Study to evaluate the role of TNFα, IL1β, IL6 in diagnosis and severity assessment of neonatal sepsis among term, appropriate for gestational age newborn. Perinatal Journal 2021;29(3):-
- Division of Neonatology, Department of Pediatric Medicine, Medical College and Hospital Kolkata, Kolkata, West Bengal, India
- Pediatric Intensive Care Unit, Department of Pediatric Medicine, N. R. S. Medical College, Kolkata, West Bengal, India
- Department of Pharmacology, Institute of Post-Graduate Medical Education and Research and Seth Sukhlal Karnani Memorial Hospital, Kolkata, West Bengal, India
- Sick Newborn Care Unit (SNCU), Department of Pediatric Medicine, Medical College Kolkata, Kolkata, West Bengal, India
- Department of Pediatric Medicine, R. G. Kar Medical College, Kolkata, West Bengal, India
Tapas Kumar Sabui, Department of Pediatric Medicine, R. G. Kar Medical College, Kolkata, West Bengal, India, [email protected]
Manuscript Received: August 15, 2021
Manuscript Accepted: September 17, 2021
Earlyview Date: September 17, 2021
Conflicts of Interest
No conflicts declared.
There is no established diagnostic test available to diagnose neonatal sepsis. Tumor necrosis factor α (TNFα), interleukin 1β (IL1β) and interleukin 6 (IL6) showed some promising result in some recent study in this respect, but their role in diagnosis and prognosis of neonatal sepsis is not yet conclusive. In this study we have tried to identify diagnostic and prognostic ability of these biomarkers in neonatal sepsis.
In this cross sectional study blood sample for 3 cytokines were collected at diagnosis of neonatal sepsis fulfilling diagnostic criteria by purposive sampling and values were compared with normal healthy newborns. Each of the cytokines was evaluated separately to identify, whether they can detect neonatal sepsis with at least 70% sensitivity and specificity. At the same time their prognostic value was also evaluated in terms of disease severity and mortality.
Among twenty normal newborn mean (SD) values of TNFα, IL1β and IL6 was 39.7 (21.5)pg/ml, 34.6 (20.9) pg/ml and 44.4 (33.0) pg/ml respectively. While in sepsis group (n=40) the same were 69.6(26.0) pg/ml, 57.7 (29.0) pg/ml and 204.6 (169.2) pg/ml respectively. All these differences were statistically significant (p<0.05). IL6 was able to diagnose neonatal sepsis with 80% (95%CI 64.4 to 90.9) sensitivity and 85% (95% CI 62.1 to 96.8) specificity considering a cut off value of 61.8 pg/ml with area under the curve 0.899. This result was better than other two biomarkers.
IL6 may be considered as a good diagnostic tool for neonatal sepsis. None of the biomarkers were able to prognosticate neonatal sepsis.
İnterleukin 1 beta (IL1β), interleukin 6 (IL6), tumor necrosis factor alpha (TNFα), neonatal sepsis, sepsis prognosis
Neonatal sepsis globally is a major cause of mortality and morbidity.South Asia accounts for 3.5 millionneonatal sepsis cases per year. Sepsis is the second most common cause of neonatal mortality in India.
