Hospitalization for respiratory syncytial virus infection in young children: development of a clinical prediction rule

Global disease burden of and risk factors for acute lower respiratory infections caused by respiratory syncytial virus in preterm infants and young children in 2019: a systematic review and meta-analysis of aggregated and individual participant data

BACKGROUND

Infants and young children born prematurely are at high risk of severe acute lower respiratory infection (ALRI) caused by respiratory syncytial virus (RSV). In this study, we aimed to assess the global disease burden of and risk factors for RSV-associated ALRI in infants and young children born before 37 weeks of gestation.

METHODS

We conducted a systematic review and meta-analysis of aggregated data from studies published between Jan 1, 1995, and Dec 31, 2021, identified from MEDLINE, Embase, and Global Health, and individual participant data shared by the Respiratory Virus Global Epidemiology Network on respiratory infectious diseases. We estimated RSV-associated ALRI incidence in community, hospital admission, in-hospital mortality, and overall mortality among children younger than 2 years born prematurely. We conducted two-stage random-effects meta-regression analyses accounting for chronological age groups, gestational age bands (early preterm, <32 weeks gestational age [wGA], and late preterm, 32 to <37 wGA), and changes over 5-year intervals from 2000 to 2019. Using individual participant data, we assessed perinatal, sociodemographic, and household factors, and underlying medical conditions for RSV-associated ALRI incidence, hospital admission, and three severity outcome groups (longer hospital stay [>4 days], use of supplemental oxygen and mechanical ventilation, or intensive care unit admission) by estimating pooled odds ratios (ORs) through a two-stage meta-analysis (multivariate logistic regression and random-effects meta-analysis). This study is registered with PROSPERO, CRD42021269742.

FINDINGS

We included 47 studies from the literature and 17 studies with individual participant-level data contributed by the participating investigators. We estimated that, in 2019, 1 650 000 (95% uncertainty range [UR] 1 350 000-1 990 000) RSV-associated ALRI episodes, 533 000 (385 000-730 000) RSV-associated hospital admissions, 3050 (1080-8620) RSV-associated in-hospital deaths, and 26 760 (11 190-46 240) RSV-attributable deaths occurred in preterm infants worldwide. Among early preterm infants, the RSV-associated ALRI incidence rate and hospitalisation rate were significantly higher (rate ratio [RR] ranging from 1·69 to 3·87 across different age groups and outcomes) than for all infants born at any gestational age. In the second year of life, early preterm infants and young children had a similar incidence rate but still a significantly higher hospitalisation rate (RR 2·26 [95% UR 1·27-3·98]) compared with all infants and young children. Although late preterm infants had RSV-associated ALRI incidence rates similar to that of all infants younger than 1 year, they had higher RSV-associated ALRI hospitalisation rate in the first 6 months (RR 1·93 [1·11-3·26]). Overall, preterm infants accounted for 25% (95% UR 16-37) of RSV-associated ALRI hospitalisations in all infants of any gestational age. RSV-associated ALRI in-hospital case fatality ratio in preterm infants was similar to all infants. The factors identified to be associated with RSV-associated ALRI incidence were mainly perinatal and sociodemographic characteristics, and factors associated with severe outcomes from infection were mainly underlying medical conditions including congenital heart disease, tracheostomy, bronchopulmonary dysplasia, chronic lung disease, or Down syndrome (with ORs ranging from 1·40 to 4·23).

INTERPRETATION

Preterm infants face a disproportionately high burden of RSV-associated disease, accounting for 25% of RSV hospitalisation burden. Early preterm infants have a substantial RSV hospitalisation burden persisting into the second year of life. Preventive products for RSV can have a substantial public health impact by preventing RSV-associated ALRI and severe outcomes from infection in preterm infants.

FUNDING

EU Innovative Medicines Initiative Respiratory Syncytial Virus Consortium in Europe.

Personalized Infant Risk Prediction for Severe Respiratory Syncytial Virus Lower Respiratory Tract Infection Requiring Intensive Care Unit Admission

Background

Currently, there are no available tools to identify infants at the highest risk of significant morbidity and mortality from respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) who would benefit most from RSV prevention products. The objective was to develop and internally validate a personalized risk prediction tool for use among all newborns that uses readily available birth/postnatal data to predict RSV LRTI requiring intensive care unit (ICU) admission.

Methods

We conducted a population-based birth cohort study of infants born from 1995 to 2007, insured by the Tennessee Medicaid Program, and who did not receive RSV immunoprophylaxis during the first year of life. The primary outcome was severe RSV LRTI requiring ICU admission during the first year of life. We built a multivariable logistic regression model including demographic and clinical variables available at or shortly after birth to predict the primary outcome.

Results

In a population-based sample of 429 365 infants, 713 (0.2%) had severe RSV LRTI requiring ICU admission. The median age of admission was 66 days (interquartile range, 37-120). Our tool, including 19 variables, demonstrated good predictive accuracy (area under the curve, 0.78; 95% confidence interval, 0.77-0.80) and identified infants who did not qualify for palivizumab, based on American Academy of Pediatrics guidelines, but had higher predicted risk levels than infants who qualified (27% of noneligible infants with >0.16% predicted probabilities [lower quartile for eligible infants]).

Conclusions

We developed a personalized tool that identified infants at increased risk for severe RSV LRTI requiring ICU admission, expected to benefit most from immunoprophylaxis.

Risk factors for severe respiratory syncytial virus infection during the first year of life: development and validation of a clinical prediction model

BACKGROUND

Novel immunisation methods against respiratory syncytial virus (RSV) are emerging, but knowledge of risk factors for severe RSV disease is insufficient for optimal targeting of interventions against them. Our aims were to identify predictors for RSV hospital admission from registry-based data and to develop and validate a clinical prediction model to guide RSV immunoprophylaxis for infants younger than 1 year.

METHODS

In this model development and validation study, we studied all infants born in Finland between June 1, 1997, and May 31, 2020, and in Sweden between June 1, 2006, and May 31, 2020, along with the data for their parents and siblings. Infants were excluded if they died or were admitted to hospital for RSV within the first 7 days of life. The outcome was hospital admission due to RSV bronchiolitis during the first year of life. The Finnish study population was divided into a development dataset (born between June 1, 1997, and May 31, 2017) and a temporal hold-out validation dataset (born between June 1, 2017, and May 31, 2020). The development dataset was used for predictor discovery and selection in which we screened 1511 candidate predictors from the infants', parents', and siblings' data, and developed a logistic regression model with the 16 most important predictors. This model was then validated using the Finnish hold-out validation dataset and the Swedish dataset.

FINDINGS

In total, there were 1 124 561 infants in the Finnish development dataset, 130 352 infants in the Finnish hold-out validation dataset, and 1 459 472 infants in the Swedish dataset. In addition to known predictors such as severe congenital heart defects (adjusted odds ratio 2·89, 95% CI 2·28-3·65), we confirmed some less established predictors for RSV hospital admission, most notably oesophageal malformations (3·11, 1·86-5·19) and lower complexity congenital heart defects (1·43, 1·25-1·63). The prediction model's C-statistic was 0·766 (95% CI 0·742-0·789) in Finnish data and 0·737 (0·710-0·762) in Swedish validation data. The infants in the highest decile of predicted RSV hospital admission probability had 4·5 times higher observed risk compared with others. Calibration varied according to epidemic intensity. The model's performance was similar to a machine learning (XGboost) model using all 1511 candidate predictors (C-statistic in Finland 0·771, 95% CI 0·754-0·788). The prediction model showed clinical utility in decision curve analysis and in hypothetical number needed to treat calculations for immunisation, and its C-statistic was similar across different strata of parental income.

INTERPRETATION

The identified predictors and the prediction model can be used in guiding RSV immunoprophylaxis in infants, or as a basis for further immunoprophylaxis targeting tools.

FUNDING

Sigrid Jusélius Foundation, European Research Council, Pediatric Research Foundation, and Academy of Finland.

Clinical and Socioeconomic Burden of Respiratory Syncytial Virus in Iceland

INTRODUCTION

Respiratory syncytial virus (RSV), a very common pathogen, causes variable disease severity. In addition to considerable clinical burden on children, their families and healthcare facilities, RSV infections in children also carry significant direct and indirect socioeconomic burden.

METHODS

We analyzed data from 5 consecutive RSV seasons (2015-2020) and used virologically confirmed RSV infections and age <5 years as case definition. Clinical information was retrieved from electronic patient records. Costs were estimated by assuming an annual 30% attack rate and a combination of direct medical costs and calculations of societal costs of lost productivity.

