|Year : 2018 | Volume
| Issue : 2 | Page : 236-260
|Rapid detection of respiratory syncytial virus in community-acquired lower respiratory tract infections in children by chromatographic assay
Surinder Kumar1, Bhanu Mehra1, Gulshan Rai Sethi2, Sanjeev R Saigal1
1 Department of Microbiology, Maulana Azad Medical College, New Delhi, India
2 Department of Paediatrics, Maulana Azad Medical College, New Delhi, India
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|Date of Web Publication||20-Apr-2018|
| Abstract|| |
Respiratory syncytial virus (RSV) is the single most important viral agent causing pediatric lower respiratory tract infections (LRTIs) worldwide. To evaluate the role of RSV in pediatric LRTIs, we studied 85 children <2 years of age hospitalized for community-acquired LRTIs. Nasopharyngeal aspirates were obtained on admission for the detection of RSV antigen by immunochromatographic assay. Demographic, clinical, and radiological findings for RSV antigen were compared. Data analysis was performed by Chi-square test. A relatively higher number of RSV-infected children 32 (60.4%) were below 6 months of age. Clinical and radiological findings in both RSV-positive and RSV-negative groups were comparable. RSV antigen was positive in 53 (62.4%) with immunochromatography. Our study confirms that RSV plays a significant role in community-acquired LRTIs in children.
Keywords: Chromatographic immunoassay, lower respiratory tract infections, respiratory syncytial virus
|How to cite this article:|
Kumar S, Mehra B, Sethi GR, Saigal SR. Rapid detection of respiratory syncytial virus in community-acquired lower respiratory tract infections in children by chromatographic assay. Indian J Pathol Microbiol 2018;61:236-60
|How to cite this URL:|
Kumar S, Mehra B, Sethi GR, Saigal SR. Rapid detection of respiratory syncytial virus in community-acquired lower respiratory tract infections in children by chromatographic assay. Indian J Pathol Microbiol [serial online] 2018 [cited 2020 Apr 9];61:236-60. Available from: http://www.ijpmonline.org/text.asp?2018/61/2/236/230568
| Introduction|| |
Acute lower respiratory tract infections (LRTIs) are the leading cause of childhood mortality and morbidity, particularly in the developing world. Viruses are the most frequent cause of acute respiratory infections and respiratory syncytial virus (RSV) is the main viral agent causing pediatric LRTIs worldwide., Diagnosis is impossible on clinical grounds alone as the presentation is indistinguishable from other respiratory tract infections and epidemics often overlap. The specific diagnosis of RSV infection is based on the detection of virus or viral antigens or virus-specific nucleic acid sequences in respiratory secretions. Rapid detection of RSV is useful in guiding immediate treatment and minimizing antibiotic overuse. The present study was undertaken to evaluate the role of RSV in etiology of acute community-acquired LRTIs in children aged <2 years by employing chromatographic immunoassay to detect RSV antigen in nasopharyngeal aspirates.
| Materials and Methods|| |
This prospective cross-sectional study included 85 children <2 years of age presented with acute LRTIs and admitted to the Department of Pediatrics of a tertiary care health facility in New Delhi, India, from February 2011 to March 2012.
(1) Age <2 years; (2) presence of cough and fever with breathlessness of <30 days duration, and (3) increased respiratory rate, with or without wheeze.
Hospital-acquired pneumonia, i.e., pneumonia that developed 72 h after hospitalization or within 7 days of discharge.
Enrollment and evaluation of patients
Written informed consent was taken from the parents or legal guardians of children in conformation with standard bioethical norms. The study was duly approved by the Institutional Review Board. A detailed history and clinical examination were performed, and routine laboratory investigations and chest radiographs were obtained. Nasopharyngeal aspirates were collected from all cases as early as possible after hospital admission by employing a suction apparatus consisting of a disposable mucus sucker and sterile phosphate-buffered saline (pH 7.3). The samples were transported at 4°C to the laboratory and were immediately evaluated for RSV antigen using the BD Directigen™ EZ RSV (Becton, Dickinson and Company, MD 21152 USA). All the tests were performed as per the manufacturer's instructions in the kit insert. A visible reddish-purple line next to the test “T” and a reddish-purple line next to the control “C” implied that the RSV antigen was detectable in the specimen (positive); no reddish-purple line next to the test “T” implied that RSV antigen was not detectable in the specimen (negative) while the absence of a visible reddish-purple line next to the control “C” indicated that the test was uninterpretable.
