Indian Journal of Pathology and Microbiology

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 61  |  Issue : 1  |  Page : 81--84

Evaluation of procalcitonin as a diagnostic marker in neonatal sepsis


Marie Victor Pravin Charles1, Ramakrishnan Kalaivani1, Soma Venkatesh2, Arunava Kali1, Kunigal Srinivasiah Seetha1,  
1 Department of Medical Microbiology, Mahatma Gandhi Medical College and Research Institute, Puducherry, India
2 Department of Pediatrics, Mahatma Gandhi Medical College and Research Institute, Puducherry, India

Correspondence Address:
Marie Victor Pravin Charles
Mahatma Gandhi Medical College and Research Institute, Cuddalore Main Road, Pillaiyarkupam, Puducherry - 607 403
India

Abstract

Context: Neonatal sepsis is an early infection occurring within 28 days of the postnatal life. It has nonspecific signs and symptoms which make the diagnosis cumbersome. It inflicts an increase in morbidity and mortality among neonates. Procalcitonin (PCT) is yet another acute phase reactant, which is synthesized by the C-cells of thyroid gland. Aims: The aim of our study is to evaluate PCT as a diagnostic marker of neonatal sepsis in comparison with C-reactive protein (CRP). Subjects and Methods: A prospective cross-sectional study was conducted at our tertiary care hospital in Puducherry. The study was conducted over a period of 5 months from November 2015 to 2016. The study included all neonates with clinical signs of sepsis. The neonates were assigned into three groups as proven sepsis, suspected sepsis, and no sepsis group. The CRP level and PCT level were compared between the three groups, and their sensitivity and specificity were calculated. Statistical Analysis Used: The mean, standard deviation, and standard error of mean were calculated. The groups were compared using one-way ANOVA. The diagnostic test efficiency was evaluated by receiver operating characteristic curve analysis. Results: A total of 75 neonates were included in our study. There were 9 (12%) neonates with proven clinical sepsis, 47 (62.6%) neonates with suspected clinical sepsis, and 19 (25.3%) neonates with no sepsis. The mean and standard error of mean were calculated for CRP and PCT in all the three groups. The results showed a sensitivity of 88.90% for both CRP and PCT and specificity of 89.40% for CRP and 80.30% for PCT. The common organisms isolated from culture-positive group were Escherichia coli (22.2%), Pseudomonas aeruginosa (22.2%), and Candida albicans (22.2%), followed by Klebsiella pneumoniae, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus. Conclusions: PCT may not be sufficiently used as a sole marker of sepsis in neonates compared to CRP. PCT in conjunction with CRP and other tests for septic screen can aid in better diagnosis of neonatal sepsis.



How to cite this article:
Pravin Charles MV, Kalaivani R, Venkatesh S, Kali A, Seetha KS. Evaluation of procalcitonin as a diagnostic marker in neonatal sepsis.Indian J Pathol Microbiol 2018;61:81-84


How to cite this URL:
Pravin Charles MV, Kalaivani R, Venkatesh S, Kali A, Seetha KS. Evaluation of procalcitonin as a diagnostic marker in neonatal sepsis. Indian J Pathol Microbiol [serial online] 2018 [cited 2020 Aug 14 ];61:81-84
Available from: http://www.ijpmonline.org/text.asp?2018/61/1/81/228198