RESULTS

A total of 716 children younger than 5 years of age had confirmed RSV infection of which 254 needed hospitalizations, most of whom were previously healthy. The median length of admission was 3.6 days and 13 patients needed intensive care. The hospital admission incidence rate was 2.5/1000 children/year, but 9.1 for children younger than 1 years of age. The total annual cost of RSV was estimated at €4.3 million, of which 10% was direct healthcare costs.

DISCUSSION

The clinical and socioeconomic disease burden of RSV in Iceland is substantial despite slightly lower hospital admission rates than other high-income countries. The prevention of RSV in young children, either through maternal or infant vaccination, has the potential to decrease both clinical and financial impact of the annual epidemics.

Identifying the Target Population for Primary Respiratory Syncytial Virus Two-Step Prevention in Infants: Normative Outcome of Hospitalisation Assessment for Newborns (NOHAN)

Background: Respiratory syncytial virus (RSV) is the leading cause of acute respiratory infection- related hospitalisations in infants (RSVh). Most of these infants are younger than 6 months old with no known risk factors. An efficient RSVh prevention program should address both mothers and infants, relying on Non-Pharmaceutical (NPI) and Pharmaceutical Interventions (PI). This study aimed at identifying the target population for these two interventions. Methods: Laboratory-confirmed RSV-infected infants hospitalised during the first 6 months of life were enrolled from the Hospices Civils de Lyon birth cohort (2014 to 2018). Clinical variables related to pregnancy and birth (sex, month of birth, birth weight, gestational age, parity) were used for descriptive epidemiology, multivariate logistic regression, and predictive score development. Results: Overall, 616 cases of RSVh in 45,648 infants were identified. Being born before the epidemic season, prematurity, and multiparity were independent predictors of RSVh. Infants born in January or June to August with prematurity and multiparity, and those born in September or December with only one other risk factor (prematurity or multiparity) were identified as moderate-risk, identifying the mothers as candidates for a first-level NPI prevention program. Infants born in September or December with prematurity and multiparity, and those born in October or November were identified as high-risk, identifying the mothers and infants as candidates for a second-level (NPI and PI) intervention. Conclusions: It is possible to determine predictors of RSVh at birth, allowing early enrollment of the target population in a two-level RSV prevention intervention.

Predictors of poor outcomes of respiratory syncytial virus acute lower respiratory infections in children under 5 years of age in a middle-income tropical country based on the National Public Health Surveillance System

OBJECTIVES

The aim of the present study is to gain insight into the identification of region-specific factors associated with poor outcomes in children under 5 years of age with confirmed respiratory syncytial virus acute lower respiratory infection (RSV-ALRI) living in Colombia, a middle-income country, based on the National Public Health Surveillance System of the country.

METHODS

An analytical cross-sectional study was conducted using epidemiological data from the records of morbidity and mortality of respiratory infections as registered in the surveillance system report of the National Institute of Health of Colombia 2018, including children under 5 years of age with confirmed RSV-ALRI. Predictor variables included demographic and clinical variables, as well as variables measured after hospital attendance. Outcome variables analyzed were respiratory failure, the need for pediatric intensive care unit admission, and mortality.

RESULTS

Of a total of 8470 patients with a diagnosis of ALRI, we selected 1215 (14.3%) that were under 5 years of age and were positive for RSV. After controlling for potential confounders, it was found that age, gender, socioeconomic stratum, incomplete pneumococcal conjugate vaccine 13 immunization for age, cardiac disease, and malnutrition as comorbidities, chest X-ray findings, and development of sepsis independently predicted poor outcomes among the patients analyzed.

CONCLUSIONS

The identified predictors for poor outcomes in RSV-affected children may be helpful for guiding efficient and targeted national and/or regional programs and public policies to assist in achieving Goal 3 of the Sustainable Development Goals adopted by the United Nations in 2015.

Respiratory Syncytial Virus-Associated Hospital Admissions and Bed Days in Children <5 Years of Age in 7 European Countries

BACKGROUND

Respiratory syncytial virus (RSV) is a leading cause of respiratory tract infections (RTIs) in young children. High-quality country-specific estimates of bed days and length of stay (LOS) show the population burden of RSV-RTI on secondary care services and the burden among patients, and can be used to inform RSV immunization implementation decisions.

METHODS

We estimated the hospital burden of RSV-associated RTI (RSV-RTI) in children under 5 years in 7 European countries (Finland, Denmark, Norway, Scotland, England, the Netherlands, and Italy) using routinely collected hospital databases during 2001-2018. We described RSV-RTI admission rates during the first year of life by birth month and assessed their correlation with RSV seasonality in 5 of the countries (except for England and Italy). We estimated average annual numbers and rates of bed days for RSV-RTI and other-pathogen RTI, as well as the hospital LOS.

RESULTS

We found that infants born 2 months before the peak month of RSV epidemics more frequently had the highest RSV-RTI hospital admission rate. RSV-RTI hospital episodes accounted for 9.9-21.2 bed days per 1000 children aged <5 years annually, with the median (interquartile range) LOS ranging from 2 days (0.5-4 days) to 4 days (2-6 days) between countries. Between 70% and 89% of these bed days were in infants aged <1 year, representing 40.3 (95% confidence interval [CI], 40.1-40.4) to 91.2 (95% CI, 90.6-91.8) bed days per 1000 infants annually. The number of bed days for RSV-RTI was higher than that for RTIs associated with other pathogens in infants aged <1 year, especially in those <6 months.

CONCLUSIONS

RSV disease prevention therapies (monoclonal antibodies and maternal vaccines) for infants could help prevent a substantial number of bed days due to RSV-RTI. "High-risk" birth months should be considered when developing RSV immunization schedules. Variation in LOS between countries might reflect differences in hospital care practices.

Developing a prediction model to estimate the true burden of respiratory syncytial virus (RSV) in hospitalised children in Western Australia

Respiratory syncytial virus (RSV) is a leading cause of childhood morbidity, however there is no systematic testing in children hospitalised with respiratory symptoms. Therefore, current RSV incidence likely underestimates the true burden. We used probabilistically linked perinatal, hospital, and laboratory records of 321,825 children born in Western Australia (WA), 2000-2012. We generated a predictive model for RSV positivity in hospitalised children aged < 5 years. We applied the model to all hospitalisations in our population-based cohort to determine the true RSV incidence, and under-ascertainment fraction. The model's predictive performance was determined using cross-validated area under the receiver operating characteristic (AUROC) curve. From 321,825 hospitalisations, 37,784 were tested for RSV (22.8% positive). Predictors of RSV positivity included younger admission age, male sex, non-Aboriginal ethnicity, a diagnosis of bronchiolitis and longer hospital stay. Our model showed good predictive accuracy (AUROC: 0.87). The respective sensitivity, specificity, positive predictive value and negative predictive values were 58.4%, 92.2%, 68.6% and 88.3%. The predicted incidence rates of hospitalised RSV for children aged < 3 months was 43.7/1000 child-years (95% CI 42.1-45.4) compared with 31.7/1000 child-years (95% CI 30.3-33.1) from laboratory-confirmed RSV admissions. Findings from our study suggest that the true burden of RSV may be 30-57% higher than current estimates.

Risk factors associated with severe disease in respiratory syncytial virus infected children under 5 years of age

OBJECTIVE

To evaluate risk factors for severe disease in children under 59 months of age hospitalized with respiratory syncytial virus (RSV) infection.

STUDY DESIGN

We prospectively enrolled 1,096 cases of laboratory confirmed RSV infection during three consecutive RSV seasons in 2015-2018. Potential risk factors for severe disease were retrieved through patient questionnaires and linkage to national health registries. Need for respiratory support (invasive ventilation, bi-level positive airway pressure, or continuous positive airway pressure), and length of stay exceeding 72 h were used as measures of disease severity. Associations were investigated using multivariable logistic regression analyses. Multiple imputation was used to avoid bias and inference induced by missing data.

RESULTS

Risk factors associated with a need for respiratory support included age younger than 3 months of age [aOR: 6.73 (95% CI 2.71-16.7)], having siblings [aOR: 1.65 (95% CI 1.05-2.59)] and comorbidity [aOR: 2.40 (95% CI 1.35-4.24)]. The length of hospital stay >72 h was significantly associated with being younger than 3 months of age [aOR: 3.52 (95% CI 1.65-7.54)], having siblings [aOR: 1.45 (95% CI 1.01-2.08)], and comorbidity [aOR: 2.18 (95% CI 1.31-3.61)]. Sub-group analysis of children younger than 6 months of age confirmed the association between both young age and having siblings and the need for respiratory support.

