Keywords
Bronchiolitis, Colombia, respiratory syncytial virus, length of hospital stay , chest indrawing
This article is included in the Pathogens gateway.
Bronchiolitis, Colombia, respiratory syncytial virus, length of hospital stay , chest indrawing
The term 'CRP level of more than 40 mg/lit' was clarified in the document and in the tables.There are a typo error, CRP> 40 mg/lit was considered increased. All the corrections suggested by the reviewer were modified.
See the authors' detailed response to the review by Joan L Robinson
See the authors' detailed response to the review by Mauricio T. Caballero
Bronchiolitis is the most frequent lower respiratory tract infection in infants1,2. One of the variables with more incidence in the financial burden of this disease is the hospital length of stay (LOS)3. The hight medical cost associates with prolonged LOS in bronchiolitis imposes an economic burden, especially in tropical middle-income countries4. LOS is a direct measure of the quality of health service5.
Some models have identified predictors of LOS such as age, underlying conditions (congenital heart disease, chronic lung conditions, immunocompromised states), low birthweight, male gender, clinical characteristics at admission, prematurity, detection of RSV6. However, many of these models lack accuracy7 or were made in patients without significant comorbidities8,9. In this context, there is a critical need to explore predictors of LOS, improving their accuracy of current models. This information will allow risk management for healthcare and prioritize care strategies in groups with a high probability of prolonged hospital stay to reduce their impact on hospital costs and morbidity. This study aims to identify clinical variables associated with LOS of bronchiolitis in children in Colombia.
We conducted a retrospective cohort study that included all infants with bronchiolitis younger than two years of age admitted to tertiary centers in Rionegro, Colombia, from January 2019 to December 2019. The municipality of Rionegro had a total population of 101,046 inhabitants, with two tertiary referral hospitals10. Inclusion criteria were defined as children younger than two years of age admitted to the pediatric ward diagnosed with bronchiolitis, according to the national clinical guideline of bronchiolitis (first wheezing episode younger than 24 months of age)11. Patients without lower respiratory compromise, with positive bacterial cultures on admission, confirmed whooping cough (culture or PCR) were excluded. The study protocol was reviewed and approved by the Institutional Review Board of the University of Antioquia (No 18/2015). Informed consent was obtained from all parents or caregivers of the patients included in the study, following the clinical research standards in Colombia, and prior approval by the ethics committee.
We collected the following variables: age, sex, weight, height, signs, and symptoms on admission (including fever, chest indrawing, chest auscultation, %SpO2), vaccination scheduled chart for age, exposure to cigarette smoking, history of prematurity and bronchopulmonary dysplasia confirmed by a neonatologist at the time of discharge from the NICU, comorbidities (congenital heart disease, neurological disease), diagnostic tools as chest X rays, hemograms, etc. Additionally, we collected variables related to outcomes of care or disease-severity parameters such as length of hospital stay. In our hospitals, bronchodilators and systemic steroids are discourage according to national clinical guidelines of bronchiolitis11. Nasopharyngeal aspirate (NPA) was taken immediately upon admission to the emergency department within 48 hrs of admission using standardize technique. RSV was confirmed using direct immunofluorescence (Light Diagnostics TM Respiratory Panel 1 DFA, Merck-Millipore Laboratory). NPA data for other viruses were not available in our institution consistently.
Continuous variables were presented as mean ± standard deviation (SD) or median (interquartile range [IQR]), whichever appropriate. Categorical variables are shown as numbers (percentage). Differences between continuous variables were analyzed using the unpaired t-test or Wilcoxon's signed-rank test, whichever was appropriate. Associations between categorical variables and the outcome variable were analyzed using the chi-square test or Fisher's exact test, as needed. To identify factors independently associated with length of hospital stay, we used a Poisson regression model, or negative binomial regression model in case of the presence of overdispersed count data, to estimate incidence rate ratios (IRR) and adjust for potential confounding variables. We only include initially variables associated with LOS with values of p <0.2 or that change the effect estimate by more than 10% after their inclusion. The variable selection and modeling processes were made following the recommendations of Greenland12. The goodness of fit of the model was evaluated using Hosmer–Lemeshow test and area under curve in Poisson regression or Akaike information criterion (AIC), Bayesian information criterion (BIC) in negative binomial regression. All statistical tests were two-tailed, and the significance level used was p < 0.05. The data were analyzed with Stata v15.0 (Stata Corporation, College Station, TX).
During the study period, 417 cases of bronchiolitis were included. A total of 66% of the patient was less than 6 month, most of them males (60%), with supportive O2 (83%). RSV was detected in 200 patients (48%). Of these, 81 patients had a history of premature birth and 17 of them with BPD. A total of 20 patients had some cardiac or neurological disease and 10 of them with a history of use of palivizumab. Table 1 presents the clinical characteristics of the population. Deidentified individual-level raw data are available from Zenodo13.