Data were recorded on a predesigned pro forma, and responses were coded for entry in a computer. All the entries were doubly checked for any possible keyboard errors. The difference of proportion between qualitative variables was tested using the Chi-square and Fischer's exact test and between quantitative variables using Student's t-test. A P < 0.05 was considered as statistically significant.
| Results|| |
The age of the patients ranged from 1 month to 2 years, with a mean age of 7.83 ± 6.12 months. The mean age of RSV-positive patients was 8.13 ± 6.28 months. The differential presence of RSV in LRTIs across age groups 1–6 months (Group 1), 7–12 months (Group 2), and 13 months to 2 years (Group 3) was statistically insignificant (P = 0.47, P = 0.30, and P = 1.00, respectively) [Table 1]. RSV positivity was 33 (62.3%) in male and 20 (62.5%) in female children and was statistically insignificant (P = 0.98).
|Table 1: Age distribution of respiratory syncytial virus- positive and respiratory syncytial virus -negative cases|
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Clinical profile of 85 patients in the study population as coryza, wheezing, crepitations, and rhonchi in both RSV-positive and RSV-negative groups was comparable and there was not any statistically significant association between RSV-positive infection and clinical signs and symptoms [Table 2].
|Table 2: Association of respiratory syncytial virus lower respiratory tract infections with demographic, clinical, and radiological findings|
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In 85 patients of the study population, the radiological features were extremely variable. The frequency of presence of infiltrates, hyperinflation, consolidation, consolidation with collapse, consolidation with collapse with hyperinflation, pleural effusion, and normal radiological findings was comparable in both RSV-positive and RSV-negative groups and the difference between the two groups was statistically insignificant [Table 2].
In the 85 patients of the study population, RSV antigen was detected in nasopharyngeal aspirate samples from 53 (62.4%) patients.
| Discussion|| |
RSV is the primary viral etiological agent causing pediatric LRTIs. The peak incidence of RSV-associated LRTIs, severe LRTIs, and RSV-associated hospitalizations is reported in infants <6 months of age. Fattouh et al. have reported 64% RSV-positive patients in their study to be <6 months of age. We also report similar findings with 32 (60.4%) RSV-positive patients in our study belonging to this age group. However, numerically, RSV positivity was comparable in both males and females in our study; some studies have documented a male preponderance of RSV infection while others have suggested a difference in disease severity, with males being more susceptible to severe RSV disease than females.
The clinical manifestations of RSV LRTIs are difficult to distinguish from other forms of viral or bacterial LRTIs due to significant overlap of signs and symptoms with no pathognomic finding. In our study also, no statistically significant correlation could be established between clinical characteristics and RSV infection. Radiological manifestations of RSV infection are reportedly nonspecific and differ in different studies. Kern et al. have reported central pneumonia (32%) and normal X-ray chest (30%) as the most common radiological features in RSV-induced LRTIs. We observed a normal chest radiograph in a majority of RSV-positive patients, and differentiation of RSV-positive and RSV-negative groups on the basis of radiological features was not possible.
In the present study, RSV was detected in 53 (62.4%) children by detecting the RSV fusion protein, employing a chromatographic immunoassay. Employing multiple diagnostic modalities, the reported incidence of RSV LRTIs in Indian pediatric population has varied from 22.1% to 46.6% in various studies., In another study, respiratory RSV was detected in 61 (20.3%) of 301 nasopharyngeal aspirates employing multiplex polymerase chain reaction. We report a very high incidence of 62.4% of RSV-associated LRTIs in our study group. A possible explanation is that different studies have employed different inclusion criteria leading to different incidence of RSV infection. In our study, we exclusively included children aged <2 years (age group most commonly affected by RSV), while other studies where older children up to 5 years of age were included have reported a lower incidence of RSV infection. Moreover, our study was conducted on a wider range of LRTIs including bronchiolitis, wheeze-associated LRTIs, and pneumonia.
Chromatographic immunoassays, though less sensitive and specific than other diagnostic modalities such as direct fluorescent antibody staining, are more user-friendly and do not demand technical time and expertise. These single-step methods serve as “walk away” tests requiring no addition of reagents. They are rapid, reliable, and easy to perform and interpret. Early detection of RSV by these chromatographic immunoassays allows cohorts of infected inpatients to prevent nosocomial transmission of RSV and consideration of appropriate treatment by avoiding unnecessary use of antibiotics. This assay, however, has some limitations: it detects both viable and nonviable RSV particles and inadequate specimen collection, improper handling/transport, or low levels of virus shedding may yield a false-negative result.
| Conclusion|| |
Our data underline that chromatographic immunoassays are valuable diagnostic techniques for rapid identification of RSV in pediatric LRTIs.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Department of Microbiology, Maulana Azad Medical College, New Delhi - 110 002
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]
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