CONCLUSION

In a large cohort of children <59 months hospitalized with RSV infection, young age, comorbidity, and having siblings were associated with more severe disease.

Respiratory Syncytial Virus-Associated Acute Lower Respiratory Infections in Children With Bronchopulmonary Dysplasia: Systematic Review and Meta-Analysis

BACKGROUND

Respiratory syncytial virus (RSV) is among the most important causes of acute lower respiratory tract infection (ALRI) in young children. We assessed the severity of RSV-ALRI in children less than 5 years old with bronchopulmonary dysplasia (BPD).

METHODS

We searched for studies using EMBASE, Global Health, and MEDLINE. We assessed hospitalization risk, intensive care unit (ICU) admission, need for oxygen supplementation and mechanical ventilation, and in-hospital case fatality (hCFR) among children with BPD compared with those without (non-BPD). We compared the (1) length of hospital stay (LOS) and (2) duration of oxygen supplementation and mechanical ventilation between the groups.

RESULTS

Twenty-nine studies fulfilled our inclusion criteria. The case definition for BPD varied substantially in the included studies. Risks were higher among children with BPD compared with non-BPD: RSV hospitalization (odds ratio [OR], 2.6; 95% confidence interval [CI], 1.7-4.2; P < .001), ICU admission (OR, 2.9; 95% CI, 2.3-3.5; P < .001), need for oxygen supplementation (OR, 4.2; 95% CI, .5-33.7; P = .175) and mechanical ventilation (OR, 8.2; 95% CI, 7.6-8.9; P < .001), and hCFR (OR, 12.8; 95% CI, 9.4-17.3; P < .001). Median LOS (range) was 7.2 days (4-23) (BPD) compared with 2.5 days (1-30) (non-BPD). Median duration of oxygen supplementation (range) was 5.5 days (0-21) (BPD) compared with 2.0 days (0-26) (non-BPD). The duration of mechanical ventilation was more often longer (>6 days) in those with BPD compared with non-BPD (OR, 11.9; 95% CI, 1.4-100; P = .02).

CONCLUSIONS

The risk of severe RSV disease is considerably higher among children with BPD. There is an urgent need to establish standardized BPD case definitions, review the RSV prophylaxis guidelines, and encourage more specific studies on RSV infection in BPD patients, including vaccine development and RSV-specific treatment.

Predictors and incidence of hospitalization due to respiratory syncytial virus (RSV)-associated lower respiratory tract infection (LRTI) in non-prophylaxed moderate-to-late preterm infants in Bosnia and Herzegovina

Prematurity is a risk factor for respiratory syncytial virus (RSV)-associated lower respiratory tract infections (LRTIs), due to immature humoral and cell-mediated immune system in preterm newborns, as well as their incomplete lung development. Palivizumab, a humanized monoclonal antibody against the F glycoprotein of RSV, is licensed for the prevention of severe RSV LRTI in children at high risk for the disease. This study is a part of a larger observational, retrospective-prospective epidemiological study (PONI) conducted at 72 sites across 23 countries in the northern temperate zone. The aim of our non-interventional study was to identify common predictors and factors associated with RSV LRTI hospitalization in non-prophylaxed, moderate-to-late preterm infants, born between 33 weeks and 0 days and 35 weeks and 6 days of gestation, and less than 6 months prior to or during the RSV season in Bosnia and Herzegovina (B&H). A total of 160 moderate-to-late preterm infants were included from four sites in B&H (Sarajevo, Tuzla, Mostar, and Banja Luka). We identified several significant intrinsic and extrinsic factors to be associated with the risk of RSV LRTI hospitalization in the preterm infants, including: comorbidities after birth, shorter hospital stay, admission to NICU/PICU while in the maternity ward, household smoking, low maternal age, breast feeding, number of family members, and history of family/paternal atopy. Overall, our results indicated that the risk of RSV LRTI in preterm newborns can be associated with different environmental and social/cultural factors, and further research is needed to comprehensively evaluate these associations.

Prospective observational study in two Dutch hospitals to assess the performance of inflammatory plasma markers to determine disease severity of viral respiratory tract infections in children

INTRODUCTION

Respiratory viruses causing lower respiratory tract infections (LRTIs) are a major cause of hospital admissions in children. Since the course of these infections is unpredictable with potential fast deterioration into respiratory failure, infants are easily admitted to the hospital for observation. The aim of this study was to examine whether systemic inflammatory markers can be used to predict severity of disease in children with respiratory viral infections.

METHODS

Blood and nasopharyngeal washings from children <3 years of age with viral LRTI attending a hospital were collected within 24 hours (acute) and after 4-6 weeks (recovery). Patients were assigned to a mild (observation only), moderate (supplemental oxygen and/or nasogastric feeding) or severe (mechanical ventilation) group. Linear regression analysis was used to design a prediction rule using plasma levels of C reactive protein (CRP), serum amyloid A (SAA), pentraxin 3 (PTX3), serum amyloid P component and properdin. This rule was tested in a validation cohort.

RESULTS

One hundred and four children (52% male) were included. A combination of CRP, SAA, PTX3 and properdin was a better indicator of severe disease compared with any of the individual makers and age (69% sensitivity (95% CI 50 to 83), 90% specificity (95% CI 80 to 96)). Validation in 141 patients resulted in 71% sensitivity (95% CI 53 to 85), 87% specificity (95% CI 79 to 92), negative predictive value of 64% (95% CI 47 to 78) and positive predictive value of 90% (95% CI 82 to 95). The prediction rule was not able to identify patients with a mild course of disease.

CONCLUSION

A combination of CRP, SAA, PTX3 and properdin was able to identify children with a severe course of viral LRTI disease, even in children under 2 months of age. To assess the true impact on clinical management, these results should be validated in a prospective randomised control study.

Potential Cost-Effectiveness of RSV Vaccination of Infants and Pregnant Women in Turkey: An Illustration Based on Bursa Data

Background

Worldwide, respiratory syncytial virus (RSV) is considered to be the most important viral cause of respiratory morbidity and mortality among infants and young children. Although no active vaccine is available on the market yet, there are several active vaccine development programs in various stages. To assess whether one of these vaccines might be a future asset for national immunization programs, modeling the costs and benefits of various vaccination strategies is needed.

Objectives

To evaluate the potential cost-effectiveness of RSV vaccination of infants and/or pregnant women in Turkey.

Methods

A multi-cohort static Markov model with cycles of one month was used to compare the cost-effectiveness of vaccinated cohorts versus non-vaccinated cohorts. The 2014 Turkish birth cohort was divided by twelve to construct twelve monthly birth cohorts of equal size (111,459 new-borns). Model input was based on clinical data from a multicenter prospective study from Bursa, Turkey, combined with figures from the (inter)national literature and publicly available data from the Turkish Statistical Institute (TÜÏK). Incremental cost-effectiveness ratios (ICERs) were expressed in Turkish Lira (TL) per quality-adjusted life year (QALY) gained.

Results

Vaccinating infants at 2 and 4 months of age would prevent 145,802 GP visits, 8,201 hospitalizations and 48 deaths during the first year of life, corresponding to a total gain of 1650 QALYs. The discounted ICER was estimated at 51,969 TL (26,220 US $ in 2013) per QALY gained. Vaccinating both pregnant women and infants would prevent more cases, but was less attractive from a pure economic point of view with a discounted ICER of 61,653 TL (31,106 US $ in 2013) per QALY. Vaccinating only during pregnancy would result in fewer cases prevented than infant vaccination and a less favorable ICER.

Conclusion

RSV vaccination of infants and/or pregnant women has the potential to be cost-effective in Turkey. Although using relatively conservative assumptions, all evaluated strategies remained slightly below the threshold of 3 times the GDP per capita.

Estimating Respiratory Syncytial Virus-associated Hospitalization in the First Year of Life Among Infants Born at 32-35 Weeks of Gestation

BACKGROUND

Prophylaxis against respiratory syncytial virus-associated hospitalization (RSV-H) with anti-RSV monoclonal antibody is not considered cost-effective for routine use in most jurisdictions. The aim of this study was to develop a scoring tool to estimate local risk of RSV-H in the first year of life among moderately premature infants to assist in prophylaxis decision making.