Variable | n (%) |
---|---|
Age less than 6 month | 277(66.4) |
Male, n(%) | 251(60.3) |
Premature birth | 81(19.4) |
Comorbidities (CHD or neurological) | 20(4.8) |
BPD | 17(4.0) |
Atopy | 17(4.0) |
Previously hospitalization by bronchiolitis | 30(7.2) |
Exposure to cigarette smoking | 49 (11.9) |
Exclusive maternal breastfeeding for at least six month | 102(24.4) |
%SpO2, median(ds)** | 89(0.2) |
O2 supportive, n(%) | 347(83.4) |
Clinical & laboratory parameters | |
Fever | 119(28.6) |
Chest indrawing | 184(44.2) |
Tachypnea | 48(13.3) |
Rhonchi | 137(32.9) |
Crepitation | 137(32.9) |
Abnormal X-ray* | 109(26.3) |
Leucocytosis (> 15.000/mm3) | 51(12.2) |
RSV positive | 200(48.4) |
Increased C-reactive protein (> 40 mg/lit.) | 327(78.6) |
The median of the length of hospital stay was 3.68 days, with a range of 0.74 days to 29 days and an interquartile range of 4.06 days. Among all 417 patients, 138 (33.1%) have a hospital stay of 5 or more days
Unavariate analysis is presented in Table 2. Due to the significative presence of overdispersed count data was detected (Likelihood-ratio test of alpha=0, χ2= 203.97, p=0.000), a negative binomial regression model was used to adjust for potential confounding variables. The predictive variables included in the complete model were age, sex, premature birth, comorbidities, BPD, atopy, previously hospitalization by bronchiolitis, %SpO2, fever, signs of respiratory distress, RSV, Leucocytosis (>15.000/mm3) and increased C-reactive protein (>40 mg/lit.). After modeling and controlling for potential confounders in the negative binomial regression: age <6 months, comorbidities (CHD or neurological), BPD, chest indrawing, RSV isolation, and C-reactive protein were independent predictors of LOS (Table 3).
Variable. n(%) | n (%) | Incidence rate- ratio (95% CI) | p |
---|---|---|---|
Age less than 6 month | 277(66.4) | 0.998 (0.9-0.9) | 0.000 |
Male , n(%) | 251(60.3) | 0.048 (0.9-1.1) | 0.218 |
Premature birth | 81(19.4) | 1.319 (1.1-1.4) | 0.000 |
Comorbidities (CHD or neurological) | 20(4.8) | 1.787(1.5-2.0) | 0.000 |
BPD | 17(4.0) | 1.037(0.8-1,2) | 0.738 |
Atopy | 17(4.0) | 0.827(0.6-1.0) | 0.123 |
Previously hospitalization by bronchiolitis | 30(7.2) | 0.750(0.6-0.9) | 0.003 |
Exposure to cigarette smoking | 49 (11.9) | 1.040(0.9-1.1) | 0.563 |
Exclusive maternal breastfeeding for at least six month | 102(24.4) | 0.627(0.5-1.0) | 0.423 |
SpO2, median(ds) | 89(0.2) | 1.007(0.9-1.0) | 0.055 |
O2 supportive , n(%) | 347(83.4) | 2.227(1.8-2.6) | 0.000 |
Clinical & laboratory parameters | |||
Fever | 119(28.6) | 0.834(0.7-0.9) | 0.000 |
Chest indrawing | 184(44.2) | 1.416(1.2-1.5) | 0.000 |
Tachypnea | 48(13.3) | 1.181(1.0-1.3) | 0.018 |
Rhonchi | 137(32.9) | 0.777(0.7-0.8) | 0.000 |
Crepitation | 137(32.9) | 1.088(0.9-1.1) | 0.160 |
Abnormal X-ray* | 109(26.3) | 1.055(0.9-1.1) | 0.277 |
Leucocytosis (> 15.000/mm3) | 51(12.2) | 1.179 (1.0-1.3) | 0.010 |
RSV positive | 200(48.4) | 1.653(1.5-1.8) | 0.000 |
Increased C-reactive protein (> 40 mg/lit.) | 327(78.6) | 0.849(0.7-0.9) | 0.002 |
The main purpose of this study was to determine the independent clinical variables associated with LOS of bronchiolitis in children in tropical middle-income countries. Our study shows that RSV, age <6 months, comorbidities (CHD or neurological), BPD, chest indrawing, and C-reactive protein were independent predictors of LOS
Our results emphasize the importance of knowing the presence of RSV. While some predictors of LOS, such as age, comorbidities, and potentially initial signs of respiratory distress, can not be modified, others as detection of RSV are potentially modifiable by interventions such as futures vaccines or palivizumab in a high-risk population14,15. Previous studies in populations with seasonality had revealed the importance of RSV as a predictor of hospital stay. DeVicenzo et al., in a sample of 141 infants <24 months old without previous chronic cardiac or lung disease or prematurity, in Tennessee described a longer LOS with a higher amount of RSV in secretions. A 1-log higher RSV load was associated with a 0.8-day longer hospitalization, reflects the higher RSV load that occur earlier in the disease14. Rodríguez-Martínez, in 303 infants with acute bronchiolitis in Bogota, also found that detection of RSV correlated with a hospital stay of 5 or more days (OR 1.92, CI 95% 1.02 to 3.73)3. In Qatar, Janahi et al., detected RSV in 51.2% of in 369 patients admitted to the pediatric ward for bronchiolitis, but no association was found between RSV and LOS16. Additionally, Masarweh et al., in a retrospective study of 4793 infants with bronchiolitis in a single tertiary medical center in Israel between 2001–2009, found that RSV isolation did not correlate with LOS17. In this evidence, only the Mansbach study used the PCR assay for viral detection, but the results with immunofluorescence assay with respect to the predictive value of RSV were similar to the PCR assay. Indeed, the main problem of the studies mentioned above was the serious statistical mistakes of analyzing the LOS. While we used a negative binomial regression model, due to the presence of