|Year : 2017 | Volume
| Issue : 3 | Page : 105-109
Utility of volume, conductivity and scatter parameters for early diagnosis of neonatal sepsis
Anjali Kelkar, Preeti Doshi, Tushar Tyagi, Amit Nisal, NS Mani
Department of Pathology, Bharati Vidyapeeth University Medical College, Pune, Maharashtra, India
|Date of Web Publication||18-Sep-2017|
Department of Pathology, Bharati Vidyapeeth University Medical College, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: Neonatal sepsis comprises a major problem in India. Early detection of neonatal sepsis is challenging as clinical signs are subjective and the gold standard, a positive culture, requires 1–3 days. Volume conductivity scatter (VCS) data were obtained simultaneously with the differential count without additional cost or sample requirement. The present study was undertaken in a tertiary care teaching hospital with the aim of evaluating VCS data and other laboratory parameters for diagnosis of neonatal sepsis.
Materials And Methods: Peripheral blood samples of 500 consecutive neonates were analyzed over a period of 2 years for complete blood count (CBC) with band cells, eosinophils, C-reactive protein (CRP), and culture. VCS parameters were obtained simultaneously from Beckman coulter analyzers for neonates aged 0–28 days with suspected sepsis.
Controls: Gestation-matched healthy controls with no clinical or laboratory suspicion of infection. The study population was divided into following groups: proven sepsis, clinical sepsis, and no sepsis. A cutoff value of 0.3615 based on CRP, mean neutrophil volume (MNV), and volume distribution width (VDW) was taken to indicate the presence or absence of sepsis; based on the previously published work by Celik et al.
Results: A total of 500 consecutive samples of neonates admitted in neonatal Intensive Care Unit of Bharati Hospital were analyzed. All the three groups were analyzedd with respect to CBC values, peripheral blood smear, VCS parameters, CRP values and blood cultures which gave a sensitivity of 76%, specificity of 88%, positive predictive value 77%, and negative predictive value 87%.
Conclusions: We analyzed the utility of VCS parameters along with CRP for early diagnosis of neonatal sepsis. The study results indicate that the factor based on MNV, VDW, and CRP with cutoff of 0.3615 is a useful indicator of neonatal sepsis without incurring additional cost, with high specificity (88%), and high negative predictive value (87%).
Keywords: Early diagnosis, neonatal sepsis, volume conductivity scatter
|How to cite this article:|
Kelkar A, Doshi P, Tyagi T, Nisal A, Mani N S. Utility of volume, conductivity and scatter parameters for early diagnosis of neonatal sepsis. J Appl Hematol 2017;8:105-9
|How to cite this URL:|
Kelkar A, Doshi P, Tyagi T, Nisal A, Mani N S. Utility of volume, conductivity and scatter parameters for early diagnosis of neonatal sepsis. J Appl Hematol [serial online] 2017 [cited 2018 Jul 22];8:105-9. Available from: http://www.jahjournal.org/text.asp?2017/8/3/105/214996
| Introduction|| |
According to the World Health Organization estimate, there are about 5 million neonatal deaths per year, 98% occurring in developing countries. The neonatal mortality rate varies from 1–4/1000 live births in developed countries to 10–50/1000 live births in developing countries., Sepsis is the most common cause of mortality, responsible for 30%–50% of total neonatal deaths in developing countries., It is estimated that up to 20% of neonates develop sepsis and approximately 1% die of sepsis related causes.
“Neonatal sepsis” or “sepsis neonatorum” refers to generalized bacterial infection of infants during the 1st month of life. It also encompasses various systemic infections of the newborn; such as septicemia, pneumonia, meningitis, arthritis, osteomyelitis, and urinary tract infections. Superficial infections such as conjunctivitis and oral thrush are not included in it.,
The early signs of neonatal sepsis may be subtle and different at different gestational ages. Hence, the diagnosis is often delayed or missed until the process has become widespread.
Neonatal sepsis can be classified into two categories depending on the onset of symptoms.
- Early-onset neonatal sepsis: It presents within the first 72 h of life. Organisms prevalent in the maternal genital tract cause these infections
- Late-onset neonatal sepsis: It presents after 72 h of age. Organisms thriving in the external environment of the home or the hospital cause these infections.
The multiple hematological and biochemical changes in the blood of neonates during sepsis are as follows- leukocytosis in the form of neutrophilia followed by leukopenia with neutropenia, with the presence of immature neutrophils in the circulation, various morphological changes in neutrophils such as toxic granulation, cytoplasmic vacuolation and Dohle bodies, thrombocytopenia, changes in plasma proteins such as increase in levels of C-reactive protein (CRP), fibrinogen, haptoglobin, and ceruloplasmin and decrease in levels of prealbumin and transferrin.