METHODS

A retrospective cohort was constructed from population-based databases in Nova Scotia, Canada, to follow 32- to 35-week gestation infants from the prenatal period to <12 months of age, from 1998 to 2008. Potential risk factors were entered into the logistic regression model, where the dependent variable was RSV-H. Receiver operator characteristic analysis demonstrated cutoff scores producing the highest predictive accuracy, and the likelihood ratio test was used to select the final set of variables for the predictive tool.

RESULTS

In 2811 eligible infants, the overall RSV-H rate was 3.1% (88/2811). Of 17 variables considered, 3 were used to create the scoring tool: birth during December to February, household smoke exposure and household crowding. The positive likelihood ratios of predictive tool scores for high, moderate and low of RSV-H were 3.57, 3.38 and 1.95, whereas posttest probabilities (risk of RSV-H) were 11.4%, 10.8% and 1.6%, respectively.

CONCLUSIONS

While able to predict infants at low risk of RSV-H, the tool did not discriminate high from moderate risk infants. The tool could be used in anticipatory care to help educate families about reducing risk of serious RSV illness in their newborn.

Risk factors for respiratory syncytial virus associated with acute lower respiratory infection in children under five years: Systematic review and meta-analysis

Background

Respiratory syncytial virus (RSV) is the most common pathogen identified in young children with acute lower respiratory infection (ALRI) as well as an important cause of hospital admission. The high incidence of RSV infection and its potential severe outcome make it important to identify and prioritise children who are at higher risk of developing RSV–associated ALRI. We aimed to identify risk factors for RSV–associated ALRI in young children.

Methods

We carried out a systematic literature review across 4 databases and obtained unpublished studies from RSV Global Epidemiology Network (RSV GEN) collaborators. Quality of all eligible studies was assessed according to modified GRADE criteria. We conducted meta–analyses to estimate odds ratios with 95% confidence intervals (CI) for individual risk factors.

Results

We identified 20 studies (3 were unpublished data) with “good quality” that investigated 18 risk factors for RSV–associated ALRI in children younger than five years old. Among them, 8 risk factors were significantly associated with RSV–associated ALRI. The meta–estimates of their odds ratio (ORs) with corresponding 95% confidence intervals (CI) are prematurity 1.96 (95% CI 1.44–2.67), low birth weight 1.91 (95% CI 1.45–2.53), being male 1.23 (95% CI 1.13–1.33), having siblings 1.60 (95% CI 1.32–1.95), maternal smoking 1.36 (95% CI 1.24–1.50), history of atopy 1.47 (95% CI 1.16–1.87), no breastfeeding 2.24 (95% CI 1.56–3.20) and crowding 1.94 (95% CI 1.29–2.93). Although there were insufficient studies available to generate a meta–estimate for HIV, all articles (irrespective of quality scores) reported significant associations between HIV and RSV–associated ALRI.

Conclusions

This study presents a comprehensive report of the strength of association between various socio–demographic risk factors and RSV–associated ALRI in young children. Some of these amenable risk factors are similar to those that have been identified for (all cause) ALRI and thus, in addition to the future impact of novel RSV vaccines, national action against ALRI risk factors as part of national control programmes can be expected to reduce burden of disease from RSV. Further research which identifies, accesses and analyses additional unpublished RSV data sets could further improve the precision of these estimates.

Preventing hospitalizations for respiratory syncytial virus infection

Respiratory syncytial virus infection is the leading cause of lower respiratory tract infections in young children. Palivizumab has minimal impact on RSV hospitilization rates as it is only practical to offer it to the highest risk groups. The present statement reviews the published literature and provides updated recommendations regarding palivizumab use in children in Canada.

Human bocavirus infection as a cause of severe acute respiratory tract infection in children

In 2005 human bocavirus (HBoV) was discovered in respiratory tract samples of children. The role of HBoV as the single causative agent for respiratory tract infections remains unclear. Detection of HBoV in children with respiratory disease is frequently in combination with other viruses or bacteria. We set up an algorithm to study whether HBoV alone can cause severe acute respiratory tract infection (SARI) in children. The algorithm was developed to exclude cases with no other likely cause than HBoV for the need for admission to the paediatric intensive care unit (PICU) with SARI. We searched for other viruses by next-generation sequencing (NGS) in these cases and studied their HBoV viral loads. To benchmark our algorithm, the same was applied to respiratory syncytial virus (RSV)-positive patients. From our total group of 990 patients who tested positive for a respiratory virus by means of RT-PCR, HBoV and RSV were detected in 178 and 366 children admitted to our hospital. Forty-nine HBoV-positive patients and 72 RSV-positive patients were admitted to the PICU. We found seven single HBoV-infected cases with SARI admitted to PICU (7/49, 14%). They had no other detectable virus by NGS. They had much higher HBoV loads than other patients positive for HBoV. We identified 14 RSV-infected SARI patients with a single RSV infection (14/72, 19%). We conclude that our study provides strong support that HBoV can cause SARI in children in the absence of viral and bacterial co-infections.

RSV infection among children born moderately preterm in a community-based cohort

We aimed to determine the rates of proven respiratory syncytial virus (RSV) hospitalization and disease severity among children born moderately preterm (MP, gestational age [GA] 32-36 weeks, n = 964), children born full-term (FT, GA 38-42 weeks, n = 572), and children born early preterm (EP, GA <32 weeks, n = 524). Our second aim was to identify risk factors for RSV hospitalization among MP. We extracted data from parental questionnaires and medical records, retrieved from a community-based cohort of children aged 43-49 months. The RSV hospitalization rates of MP were higher than FT (3.9 vs. 1.2 %, relative rate 3.2; 95 % confidence interval (CI) 1.4-7.1) and equal to EP (3.9 vs. 3.2 %, relative rate 1.2; 95 % CI 0.7-2.1). MP were hospitalized at an earlier age than EP. Disease severity (based on the type of treatment and hospitalization length) was equal in all groups. Risk factors for RSV hospitalization in MP were younger age and lower birth weight. In multivariable analyses, shorter GA and passive smoking independently increased the likelihood of RSV hospitalization in MP.

CONCLUSION

The rates of hospitalization due to proven RSV infection are higher in MP than FT and not different between MP and EP. No difference in disease severity was observed. Among MP, the rates of RSV hospitalization are higher for lower GA and when exposed to passive smoking.

Nasopharyngeal gene expression, a novel approach to study the course of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) causes mild infections in the vast majority of children. However, in some cases, it causes severe disease, such as bronchiolitis and pneumonia. Development of severe RSV infection is determined by the host response. Therefore, the main aim of this study was to identify biomarkers associated with severe RSV infection. To identify biomarkers, nasopharyngeal gene expression was profiled by microarray studies, resulting in the selection of five genes: ubiquitin D, tetraspanin 8, mucin 13, β-microseminoprotein and chemokine ligand 7. These genes were validated by real-time quantitative PCR in an independent validation cohort, which confirmed significant differences in gene expression between mildly and severely infected and between recovery and acute patients. Nasopharyngeal aspirate samples are regularly taken when a viral respiratory tract infection is suspected. In this article, we describe a method to discriminate between mild and severe RSV infection based on differential host gene expression. The combination of pathogen detection and host gene expression analysis in nasopharyngeal aspirates will significantly improve the diagnosis and prognosis of respiratory tract infections.

A systematic review of predictive modeling for bronchiolitis

PURPOSE

Bronchiolitis is the most common cause of illness leading to hospitalization in young children. At present, many bronchiolitis management decisions are made subjectively, leading to significant practice variation among hospitals and physicians caring for children with bronchiolitis. To standardize care for bronchiolitis, researchers have proposed various models to predict the disease course to help determine a proper management plan. This paper reviews the existing state of the art of predictive modeling for bronchiolitis. Predictive modeling for respiratory syncytial virus (RSV) infection is covered whenever appropriate, as RSV accounts for about 70% of bronchiolitis cases.

METHODS

A systematic review was conducted through a PubMed search up to April 25, 2014. The literature on predictive modeling for bronchiolitis was retrieved using a comprehensive search query, which was developed through an iterative process. Search results were limited to human subjects, the English language, and children (birth to 18 years).

RESULTS

The literature search returned 2312 references in total. After manual review, 168 of these references were determined to be relevant and are discussed in this paper. We identify several limitations and open problems in predictive modeling for bronchiolitis, and provide some preliminary thoughts on how to address them, with the hope to stimulate future research in this domain.