The major problem with neonatal sepsis is that it presents with many subtle and nonspecific symptoms. High index of suspicion is necessary to diagnose sepsis early.Severity of illness also varies remarkably among cases. Some of these neonates progress rapidly to severe sepsis and septic shock if not treated early. On the other hand there is significant concern about unnecessary antibiotic use. Frequent use of antibiotics in neonatal intensive care unit (NICU) is a common practice. Multiple and higher generation antibiotics are often usedwithoutdefinite evidence of sepsisand there is emergence of multi drug resistant organism.[5,6]
This problem is possibly aggravated by the fact that there is no singlegood test available to diagnose and assess severity of sepsis.Blood culture, which is regarded as the gold standard for diagnosis of neonatal sepsis , is time consuming, takes at least 48 to 72 hoursand provides a variable yield (8-73%).[7,8,9]
Different biomarkers, like C reactive protein, procalcitonin, serum amyloid A, lipopolysaccharide-binding protein, protein biomarkers, cytokines and chemokines, cell-surface antigens have been evaluated for their role in diagnosis of neonatal sepsis.Tumor necrosis factor α (TNFα), interleukin 1β (IL1β), interleukin 6 (IL6) have shown some promises in this respect in recent studies, but their role is not yet conclusive.[11, 12, 13, 14] Prognostic value of these biomarkers has been evaluated in very few studies.[15, 16] There is also huge variation of study results in different geographical region.[11,12]Studies from India are limited.[15, 17, 18] In our study we have tried to evaluatethe role of TNFα, IL1β and IL6 in diagnosis of neonatal sepsis and assess if they can predict sepsis severity and mortality.
This cross sectional study among term appropriate for gestational age newborns was performed in Sick Newborn Care Unit (SNCU) of a tertiary care teaching Hospital in Eastern India from December 2017 to November 2018. Institutional ethics approval was obtained and informed consent was taken from parents of study subjects.
As there is no valid definition for neonatal sepsis, it was diagnosed based on history, certain risk factors, clinical features and positive sepsis screen result by two independent senior doctors. Relevant history includedfailure to suck, lethargy, inconsolable cry, abnormal movement,abnormal skin color. Risk factor for early onset sepsis recorded were low birth weight (<2500 g) or prematurity, febrile illness in the mother with evidence of bacterial infection within 2 weeks prior to delivery, foul smelling and/or meconium stained liquor,rupture of membranes for over 24 hours, single unclean or more than 3 sterile vaginal examination(s) during labor, prolonged labor (sum of 1st and 2nd stage of labor > 24 hours),perinatal asphyxia. Clinicalsigns of sepsis included the following: apnea, tachypnea(>60/min), nasal flaring, retraction, cyanosis, bradycardia (<100/min), tachycardia (>180/min), abdominal distention, hypotonia, seizures, prolong capillary refilling time(over 2 seconds). The various components of the septic screen were total leukocyte count (< 5000/mm3), absolute neutrophil count (low counts as per Manroe chart , immature to total neutrophil ratio(>0.2), micro-erythrocyte sedimentation rate (>15 mm in 1st hour) and C reactive protein (>1 mg/dl). If 2 or more parameters of the sepsis screen were positive then it was considered positive.[7,8,21]Sepsis was diagnosed in presence of any of these clinical features along with positive sepsis screen result. Neonate with more than two risk factors for early onset sepsis with positive sepsis screen was also considered as neonatal sepsis even if asymptomatic.
Term appropriate for gestational age neonates with a diagnosis of sepsis were recruited in the study by purposive sampling. Neonate with congenital malformations, congenital infections associated with theTORCH complex, suspected immunodeficiency were excluded from the study. No preterm or small for gestational age newborn were included in the study. Consecutively all neonate fulfilling these criterion during study period were included in sepsis group. Blood sample for cytokines were also collected from term appropriate for gestational age healthy newborns (controls) from same unit of same hospital during routine blood sampling for neonatal screening of congenital diseases after obtaining informed consent.
Whole blood sample for culture sensitivity and cytokine (TNF-α, IL-1β, IL-10)levels were collected immediately after inclusion in the study and before starting antibiotics. Blood culture wascarried out by an automated system (BacT/Alert3D, Biomeriux). Blood sample for cytokines were centrifuged at 2500 rpm for 15 minutes. Separated serum was stored at –80◦c. The levels of TNF-α, IL1β, and IL6 were estimated by ELISA as per manufacturer’s instruction (Raybiotech Inc. Georgia, USA). Each cytokines level was measured at 450 nm by ELISA reader (Tecan, Switzarland). Required serum sample for each cytokines were 100 µL. Minimum detectable range was 30 pg/ml (30-6000 pg/ml) for TNFα, 0.3 pg/ml (0.3-100pg/ml) for IL1β, and 3 pg/ml (3-1000pg/ml) for IL6.