Full Text



 Introduction



Neonatal sepsis is an early infection occurring within 28 days of the postnatal life. Neonatal sepsis is divided into two types as early-onset sepsis which occurs within 3 days of birth and late-onset sepsis which occurs later.[1] It inflicts an increase in morbidity and mortality among neonates.[2] The estimated global neonatal death rates indicate 40% mortality due to sepsis. Further lack of accurate assessment and limited medical resources hamper accurate detection of neonatal sepsis among the developing countries.[3] Remarkably, it has nonspecific signs and symptoms which make the diagnosis cumbersome. It includes fever or hypothermia, cyanosis and apnea, lethargy or irritability, feeding difficulties, hypotonia, seizures, bulging fontanel, poor perfusion, bleeding problems, abdominal distention, and hepatomegaly. Even though blood culture is warranted as a gold standard method in identifying sepsis, the sensitivity varies based on the volume of blood and the bacterial load.[4] Total leukocyte count, absolute neutrophil count, immature-to-total neutrophil ratio, and C-reactive protein (CRP) are other parameters used to identify sepsis. Procalcitonin (PCT) is yet another acute phase reactant which is synthesized by the C-cells of thyroid gland. It is a peptide composed of 116 amino acids and a glycoprotein. It is also produced by hepatocytes and macrophages when there is an encounter by bacterial toxins.[5] Its utility as a marker in severe bacterial infection was first reported in 1993.[6] PCT elevation is minimal in meconium aspiration, hypoxemia, and trauma on the contrary to CRP, which would be a better marker to identify neonatal sepsis.[7] The aim of our study is to evaluate PCT as a diagnostic marker of neonatal sepsis in comparison with CRP.

 Subjects and Methods



Study design

A prospective cross-sectional study was conducted at our tertiary care hospital in Puducherry. The study was conducted over a period of 5 months from November 2015 to March 2016. The study included all neonates with clinical signs of sepsis such as fever or hypothermia, cyanosis and apnea, lethargy or irritability, feeding difficulties, hypotonia, grunting, seizures, bulging fontanel, poor perfusion, bleeding problems, abdominal distention, and hepatomegaly. The neonates were assigned into three groups as proven sepsis, suspected sepsis, and no sepsis group. The proven sepsis group included those neonates with both clinical signs and blood culture positivity. The clinically suspected sepsis group included those with clinical signs positive but culture negative. The no sepsis group was both culture and clinical signs negative. All neonates with positive blood culture were treated with appropriate antibiotic therapy at our Neonatal Intensive Care Unit. The CRP level and PCT level were compared among the three groups, and their sensitivity and specificity were calculated. This study was submitted at the institutional human ethics committee and approval was obtained. Informed consent was obtained from both parents for all the neonates who were involved in the study.

Sample collection

Blood was collected from the neonates with clinical signs of sepsis. The blood samples were taken before the administration of antibiotics. About 1–2 ml of the blood was collected from the peripheral vein using a 22-gauge syringe in BACTEC Peds Plus/F culture vial (Becton and Dickinson company, USA), and another 2 ml of blood was taken in separate vial for serological test.

The culture vials were placed in BACTEC FX automated blood culture system. The culture vials were removed on positive indication from the BACTEC machine. The positive blood culture samples were subcultured in to blood agar, MacConkey agar, and chocolate agar. The plates were incubated at 37°C for 24–48 h. On identification of growth, the bacteria were identified and antibiotic susceptibility tests were carried out by standard bacteriological procedures. Culture-negative bottles were removed from the machine at the end of 5 days.

C-reactive protein latex agglutination test

The blood samples collected in separate vials were allowed to clot. The serum was centrifuged and separated. CRP was done on the serum samples using commercial latex agglutination kit (Agappe Diagnostics Ltd., Mumbai, India). A semi-quantitative test was carried out to identify the titer in positive cases. The sample was tested in dilutions of ½, 1/4, 1/8, 1/16, and 1/32. The CRP concentration was obtained by the formula: CRP concentration = sensitivity × titer, where the sensitivity is 0.6 mg/dl.

Procalcitonin

It was performed using Raybio human PCT ELISA kit. All reagents, samples, and standards were prepared as instructed. Hundred microliters of standard or sample was added to each well and incubated 2.5 hours at room temperature. Hundred microliters prepared biotin antibody to each well and incubated 1 hour at room temperature. Hundred microliters of prepared streptavidin solution was added and incubated 45 min at room temperature. Hundred microliters TMB one-step substrate reagent was added to each well and incubated 30 min at room temperature. Fifty microliters stop solution was added to each well. Results were read at 450 nm immediately. The concentration of PCT was calculated as per the kit instructions.