CONCLUSIONS

Many problems remain open in predictive modeling for bronchiolitis. Future studies will need to address them to achieve optimal predictive models.

Clinical characteristics and direct medical cost of respiratory syncytial virus infection in children hospitalized in Suzhou, China

BACKGROUND

There have been few studies on children hospitalized with respiratory syncytial virus (RSV) published from mainland China. We performed a retrospective review of medical charts to describe the epidemiology, clinical features and direct medical cost of laboratory-proven RSV children hospitalized in Suzhou, China.

METHODS

Testing is routine for RSV for children admitted to the respiratory ward at Suzhou University Children's Hospital. We performed a retrospective study on children with documented RSV infection hospitalized at Suzhou University Children Hospital during 2005-2009 using a structured chart review instrument.

RESULTS

A total of 2721 hospitalized children (15.0% of those tested) were positive by immunofluorescent assay for RSV during 2005-2009, and 64.0% of them were male. Eighty-seven percentage of the RSV-infected children were 2 years old and younger, and 56.6% were ≤ 6 months of age. The median length of hospital stay was 8 days. Of the RSV-infected children, 92.5% developed pneumonia and 21.8% experienced wheezing. In total, 49 (5.1%) of RSV-positive children were transferred to the ICU. Children ≤ 6 months old and who had congenital heart disease had higher risk of severe RSV disease. The mean cost of each RSV-related hospitalization was US$571.8 (US$909.6 for children referred to ICU and US$565.4 for those cared for on the wards). Multivariable logistic regression showed that compared with the ≤ 6 months children, those aged >6 months old had higher hospitalization cost; children with respiratory distress or with chronic lung diseases tended to have higher hospitalization costs than others.

CONCLUSIONS

RSV infections and severe RSV diseases mostly occurred in early infancy. The direct medical cost was high relative to family income. Effective strategies of RSV immunization of young children in China may be beneficial in addressing this disease burden.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

A cost-effectiveness analysis of respiratory syncytial virus (RSV) prophylaxis in infants in the United Kingdom

BACKGROUND

Respiratory syncytial virus (RSV) is a common cause of respiratory infection that is highly prevalent in infants. Severe cases of RSV infection require hospitalisation; this is most likely to occur in infant populations at high risk. The study assesses the cost-effectiveness of palivizumab versus no prophylaxis in infants at high risk of hospitalisation with RSV in the United Kingdom (UK).

METHODS

A decision tree model was developed to reflect the clinical pathway of infants at high risk of severe RSV infection who receive either prophylaxis with palivizumab or no prophylaxis. The main outcome was the incremental cost-effectiveness ratio (ICER). One-way and probabilistic sensitivity analyses were performed to assess the degree of uncertainty surrounding the results. A threshold analysis considered the impact of clinical and environmental risk factors on the cost-effectiveness in the subgroup of preterm infants 33-35 weeks gestational age (wGA).

RESULTS

Prophylaxis with palivizumab compared with no prophylaxis is associated with the following ICERs; £33,216 for infants with congenital heart disease; £19,168 for infants with chronic lung disease; £3,845 for preterm infants < 29 wGA; £30,205 for preterm infants 29-32 wGA; and £99,056 for preterm infants 33-35 wGA. One-way sensitivity analysis suggests that these results are highly sensitive to the input data. Threshold analysis in the preterm 33-35 wGA subgroup demonstrates that an adjusted RSV-hospitalisation baseline risk of 17.94% or higher would result in an ICER below the £30,000 per quality-adjusted life-year threshold.

DISCUSSION

Palivizumab is cost-effective compared to no prophylaxis in the United Kingdom in many of the subgroups considered, showing that palivizumab would be a cost-effective use of National Health Service resources.

Infectious burden of respiratory syncytial virus in relation to time of birth modifies the risk of lower respiratory tract infection in infancy: the Norwegian Mother and Child Cohort

OBJECTIVE

The risk of respiratory syncytial virus (RSV) infection according to calendar month of birth has previously been demonstrated. We hypothesize that the real-time infectious burden (IB) of RSV, in relation to time and county of birth, modifies the risk of lower respiratory tract infection (LRTI) in infants, an association that has not been investigated previously, and may be used as an alternative measure of RSV risk when drafting RSV immunoprophylaxis guidelines.

METHODS

Thirty thousand eighty-seven pregnancies were included from July 1, 2003, to July 31, 2006. IB was defined by month and county as the number of RSV detections per inhabitant. IB for 5 periods ante- and postnatally was calculated for each child. Outcome variables were maternally reported hospitalization for LRTI before age 6 months and LRTI before age 12 months. Logistic regression was used to estimate associations between IB and LRTI.

RESULTS

The odds of hospitalization for LRTI rise with increased IB the first 3 months after birth. Low IB: odds ratio (OR) 1.17 (95% confidence interval [CI]: 0.98-1.39); medium IB: OR 1.42 (95% CI: 1.21-1.68); high IB: OR 2.51 (95% CI: 2.15-2.94). High IB 3-0 months before birth confers a lower odds of hospitalization for LRTI the first 6 months of life, OR 0.51 (95% CI: 0.43-0.61). Similar results were seen for maternally reported LRTI the first 12 months of life.

CONCLUSIONS

We find an association between real-time RSV infectious burden and LRTI in infancy: high burden before birth is protective and high burden after birth increases the risk.

Prospective multicenter study of children with bronchiolitis requiring mechanical ventilation

OBJECTIVE

To identify factors associated with continuous positive airway pressure (CPAP) and/or intubation for children with bronchiolitis.

METHODS

We performed a 16-center, prospective cohort study of hospitalized children aged <2 years with bronchiolitis. For 3 consecutive years from November 1 until March 31, beginning in 2007, researchers collected clinical data and a nasopharyngeal aspirate from study participants. We oversampled children from the ICU. Samples of nasopharyngeal aspirate were tested by polymerase chain reaction for 18 pathogens.

RESULTS

There were 161 children who required CPAP and/or intubation. The median age of the overall cohort was 4 months; 59% were male; 61% white, 24% black, and 36% Hispanic. In the multivariable model predicting CPAP/intubation, the significant factors were: age <2 months (odds ratio [OR] 4.3; 95% confidence interval [CI] 1.7-11.5), maternal smoking during pregnancy (OR 1.4; 95% CI 1.1-1.9), birth weight <5 pounds (OR 1.7; 95% CI 1.0-2.6), breathing difficulty began <1 day before admission (OR 1.6; 95% CI 1.2-2.1), presence of apnea (OR 4.8; 95% CI 2.5-8.5), inadequate oral intake (OR 2.5; 95% CI 1.3-4.3), severe retractions (OR 11.1; 95% CI 2.4-33.0), and room air oxygen saturation <85% (OR 3.3; 95% CI 2.0-4.8). The optimism-corrected c-statistic for the final model was 0.80.

CONCLUSIONS

In this multicenter study of children hospitalized with bronchiolitis, we identified several demographic, historical, and clinical factors that predicted the use of CPAP and/or intubation, including children born to mothers who smoked during pregnancy. We also identified a novel subgroup of children who required mechanical respiratory support <1 day after respiratory symptoms began.

Cost-effectiveness of potential infant vaccination against respiratory syncytial virus infection in The Netherlands

INTRODUCTION

Respiratory syncytial virus (RSV) infection is one of the major causes of respiratory illness in infants, infecting virtually every child before the age of 2 years. Currently, several Phase 1 trials with RSV vaccines in infants are ongoing or have been completed. As yet, no efficacy estimates are available for these vaccine candidates. Nevertheless, cost-effectiveness estimates might be informative to enable preliminary positioning of an RSV vaccine.

METHODS

A decision analysis model was developed in which a Dutch birth cohort was followed for 12 months. A number of potential vaccination strategies were reviewed such as vaccination at specific ages, a two- or three-dosing scheme and seasonal vaccination versus year-round vaccination. The impact of the assumptions made was explored in various sensitivity analyses, including probabilistic analysis. Outcome measures included the number of GP visits, hospitalizations and deaths, costs, quality-adjusted life years and incremental cost-effectiveness ratios (ICERs).