overdispersed count data, to adjust for potential confounding variables to analyze LOS, studies by Rodriguez, Devicenzo, and Mansbach dichotomize the LOS to perform logistic regression, while Masarweh's study performed a linear regression; being both approaches not completely correct. The loss of information from dichotomizing a continuous outcome is well documented in the literature, and even worse, analyzing a variable that does not have a normal distribution with a linear regression invalidates this method of analysis18. These pitfalls in statistical analysis can explain the lack of accuracy of predictive models6. The regression models recommended are median, gamma, or Poisson regression, which have some type I error but avoid the mistakes previously mentioned with the logistic or linear regression model.
Othe variable potentially modifiable associated with LOS was age <6 months. Our findings are consistent with previous results reported in the literature and provide further evidence that younger infants are at a greater risk of requiring prolonged LOS3. This can be explained because the smaller caliber of the airways in younger infants and poor innate immune response to RSV in newborns, making younger infants more susceptible to severe forms of viral infections and prolonged LOS19,20. Preventive strategies such as the use of palivizumab in a high-risk population or the use of future vaccines that confer immunity in children under 6 months against RSV; will constitute possibly effective interventions in reducing the economic burden of this disease.
Several predictive models had reports consistently the chest indrawing as predictive of prolonged LOS that is which is biologically plausible and expected due that this sign also is a universal marker of severity of the disease, as well as the presence of underlying conditions (congenital heart disease, chronic lung conditions, immunocompromised states)3,6–8,21–23 or C-reactive protein (CRP) as a biomarker of severity and bacterial co-infection in patients hospitalized for bronchiolitis24–26
Our study has limitations. First, since this study was based on medical records review, we cannot include other variables such as environmental pollution and genetic factors, and residual confounding cannot be excluded. Second, respiratory syncytial virus was confirmed using direct immunofluorescence, which may underestimate the real burden of viral infection. However, despite this possible underestimation, RSV infection was positively associated, and it is possible that the magnitude of the IRR is even greater. The detection of other respiratory viruses was not homogeneous in all patients, so to avoid information bias we decided not to include them in the analysis. We cannot rule out that other respiratory viruses have equal or greater association with our dependent variable in the study. Third, the study was conducted in a tertiary referral hospital, and therefore the patients included represent the high spectrum of severity, limiting the generalization of results to other contexts. However, the similarity of our population in terms of clinical characteristics, risk factors, and seasonality of bronchiolitis in our country with previous reports suggest strength and consistency in our results3,4
Our results show that in infants with bronchiolitis, RSV, age <6 months, comorbidities (CHD or neurological), BPD, chest indrawing, and C-reactive protein were independent predictors of LOS in a tropical middle-income country. As a potentially modifiable risk factor, efforts to reduce the probability of RSV infection can reduce the hight medical cost associates with prolonged LOS in bronchiolitis.
Zenodo: Importance of respiratory syncytial virus as a predictor of hospital length of stay in Bronchiolitis. http://doi.org/10.5281/zenodo.443243413.
This project contains the raw data for each patient assessed in the present study.
Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).
incidence rate ratios (IRR)
hospital length of stay (LOS)
respiratory syncytial virus (RSV)
Nasopharyngeal aspirate (NPA
Bronchopulmonary dysplasia (BPD)
Chronic heart disease (CHD)
All the authors contributed in the same way from conception of the work to the publication of results. All Authors read and approved the manuscript.
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Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Pediatric infectious diseases
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Pediatric infectious diseases
Is the work clearly and accurately presented and does it cite the current literature?
Partly
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
I cannot comment. A qualified statistician is required.
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: pediatric infectious diseases
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Respiratory virus infection in children.
Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
No
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Partly
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Respiratory virus infection in children.
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