Newborns were classified as proven sepsis (blood culture positive),suspected sepsis (blood culture-negative) and control (healthy newborns). Sepsis severity was assessed by SNAP II score at the time of diagnosis. A score of ≥40 was considered as severe sepsis. All these babies were prospectively followed up for ultimate outcome: cured/mortality.
Data have been summarized by routine descriptive statistics, namely mean and standard deviation for numerical variables that were normally distributed. Numerical variables were compared between groups by one way analysis of variance (ANOVA), followed by an appropriate post hoc test. Fisher’s exact test or Pearson’s Chi-square test was employed for intergroup comparison of categorical variables. SPSSStatistics version 17 [Illinois, Chicago: SPSS Inc., 2008] was used for analysis.
We also attempted receiver operating characteristic (ROC) curve analysis, to see whether any of the three biomarkers (TNFα, IL-1β and IL-6) can predicts the occurrence of sepsis with at least 70% sensitivity and specificity. Differences in levels of these biomarkers with respect to disease severity and in survived and mortality group were also assessed.
Among 40 patients with suspected sepsis 20 were culture positive (proven sepsis) and rest 20were culture negative (suspected sepsis). Twenty normal babies were recruited as control.About (n=21/40)50% patient had early onset sepsis. Mean (SD) birth weight was 2863.5 ± 464.0 g, 2632.2 ±304.3 g and 2607.0 ±271.1 g in normal, suspected sepsis and proven sepsis group respectively. Gestational age in these groups was 38.30 ± 1.4 weeks, 38.1 ± 1.0 weeks and 37.8 ± 1.0 weeks respectively. There was no statistically significant difference between groups. Their baseline characteristics are shown in Table I.
The organisms identified among 20 culture positive patients were Klebsiella (9), acinetobacter (3) E. coli (2), Pseudomonas (2), Enterococcus (2), Staphylococcus aurius (2). Mean ± standard deviation (SD) values of leukocyte count,absolute neutrophil count, immature to total neutrophil ratio, erythrocyte sedimentation rate and C-reactive protein levels in sepsis group was 10668.8 ± 7224.9 /mm3, 6007.6 ± 5397.9 /mm3, 0.24 ± 0.16, 13.0 ± 5.8 mm in first hour, 2.2 ± 1.7 mg/dl respectively.
Values of TNFα, IL1β and IL6 in different groups were illustrated in table II. Irrespective of blood culture report there was statistically significant difference in the levels of all3 cytokines between sepsis group and normal newborn (p <0.05). However,there was no statistically significant difference of plasma cytokine levels between suspected and proven sepsis group (p >0.05).
Utility of each of the biomarkers to diagnose sepsis (both suspected and proven) assessed by ROC analysis showed area under the curve (AUC) to be 0.814,0.740 and 0.899, respectively for TNFα, IL1β and IL6.Criterion value assessed from ROC curve were >36.8 pg/ml for TNFα (sensitivity 95%, specificity 55%), >56.5 pg/ml (sensitivity 50%, specificity 95%) for IL1β and >61.8 pg/ml (sensitivity 80%, specificity 85%) for IL6.Thus only IL6 offered satisfactory sensitivity and specificity towards diagnosing sepsis in the newborn (Table III), (figure 1).
There were no statistically significant differences in any of the biomarkers level between severe sepsis and non severe sepsis group. There were also no statistically significant findings in relation to any of the three biomarkers with respect to mortality prediction. (Table IV)
In our study we found that value of all 3 biomarkers namelyTNFα, IL1β and IL6, were significantly high in neonate with sepsis as compared to healthy ones. IL6 was found to have diagnostic ability for neonatal sepsis with reasonable sensitivity and specificity. However, none of the biomarkers were able to prognosticate sepsis severity in terms of treatment support and mortality.