RESULTS

Currently, without vaccination, an annual number of 28,738 of RSV-related GP visits, 1623 hospitalizations, and 4.5 deaths are estimated in children in the age of 0-1 year. The total annual cost to society of RSV in the non-vaccination scenario is €7.7 million (95%CI: 1.7-16.7) and the annual disease burden is estimated at 597 QALYs (95%CI: 133-1319). In case all infants would be offered a potentially safe and effective 3-dose RSV vaccination scheme at the age of 0, 1 and 3 months, the total annual net costs were estimated to increase to €21.2 million, but 544 hospitalizations and 1.5 deaths would be averted. The ICER was estimated at €34,142 (95%CI: € 21,652-€ 87,766) per QALY gained. A reduced dose schedule, seasonal vaccination, and consideration of out-of-pocket expenses all resulted in more favorable ICER values, whereas a reduced vaccine efficacy or a delay in the timing of vaccination resulted in less favorable ICERs.

DISCUSSION

Our model used recently updated estimates on the burden of RSV disease in children and it included plausible utilities. However, due to the absence of clinical trial data, a number of crucial assumptions had to be made related to the characteristics of potential RSV vaccine. The outcomes of our modeling exercise show that vaccination of infants against RSV might be cost-effective. However, clinical trial data are warranted.

Cost-effectiveness analysis of palivizumab among pre-term infant populations covered by Medicaid in the United States

OBJECTIVE

Medicaid infants are at high risk of severe respiratory syncytial virus (RSV) disease. The study objective was to estimate the cost-effectiveness of palivizumab in a Medicaid population.

METHODS

A societal cost-utility analysis was conducted of prophylaxis with palivizumab vs no prophylaxis among four groups of premature infants: (1) <32 weeks gestational age (wGA) and ≤ 6 months chronologic age (CA); (2) 32-34 wGA, ≤ 3 months CA with 2009 American Academy of Pediatrics (AAP) risk factors (RF); (3) 32-35 wGA, ≤ 6 months CA with 2006 AAP RF; and (4) 32-35 wGA, ≤ 6 months CA with ≤ 1 RF. Full dosing of palivizumab was assumed throughout the RSV season (consistent with the FDA-approved label). All costs were in 2010 US dollars. The societal public payer spend for palivizumab was estimated using Medicaid reimbursement methodologies for the top 10 palivizumab-using states in 2010 minus mandatory manufacturer rebates. This study reports the incremental cost-effectiveness ratios (ICERs) in cost per quality-adjusted life-year (QALY) gained. Sensitivity and probabilistic analyses were also conducted.

RESULTS

Palivizumab saved costs and improved QALYs among infants <32 wGA. Palivizumab was cost-effective in infants 32-34 wGA with 2009 AAP RF ($16,037 per QALY) and in infants 32-35 wGA with 2006 AAP RF ($38,244 per QALY). The ICER for infants 32-35 wGA with ≤ 1 RF was $281,892 per QALY. Influential variables in the sensitivity analysis included the background rate of RSV hospitalization, the cost of palivizumab, and the efficacy of palivizumab.

KEY LIMITATIONS

These results are not generalizable to commercially insured infants or infants outside of the US.

CONCLUSIONS

This is the first cost-utility analysis of palivizumab in a Medicaid population. Palivizumab, when dosed consistent with the FDA-approved labeling, was either cost-saving or cost-effective among current guideline-eligible infants in the Medicaid population. Palivizumab did not demonstrate cost-effectiveness in 32-35 wGA infants with ≤ 1 RF.

Bimodal effects of obesity ratio on disease duration of respiratory syncytial virus infection in children

BACKGROUND

Morbid obesity may be associated with hospitalization and possibly death from the 2009 pandemic H1N1 infection, suggesting a yet unknown association between obesity and the severity of viral infections. Thus, we examined association between obesity ratios and duration of disease in children with Respiratory Syncytial Virus (RSV) infection.

METHODS

A retrospective survey of 243 children admitted for bronchitis, bronchiolitis, pneumonia, and those who tested positive for a RSV test, were observed from a single institute in Japan. Primary outcome was set as the total days of wheezing in both the outpatient clinic and during hospitalization. Secondary outcomes were as follows: 1) total days of fever (37.5°C≤) during hospitalization, and 2) days of drip infusion during hospitalization.

RESULTS

When the obesity ratio was 6 and less, days of wheezing showed significant negative association with obesity ratios. In contrast, when the obesity ratio was more than 6, days of wheezing, days of fever during admission and days of drip infusion showed significant positive association with obesity ratios.

CONCLUSIONS

These results suggest that disease duration of RSV infection may be prolonged not only in lean but also in obese children.

Clinical prediction rules for children: a systematic review

CONTEXT

The degree to which clinical prediction rules (CPRs) for children meet published standards is unclear.

OBJECTIVE

To systematically review the quality, performance, and validation of published CPRs for children, compare them with adult CPRs, and suggest pediatric-specific changes to CPR methodology.

METHODS

Medline was searched from 1950 to 2011. Studies were selected if they included the development of a CPR involving children younger than 18 years. Two investigators assessed study quality, rule performance, and rule validation as methodologic standards.

RESULTS

Of 7298 titles and abstracts assessed, 137 eligible studies were identified. They describe the development of 101 CPRs addressing 36 pediatric conditions. Quality standards met in fewer than half of the studies were blind assessment of predictors (47%), reproducibility of predictors (18%), blind assessment of outcomes (42%), adequate follow-up of outcomes (36%), adequate power (43%), adequate reporting of results (49%), and 95% confidence intervals reported (36%). For rule performance, 48% had a sensitivity greater than 0.95, and 43% had a negative likelihood ratio less than 0.1. For rule validation, 76% had no validation, 17% had narrow validation, 8% had broad validation, and none had impact analysis performed. Compared with CPRs for adult health conditions, quality and rule validation seem to be lower.

CONCLUSIONS

Many CPRs have been derived for children, but few have been validated. Relative to adult CPRs, several quality indicators demonstrated weaknesses. Existing performance standards may prove elusive for CPRs that involve children. CPRs for children that are more assistive and less directive and include patients' values and preferences in decision-making may be helpful.

Clinical prediction rule for RSV bronchiolitis in healthy newborns: prognostic birth cohort study

OBJECTIVE

Our goal was to determine predictors of respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) among healthy newborns.

METHODS

In this prospective birth cohort study, 298 healthy term newborns born in 2 large hospitals in the Netherlands were monitored throughout the first year of life. Parents kept daily logs and collected nose/throat swabs during respiratory tract infections. The primary outcome was RSV LRTI, which was defined on the basis of the combination of positive RSV polymerase chain reaction results and acute wheeze or moderate/severe cough.

RESULTS

Of the 298 children, 42 (14%) developed RSV LRTI. Independent predictors for RSV LRTI were day care attendance and/or siblings, high parental education level, birth weight of >4 kg, and birth in April to September. The area under the receiver operating characteristic curve was 0.72 (95% confidence interval: 0.64-0.80). We derived a clinical prediction rule; possible scores ranged from 0 to 5 points. The absolute risk of RSV LRTI was 3% for children with scores of ≤2 (20% of all children) and 32% for children with all 4 factors (scores of 5; 8% of all children). Furthermore, 62% of the children with RSV LRTI experienced wheezing during the first year of life, compared with 36% of the children without RSV LRTI.

CONCLUSIONS

A simple clinical prediction rule identifies healthy newborns at risk of RSV LRTI. Physicians can differentiate between children with high and low risks of RSV LRTI and subsequently can target preventive and monitoring strategies toward children at high risk.

Health-related quality of life in preschool children in five health conditions

Objective

To test the responsiveness of the Infant/Toddler Quality of Life Questionnaire (ITQOL) to five health conditions. In addition, to evaluate the impact of the child’s age and gender on the ITQOL domain scores.

Methods

Observational study of 494 Dutch preschool-aged children with five clinical conditions and 410 healthy preschool children randomly sampled from the general population. The clinical conditions included neurofibromatosis type 1, wheezing illness, bronchiolitis, functional abdominal complaints, and burns. Health-related quality of life (HRQoL) was assessed by a mailed parent-completed ITQOL. Mean ITQOL scale scores for all conditions were compared with scores obtained from the reference sample. The effect of patient’s age and gender on ITQOL scores was assessed using multi-variable regression analysis.

Results

In all health conditions, substantially lower scores were found for several ITQOL scales. The conditions had a variable effect on the type of ITQOL domains and a different magnitude of effect. Scores for ‘physical functioning’, ‘bodily pain’, and ‘general health perceptions’ showed the greatest range. Parental impact scales were equally affected by all conditions. In addition to disease type, the child’s age and gender had an impact on HRQoL.