Statistical analysis

The statistical analysis was done using SPSS for Windows, Version SPSS 16.0 (SPSS Inc., Chicago, IL, USA). The mean, standard deviation, and standard error of mean were calculated. The groups were compared using one-way ANOVA. The diagnostic test efficiency was evaluated by receiver operating characteristic (ROC) curve analysis. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

 Results



A total of 75 neonates were included in our study. There were 9 (12%) neonates with proven clinical sepsis, 47 (62.6%) neonates with suspected clinical sepsis, and 19 (25.3%) neonates with no sepsis. The mean and standard error of mean were calculated for CRP and PCT between all the three groups as shown in [Table 1]. P value was statistically significant (P< 0.05) in both CRP and PCT. The sensitivity, specificity, PPV, and NPV of the two diagnostic tests were calculated. ROC curve was elaborated for both CRP and PCT at 95% confidence interval. The cutoff levels with optimum diagnostic efficiency derived from the curve for CRP was >0.3 mg/dl and PCT was >1.32 ng/ml. This yielded a sensitivity of 88.90% for both CRP and PCT and specificity of 89.40% for CRP and 80.30% for PCT [Table 2].{Table 1}{Table 2}

The common organisms isolated from culture-positive group were Escherichia coli (22.2%), Pseudomonas aeruginosa (22.2%), and Candida albicans (22.2%) followed by Klebsiella pneumoniae, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus as shown in [Table 3].{Table 3}

 Discussion



Sepsis includes a cascade of inflammatory process whose diagnosis is complicated due to the nonspecific signs and symptoms. It is a challenging task to establish an ideal diagnostic marker of sepsis as most of these makers rise in any kind of noninfective inflammatory process. Acute phase reactants, cell surface markers, granulocyte-colony-stimulating factor, and cytokines have been proposed as an early marker of sepsis in a neonate. CRP is an acute phase reactant which rises following any tissue damage or infective process. It rises 6–8 h following any exposure with a half-life of 19 h,[8] whereas PCT is produced by monocytes and hepatocytes which rise in 4 h with a half-life of 25–30 h.[5] Comparatively, CRP rises late following any inflammation. There are several studies showing controversies on an ideal marker of sepsis. The aim of our study is to evaluate PCT as a diagnostic marker of neonatal sepsis in comparison with CRP. PCT has been widely evaluated by researchers across the world. A multicenter study conducted in Spain revealed that PCT was not reliable and sufficient as a sole marker for sepsis.[9] On the contrary, Auriti et al. reported an increased diagnostic accuracy of PCT in neonates.[10] A study on perinatal influence on PCT showed that antibiotic therapy was associated with false-negative PCT results.[11] In our study, we found that both CRP and PCT were statistically significant in comparison between all the three groups. The sensitivity of both CRP and PCT was 88.90% each. The specificity for CRP was 89.40% and that of PCT was 80.30%. Park et al. reported that PCT had a sensitivity of 88.79% and specificity of 58.17%, while CRP had a sensitivity of 100% and specificity of 52.66%.[12] Other similar studies showed that PCT had a sensitivity of 66%–92% and specificity of 50%–97%.[13],[14],[15] In our study, the sensitivity was similar for both CRP and PCT whereas the specificity was lesser in PCT compared to CRP. This denotes that PCT as a separate diagnostic tool for neonatal sepsis can lead to more false-positive cases. The main problem with PCT is the physiological increase during the first 48 h of life which returns to normal on the 4th day.[16] Further studies have shown that premature birth is associated with rise in PCT without any bacterial infection.[17]

 Conclusions



PCT may not be sufficiently used as a sole marker of sepsis in neonates compared to CRP. PCT in conjunction with CRP and other tests for septic screen can aid in better diagnosis of neonatal sepsis in the scenarios where this burden is high and other assays such as interleukin are expensive.

Financial support and sponsorship

The study was financially supported by Sri Balaji Vidyapeeth University.

Conflicts of interest

There are no conflicts of interest.

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