The outcome of a neonate with sepsis largely depends on its early identification. To meet this requirement, several rapid diagnostic tests have been described recently. Individually, these tests had low sensitivity and specificity; therefore, a combination of these tests was also studied by many workers to formulate a reliable sepsis algorithm.,
Automated hematology analyzers yield several electronic and optical leukocyte indices such as volumes of leukocyte subsets, cellular electrical conductivity, etc. optical light scatter. These have shown promise in the early and sensitive diagnosis of diseases characterized by leukocyte abnormalities. The leukocyte differential in Beckman coulter analyzers (Beckman Coulter, Miami FL USA) is based on volume conductivity scatter (VCS) technology (volume, conductivity, and scatter) that quantifies leukocyte cell volume by voltage impedance (V), cytoplasmic and nuclear density by radio frequency conductivity (C), and cytoplasmic granularity and nuclear complexity by laser light scatter(S).
“Mean neutrophil volume (MNV) + CRP” criterion is documented as a potentially useful tool for the evaluation of neonates with proven as well as suspected sepsis. Its use along with other VCS parameters could improve timely recognition of serious infections in this vulnerable population. VCS data are obtained simultaneously with the differential count without any requirement of additional testing, extra sample, reagents, time, or expenditure. These tests are simple, rapid, requiring less expertise, and are economical. These can be carried out even in remote areas in developing countries where culture facilities may be absent.
Hence, this study proposes to use these early markers, i.e., total leukocyte count, immature cell to total neutrophil ratio, presence of toxic granules and cytoplasmic vacuolation in neutrophils, platelet count, CRP, and VCS technology of Coulter LH 750 hematology analyzer in the early diagnosis of neonatal sepsis, which in turn will help to reduce the neonatal morbidity and mortality.
| Materials and Methods|| |
This is a prospective study, conducted in the affiliated teaching hospital and Department of Pathology of a Medical college from August 2014 to July 2016. A total of 500 consecutive neonates of both sexes, referred to neonatology unit with clinical suspicion of sepsis in indoor as well as out-patient department. Approval from the Institutional Ethical Committee was obtained. Informed written consent was obtained from the parent/guardian. Under all strict aseptic precautions and before any antibacterial therapy, an intravenous scalp vein was inserted into a peripheral vein. With a 2.0 ml syringe, 0.5–1 ml blood (0.5 ml in babies with weight <1000 g and 1 ml in babies with weight >1000 g) was drawn.
Investigations were carried out as mentioned below:
- Blood/cerebrospinal fluid (CSF)/urine culture and sensitivity
- Complete blood count (CBC)
Various cutoffs were obtained using receiver operating characteristic (ROC) curves. The cutoffs and models described in the literature using effective modeling of molecular activity (EMMA) statistical program have also been evaluated for their applicability and utility as reported by Celik et al.,
Model 1 – Sepsis = −1.17 + 0.015 × (CRP) + 0.009 × (MNV).
Model 2 – Sepsis = −1.35 + 0.0136 × (CRP) + 0.0074 × (MNV) + 0.0123 × volume distribution width (VDW).
| Results|| |
Out of the total 500 cases of suspected sepsis, the prevalence of blood culture proven sepsis was 22% [Table 1].
Most common organisms isolated were Klebshiella Pneumonia (32.7%) followed by Escherichia coli (21.8%), Enterococcus spp. (11.8%), methicillin-resistant Staphylococcus aureus (10.9%), Acinetobacter baumanni (10%), and S. aureus (10%) [Table 2]. Other organisms isolated were CONS group (12%), Pseudomonas (4.5%), Enterobacter (2.7%), Burkholderia cepacia (1.8%), ESBL K. pneumonia (1.8%), Aerococcus viridans (0.9%), Citrobacter (0.9%), and Proteus mirabilis (0.9%).
Out of the total 110 cases of culture proven sepsis, early-onset sepsis was seen in 61.3%, whereas late-onset sepsis was seen in 38.7% of cases [Table 3].
Cases of sepsis had significantly lower birth weight as compared to controls with half of the cases had a birth weight of <1.5 kg compared to 12.6% controls (P< 0.05) [Table 4].