Conclusions

The five health conditions (each with a distinct clinical profile) affected the ITQOL scales differently. These results indicate that the ITQOL is sensitive to specific characteristics and symptom expression of the childhood health conditions investigated. This insight into the sensitivity of the ITQOL to health conditions with different symptom expression may help in the interpretation of HRQoL results in future applications.

Predictors of respiratory failure among previously healthy children with respiratory syncytial virus infection

BACKGROUND

Respiratory syncytial virus (RSV)-related disease is the leading cause of hospitalization among infants, with approximately 7% to 21% of these patients developing acute respiratory failure.

OBJECTIVE

The aim of this study was to identify clinical variables at initial presentation in the emergency department (ED) that may predict the subsequent need for mechanical ventilation among previously healthy, RSV-infected children who require pediatric intensive care unit (PICU) hospitalization.

STUDY DESIGN

This is a retrospective study of 67 previously healthy, RSV-infected patients admitted from January 1997 to March 2000 to the PICU. The primary outcome for this study was the need for mechanical ventilation. The relationship between clinical variables at initial ED presentation and the need for mechanical ventilation were explored using univariate and multiple logistic regression analysis.

RESULTS

On multivariate analysis, the presence of lethargy (odds ratio [OR], 12.2; P = .005), grunting (OR, 9.3; P = .01), and a Paco(2) 65 mm Hg or greater (OR, 11.8; P = .013) were clinical factors at initial presentation in the ED associated with the subsequent need for mechanical ventilation among the study cohort. A developmental model that included lethargy, grunting, and a Paco(2) of 65 mm Hg or greater performed well as a prediction model. The developmental model had a sensitivity of 71%, specificity of 96%, a positive predictive value of 86%, and a negative predictive value of 91%.

CONCLUSIONS

The presence of lethargy, grunting, and a Paco(2) of 65 mm Hg or greater at initial presentation in the ED were predictive for the subsequent need for mechanical ventilation in previously healthy, RSV-infected children admitted to the PICU.

[Consensus conference on acute bronchiolitis (II): epidemiology of acute bronchiolitis. Review of the scientific evidence]

A review of the evidence on epidemiology, risk factors, etiology and clinical-etiological profile of acute bronchiolitis is presented. The frequency estimates are very heterogeneous; in the population under two years the frequency of admission for bronchiolitis is between 1 and 3.5%, primary care consultations between 4 and 20% and emergency visits between 1 and 2%. The frequency of admissions for respiratory infection by respiratory syncytial virus in the risk population is: in premature infants < or =32 weeks of gestation between 4.4 and 18%, in patients with bronchopulmonary dysplasia between 7.3 and 42%, and in infants with congenital heart disease between 1.6 and 9.8%. The main risk factors are: prematurity, chronic lung disease or bronchopulmonary dysplasia, congenital heart disease and age less than 3-6 months at onset of the epidemic. Other factors are: older siblings or day care attendance, male gender, exposure to smoking, breastfeeding for less than 1-2 months and variables associated with lower socioeconomic status. Respiratory syncytial virus is the dominant etiological agent, constituting just over half the cases (median 56%; interval 27% to 73%). Other viruses implicated, in descending order of frequency, are rhinovirus, adenovirus, metapneumovirus, influenza viruses, parainfluenza, enterovirus and bocavirus. In studies with genomic detection techniques, between 20 and 25% of cases the virus involved is not identified and between 9% and 27% of cases have viral co-infection. Although respiratory syncytial virus bronchiolitis shows more wheezing and retractions, longer duration of respiratory symptoms and oxygen therapy and are associated with lower use of antibiotics. This pattern is associated with the younger age of the patients and does not help us to predict the etiology. In general, the etiological identification is not useful for the management of patients. However, in young infants (<3 months) with febrile bronchiolitis in the hospital environment, conservative management may help these patients and avoid diagnostic and therapeutic procedures.

Comparative costs of hospitalisation among infants at high risk for respiratory syncytial virus lower respiratory tract infection during the first year of life

OBJECTIVE

This retrospective cohort study compared the total cost of hospitalisation due to respiratory syncytial virus (RSV) lower respiratory tract infection (LRI) during the first year of life between late-preterm (33-36 weeks gestational age [wGA]) and term (≥ 37 wGA) infants.

RESEARCH DESIGN AND METHODS

A large national claims database of commercially insured members was examined to identify hospital admissions associated with RSV between January 2003 and June 2007 among infants at high risk for RSV LRI, including late-preterm infants. Hospital use and costs were compared with those of a reference cohort of term infants with RSV.

RESULTS

The cost of hospitalisation for RSV among late-preterm infants with at least one hospital admission associated with RSV (n=173) was twice that of term infants (n=1,983; $20,269 vs. 9,635; p< 0.001). The mean length of stay was also higher (5.3 vs. 3.4 days; p< 0.001). Approximately 21.9% of hospitalisations for late-preterm infants included an intensive care unit admission compared with 9.6% among term infants (p< 0.001).

LIMITATIONS

Reliance on ICD-9 codes to identify potential cohort members may result in misclassification and underreporting the cohort size for conditions of interest.

CONCLUSIONS

Hospitalisation costs and length of stay due to RSV LRI were significantly greater among late-preterm infants compared with term infants and higher than general estimates previously reported in the broader paediatric population.

Excess drug prescriptions during influenza and RSV seasons in the Netherlands: potential implications for extended influenza vaccination

Influenza and respiratory syncytial virus (RSV) infections are responsible for considerable morbidity, mortality and health-care resource use. For the Netherlands, we estimated age and risk-group specific numbers of antibiotics, otologicals and cardiovascular prescriptions per 10,000 person-years during periods with elevated activity of influenza or RSV, and compared these with peri-season rates. Data were taken from the University of Groningen in-house prescription database (www.iadb.nl) and virological surveillance for the period 1998-2006. During influenza and RSV periods excess antibiotic prescriptions were estimated for all age groups. In the age groups 0-1 and 2-4 years, excess antibiotic prescriptions during periods with elevated RSV activity (65% and 59% of peri-seasonal rates) exceeded the surpluses estimated during the influenza-activity periods (24% and 34% of peri-seasonal rates) while for otologicals excess prescriptions were higher for influenza (22% and 27%) than for RSV (14% and 17%). Among persons of 50 years and older, notably those without medical high-risk conditions, excess prescriptions for cardiovascular medications were estimated during the influenza periods at approximately 10% (this was also already seen in persons aged 45-49). Our results may have implications for influenza vaccination policies. In particular, extension of influenza vaccination to groups of non-elderly adults and young children may lower excess prescriptions during these influenza periods for all three types of drug prescriptions investigated.

A predictive model for respiratory syncytial virus (RSV) hospitalisation of premature infants born at 33-35 weeks of gestational age, based on data from the Spanish FLIP Study

BACKGROUND

The aim of this study, conducted in Europe, was to develop a validated risk factor based model to predict RSV-related hospitalisation in premature infants born 33-35 weeks' gestational age (GA).

METHODS

The predictive model was developed using risk factors captured in the Spanish FLIP dataset, a case-control study of 183 premature infants born between 33-35 weeks' GA who were hospitalised with RSV, and 371 age-matched controls. The model was validated internally by 100-fold bootstrapping. Discriminant function analysis was used to analyse combinations of risk factors to predict RSV hospitalisation. Successive models were chosen that had the highest probability for discriminating between hospitalised and non-hospitalised infants. Receiver operating characteristic (ROC) curves were plotted.

RESULTS

An initial 15 variable model was produced with a discriminant function of 72% and an area under the ROC curve of 0.795. A step-wise reduction exercise, alongside recalculations of some variables, produced a final model consisting of 7 variables: birth +/- 10 weeks of start of season, birth weight, breast feeding for < or = 2 months, siblings > or = 2 years, family members with atopy, family members with wheeze, and gender. The discrimination of this model was 71% and the area under the ROC curve was 0.791. At the 0.75 sensitivity intercept, the false positive fraction was 0.33. The 100-fold bootstrapping resulted in a mean discriminant function of 72% (standard deviation: 2.18) and a median area under the ROC curve of 0.785 (range: 0.768-0.790), indicating a good internal validation. The calculated NNT for intervention to treat all at risk patients with a 75% level of protection was 11.7 (95% confidence interval: 9.5-13.6).

CONCLUSION

A robust model based on seven risk factors was developed, which is able to predict which premature infants born between 33-35 weeks' GA are at highest risk of hospitalisation from RSV. The model could be used to optimise prophylaxis with palivizumab across Europe.