Studies from different part of the world have shown some important role of these biomarkers in diagnosis of neonatal sepsis, but there is non-uniformity in sensitivity, specificity and cut off value between studies. In a recent meta-analysis on TNFα as a diagnostic marker of neonatal sepsis by Bokun LV et al., has reported that studies done in Northern hemispheres had a pooled sensitivity of 84.0% and specificity was 83.3% while that for Southern hemisphere was 68.0% and 88.5% respectively for diagnosis of late onset neonatal sepsis. For diagnosis of early onset sepsis pooled sensitivity was 66.1% and specificity 75.6%.In our study we have found TNFα had 95% sensitivity and 55% specificity to diagnose neonatal sepsis irrespective of type of sepsis.
Atici A et al. in their study found that IL1β level diminishes in neonatal sepsis while in other studies it was elevated.[14, 24]IL1β was found to have a sensitivity of 27% and specificity of 70% to diagnose neonatal sepsis in the study by Ayazi et al. On the other hand We found that IL1β levels increased in neonatal sepsis with sensitivity of 50% and specificity of 95%.
IL6 has been the most extensively studied interleukin till date. It has sensitivity of 71–100% and specificity of 47-95% to diagnose neonatal sepsis in different studies with different cut off values (10–100 pg/ml).IL6 has a very short half-life and hence, shows decline in sensitivity within24-48 hours.34Some studies that have explored both TNFα and IL6 showed that ,as a single biomarker diagnostic tool, TNFα was better than IL6.[17, 27] TNFα has showed 60% sensitivity and 100% specificity, in combination with IL6 levels, for the diagnosis of sepsis in study by Debont ESJM et al. In our study, we found a good sensitivity for TNFα but with a low specificity, while IL1β had a good specificity but with poor sensitivity. IL6 was found to have reasonable sensitivity (80%) and specificity (86%) with maximum AUC (0.899). So it may be considered as best single biomarker among the three for diagnosis of neonatal sepsis.
There are few studies that have highlighted the prognostic relation of elevations of these biomarkers and severity of sepsis. Girardin et al.had shown that serum TNFα levels may have a direct correlation with the severity of sepsis and the mortality rate during the development of sepsis in newborns at risk for infections. Studies on adults with sepsis have shown increasing IL6 level to be associated with higher mortality rates.Even after extensive search of published literature no data on prognostic value of IL1β could be found. However our analysis of newborns with sepsis did not reveal any relation of elevated biomarker levels with severity of sepsis.
Previous studies have demonstrated difference in level of biomarkers in acute and post-acute phase, and also with treatment.[14,30]However, ours being a cross sectional study serial measurements were not taken, and therefore changes in the level of biomarkers with course of disease were not identified. Although prematurity and small for gestational age (SGA) are known risk factor for neonatal sepsis, they were not included in the study, for the possibility of variation in biomarkers level in them. As this study was done only among term AGA baby, role of these biomarkers among preterm and small for gestational age newborn are not determined. Further study in these groups of neonate is warranted, as they are the more vulnerable population.
Although TNFα, IL1β and IL6 were not able to prognosticate neonatal sepsis, they had a good role in diagnosis of neonatal sepsis among term appropriate for gestational age neonate. All these biomarkers were significantly elevated in neonatal sepsis and IL6 may have diagnostic utility with reasonable sensitivity (80%) and specificity (85%).
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Bar Diagram Showing Mean Difference in Biomarkers between Normal Newborn and Newborn with sepsis
ROC Curve of Three Cytokines with Reference Line
Baseline Characteristics of Three Groups
:Comparison of Biomarker Levels between Three Study Groups
Receiver operating characteristic curve (ROC) curve analysis to show performance of three biomarkers in diagnosing neonatal sepsis
Values of Biomarkers in Different Outcome Group