at birth were significantly higher than in the mothers (P &lt;0.0001), with even larger differences at 24 and 48 h of age. None of the variables identified from maternal and perinatal histories had a significant effect on maternal PCT response. In the healthy neonate, the variables that significantly affected the concentration of PCT at birth were the mothers’ PCT (P &lt;0.01), maternal group B streptococcus colonization (P &lt;0.05), and rupture of membranes ≥18 h (P &lt;0.01). The coefficient of linear correlation between the mother’s PCT concentration and that of the baby at birth was 0.32 (P &lt;0.01). The only variable that significantly altered the PCT concentration at both 24 (P &lt;0.01) and 48 (P &lt;0.01) h of age was rupture of membranes ≥18 h. Nonetheless, the PCT response observed during the 48-h period after birth among healthy babies born to mothers with risk factors for infection was well below that reported previously among age-matched neonates with sepsis.

Conclusions: The postnatal increase of PCT observed in the healthy neonate with peak values at 24 h of age most likely represents endogenous synthesis. In estimating the sensitivities and specificities of PCT for diagnosis of sepsis throughout the initial 48 h of life, it is important to consider the normal PCT kinetics and the pattern(s) of PCT response in the healthy neonate.