Prospective multicenter bronchiolitis study: predicting intensive care unit admissions

OBJECTIVES

The authors sought to identify predictors of intensive care unit (ICU) admission among children hospitalized with bronchiolitis for > or =24 hours.

METHODS

The authors conducted a prospective cohort study during two consecutive bronchiolitis seasons, 2004 through 2006, in 30 U.S. emergency departments (EDs). All included patients were aged <2 years and had a final diagnosis of bronchiolitis. Regular floor versus ICU admissions were compared.

RESULTS

Of 1,456 enrolled patients, 533 (37%) were admitted to the regular floor and 50 (3%) to the ICU. Comparing floor and ICU admissions, multivariate ED predictors of ICU admission were age <2 months (26% vs. 53%; odds ratio [OR] = 4.1; 95% confidence interval [CI] = 2.1 to 8.3), an ED visit the past week (25% vs. 40%; OR = 2.2; 95% CI = 1.1 to 4.4), moderate/severe retractions (31% vs. 48%; OR = 2.6; 95% CI = 1.3 to 5.2), and inadequate oral intake (31% vs. 53%; OR = 3.3; 95% CI = 1.6 to 7.1). Unlike previous studies, no association with male gender, socioeconomic factors, insurance status, breast-feeding, or parental asthma was found with ICU admission.

CONCLUSIONS

In this prospective multicenter ED-based study of children admitted for bronchiolitis, four independent predictors of ICU admission were identified. The authors did not confirm many putative risk factors, but cannot rule out modest associations.

Development and Validation of a Risk Scoring Tool to Predict Respiratory Syncytial Virus Hospitalization in Premature Infants Born at 33 through 35 Completed Weeks of Gestation

Objective. The purpose of the study was to develop and validate a clinical instrument predicting the risk of respiratory syncytial virus (RSV)-associated hospitalization (RSV-H) in premature infants born at 33 through 35 completed weeks of gestation (33— 35GA). Design. An RSV risk scoring tool (RSV-RS) was developed by entering risk factors for RSV-H, determined in a Canadian prospective study, into a multiple logistic regression model. The scoring tool was then validated externally with data from a Spanish case-control study (FLIP). The Canadian cohort comprised 1758 RSV-positive infants born 33— 35GA, of whom 66 (3.7%) had confirmed RSV-H. The FLIP data set comprised 186 (33.4%) RSV-H cases and 371 (66.7%) controls. Method. The primary outcome measure was RSV-H. The RSV-RS score was the sum of the weighted probabilities for each included risk factor multiplied by 100 and ranged from 0 to 100. Receiver operator characteristic curve analyses determined cutoff points to predict subjects at low, moderate, or high RSV-H risk. Results. The RSV-RS included 7 risk factors and cutoff scores of 0— 48, 49— 64, and 65— 100 for low-, moderate-, and high-risk subjects, respectively. For the Canadian cohort, RSV-RS sensitivity in predicting RSV-H cases was 68.2%, with 71.9% specificity. With the FLIP data set, the RSV-RS had lower accuracy (61.3% sensitivity; 65.8% specificity) but showed significant positive association with increased risk for RSV-H. Conclusion. The RSV-RS accurately identified 33— 35GA infants at increased risk for RSV-H in a Canadian cohort. External validation with Spanish case-control study data further confirmed that the scoring tool is appropriate for the estimation of RSV-H risk.

Rate-difference method proved satisfactory in estimating the influenza burden in primary care visits

OBJECTIVE

To compare different methods to estimate the disease burden of influenza, using influenza and respiratory syncytial virus-(RSV) associated primary care data as an example.

STUDY DESIGN AND SETTING

In a retrospective study in the Netherlands over 1997-2003, primary care attended respiratory episodes and national viral surveillance data were used to compare the rate-difference method to other, more complex methods.

RESULTS

The influenza-associated excess estimated by the different methods varied. The estimates provided by the rate-difference model lay well within this range. According to the rate-difference method, influenza-associated primary care consultations were present for all ages, including low-risk adults. The highest influenza-associated burden was demonstrated for children below the age of 5 years. The RSV-associated primary care burden was highest in the youngest age category and well above that associated with influenza. Significant RSV-associated excess was also recorded among adults, particularly in high-risk adults and the elderly.

CONCLUSION

The straightforward rate-difference model seemed satisfactory to estimate the influenza-associated burden. Significant influenza-associated excess was demonstrated among persons not yet recommended for influenza vaccination in The Netherlands. The RSV-associated burden was highest for the youngest children, but also significant for adults.

Prospective multicenter study of bronchiolitis: predicting safe discharges from the emergency department

OBJECTIVE

Bronchiolitis is the leading cause of hospitalization for infants. Our objective was to identify factors associated with safe discharge to home from the emergency department.

METHODS

We conducted a prospective cohort study during 2 consecutive bronchiolitis seasons, from 2004 to 2006. Thirty US emergency departments contributed data. All patients were < 2 years of age and had a final emergency department attending physician diagnosis of bronchiolitis. Using multivariate logistic regression, a low-risk model was developed with a random half of the data and then validated with the other half.

RESULTS

Of 1456 enrolled patients, 837 (57%) were discharged home from the emergency department. The following factors predicted safe discharge to home: age of > or = 2 months, no history of intubation, a history of eczema, age-specific respiratory rates (< 45 breaths per minute for 0-1.9 months, < 43 breaths per minute for 2-5.9 months, and < 40 breaths per minute for 6-23.9 months), no/mild retractions, initial oxygen saturation of > or = 94%, fewer albuterol or epinephrine treatments in the first hour, and adequate oral intake. The importance of each factor varied slightly according to age, but the comprehensive model (developed and validated for all children < 2 years of age) yielded an area under the receiver operating characteristic curve of 0.81, with a good fit of the data.

CONCLUSIONS

This large multicenter study of children presenting to the emergency department with bronchiolitis identified several factors associated with safe discharge, including cut points for respiratory rate and oxygen saturation. Although the low-risk model requires further study, we believe that it will assist clinicians evaluating children with bronchiolitis and may help reduce some unnecessary hospitalizations.

[Severe bronchiolitis. Epidemiology and clinical course of 284 patients]

INTRODUCTION

Bronchiolitis is the leading cause of hospital admission and a frequent cause of pediatric intensive care unit (PICU) admission among infants during the winter months. The objective of this study was to analyze the characteristics and clinical course of patients admitted to the PICU for bronchiolitis.

PATIENTS AND METHOD

We performed a descriptive, observational study by clinical chart review of all patients admitted to the PICU for severe bronchiolitis from November 1994 to March 2006.

RESULTS

A total of 284 patients were included. Most were admitted during December and January and 74% had respiratory syncytial virus (RSV) infection. At least one risk factor for severe disease was present in 68% of the patients: the most frequent risk factor was age < 6 weeks (45%), followed by prematurity (30%). Mechanical ventilation was required in 64 of the 284 patients (24%). Mortality was 1.8% and was associated with chronic pre-existing illness (p < 0.001). The factors associated with a greater risk of mechanical ventilation and a longer PICU stay were the association of two or more risk factors (42/284; 15%), the presence of apnea (73/284; 25.7%), and images of pulmonary consolidation or atelectasis on admission chest X-ray (157/284; 55%).

CONCLUSIONS

Most patients admitted for severe bronchiolitis to the PICU are healthy infants whose principal risk factor is young age. The main predictors of severe clinical course during PICU stay are the association of two or more risk factors, the presence of apnea, and pulmonary consolidation on admission chest X-ray. Bronchiolitis-associated mortality is low and is associated with pre-existing chronic illness.

Palivizumab in congenital heart disease: should international guidelines be revised?

Palivizumab has reduced the incidence of respiratory syncytial virus hospitalization in infants and children with congenital heart disease by 45%. Although the mortality rate of children with congenital heart disease hospitalized with respiratory syncytial virus infection has declined from 37% to approximately 3% over the past 3 decades, palivizumab has not been shown to improve mortality. There has been considerable controversy over the cost-effectiveness of administering palivizumab according to international guidelines, including children with congenital heart disease. In particular, the number of children that need to be treated with palivizumab to prevent one respiratory syncytial virus hospitalization increases dramatically in children > 12 months of age. As a result, the authors recommend that countries re-examine their recommendations for providing palivizumab up to age 24 months in children with congenital heart disease.