ROC curve analysis was performed to determine the cut-off point for MNV, CRP, white blood cells, and EMMA I and II formulas to predict culture positivity. The area under the curve was significant for all of these variables (0.773, 0.922, 0.614, 0.908, and 0.895). It was observed that taking the cutoff of MNV as 143.5 gave a sensitivity of 90% and specificity of 43% while the cutoff of white blood cell count of 14 × 109/L gave a sensitivity of 63.6% and specificity of 52.5% and that of CRP level of 2 gave a sensitivity of 94.5% and specificity of 71.4% [Table 5].
EMMA I and II at cutoff of 0.357 and 0.290 give the sensitivity of 83.65 and 80% and specificity of 87% and 83.6% [Table 6].
ROC curve analysis also showed that the MNV and EMMA I and II formulae had larger area under curve when compared with total leukocyte counts suggesting their superior diagnostic value for cases of sepsis.
| Discussion|| |
Neonatal sepsis is a serious illness with high morbidity and mortality. Although it is a life-threatening condition, it can be treated if an early diagnosis is made. The gold standard for diagnosis of sepsis is isolation of bacteria from blood culture, which take at least 48 h. Thus, realizing the importance of early and correct diagnosis of neonatal sepsis, many workers have made an attempt to diagnose sepsis by means of simple laboratory tests, which are direct, or indirect, early markers of infection. Celik et al., in the largest published study so far, suggested that neutrophil VCS parameters and their distribution widths are useful both for early diagnosis and evaluation of treatment efficacy in neonatal sepsis without requirement for any extra blood collection. They observed significant increases in MNV, VDW, conductivity distribution width (CDW), and significant decreases in MNC and MNS in septic newborns. There were significant decreases in MNV, VDW, and CDW, whereas MNC and MNS increased at the end of the treatment.
This study was conducted in a tertiary care teaching hospital in Western India. The institute has a busy neonatology unit. The laboratory provides 24 × 7 services with trained faculty and automated cell analyzers from Beckman Coulter (LH 750) providing the V (Volume), C (Conductivity) and S (Scatter) parameters for the CBC samples.
In this study, the age range for the patients was between 0 and 30 days and maximum number of cases 73 were between 0 and 3 days for early-onset of sepsis and age range for late onset of sepsis 37 were between 4 and 30 days [Table 7].
Microbiological culture and sensitivity study (blood/CSF/urine) was performed in all 500 cases of suspected sepsis 110 were bacteriologically positive. In this study, most common organism isolated was K. pneumoniae (32.7) followed by E. coli (21.8%), Enterococcus spp. (11.8%).
Similar observations were also noted by Sharma (2013), Pjyothi (2013), and Muley (2015). Thakur (2016) observed that K. pnemoniae to be most common causative organism.
In the present study [Table 8], Model I with the cutoff of >0.35 gave a sensitivity of 83.60% and specificity of 87% and Model II with the cutoff of >0.270 gave a sensitivity of 80.00% and specificity of 83.60% as compared to Celik et al. where they had a slightly higher sensitivity and specificity. The combination of different sepsis marker like interleukin, procalcitonin could lead to increase in sensitivity and specificity in our study; although, additional cost factor will have to be considered.
|Table 8: Comparing effective modeling of molecular activity cut off in the present study with the previous study|
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| Conclusions|| |
In this study, 500 consecutive cases were studied for prevalence of neonatal sepsis and to evaluate the performance of existing laboratory parameters of early diagnosis of neonatal sepsis. The neutrophil VCS parameters were found to be very useful for early diagnosis of neonatal sepsis without requirement for any extra blood collection. It is simple, easy, nontime-consuming, and at no additional cost.
Early-onset sepsis was more prevalent in our setting and neonates with low birth weight were significantly more affected than the normal birth weight ones. K. pneumoniae was the most common organism.
MNV at a cutoff 143.5 gave a sensitivity of 90% and specificity of 43% and with a cutoff of 150 gave a sensitivity of 69.1% and specificity of 69.8%.
In our setting, we could apply the EMMA diagnostic models I and II, described by Celik et al., which combined VCS parameters with CRP. For Model I, we demonstrate the sensitivity of 83.6% and specificity of 87% at the cutoff of 0.357. For Model II, our sensitivity was 80% and specificity of 83.6% at the cutoff of 0.270.
Our data, to the best of our knowledge could be the largest study of VCS parameters for early diagnosis of neonatal sepsis. We find neutrophil VCS parameters useful for this purpose without incurring additional cost and requirement of blood sample.
Analysis of data on follow up of individual neonates was not designed as part of this study.
TT was responsible for collection and analysis of data, PD supervised the data analysis and prepared the first draft of manuscript, AK was responsible for designing the study, critical review, final manuscript preparation, and correspondence. Neonatal ICU, Bharati Hospital, provided the clinical details for all the cases.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8]