1. Texas Pediatric Society Electronic Poster Contest
A simple score to predict length of stay in children hospitalized with RSV bronchiolitis
Manzilat Akande, MD PGY-2, Brinda Mehta, MD, PGY-3, Syeda Nazish Azim, MD, PGY-2 Jaime Fergie, MD.
Driscoll Children’s Hospital, Corpus Christi, TX.
Introduction
(Background)
TABLE 1: Results of Univariate and Multivariate analysis of LOS
RSV Bronchiolitis is the most common lower respiratory infection in children younger than 2 years of age. It leads to more than 100,000 hospitalizations annually in infants, with an estimated cost of over $700 million in Over the past 25 years, hospital admission rates and average length of stay (LOS )for bronchiolitis have increased. Hospital LOS is a simple measure of healthcare quality and hospital performance. It is also recognized as a primary driver of hospitalization costs. We propose that the identification of patient characteristics that predict the duration of hospitalization in children with RSV bronchiolitis may be useful in improving hospital performance.
Abstract
Objective: Every winter RSV infections cause significant morbidity requiring inpatient management. Our study aimed to develop a predictive model for Length of Stay(LOS) in children hospitalized for RSV bronchiolitis and thereby generate a LOS predictive score. Methods: Retrospective cohort of children 2 years or less admitted with laboratory-confirmed RSV infection between December 2009-December Hospital charts of patients with discharge diagnosis of RSV infection by ICD 9 code were reviewed. Median LOS was calculated to define prolonged length of stay. Using logistic regression models predictors of prolonged length of stay was identified. A Length of stay predictor score (LOS) was generated using 4 factors and validated. Results:565 patients were admitted with RSV out of which charts of 370 were analyzed. Univariate and Multivariate logistic regression analysis performed identified 4 factors that strongly predicted length of stay. The factors identified were Presence of documented fever, Age < 6 months , Oxygen saturation < 90% at admission, Use of supplemental Oxygen. Each factor is worth 1 point, except supplemental oxygen which is 2 points. A child with maximum score of 4 had a mean LOS of 6.8 days. Conclusions: Presence of documented fever, age < 6 months, Oxygen saturations < 90% on admission and use of Supplemented Oxygen were the 4 strongest predictors for length of stay in RSV bronchiolitis. This easy to use LOS predictor score may help in identifying those patients with higher risk of longer hospitalization and in turn, optimize inpatient management.
FIG 1: Box plot of LOS by LOS predictor score
Description of Study
TABLE 2: Mean LOS by LOS predictor score group
This was a retrospective chart review of children 2 years and younger admitted with confirmed RSV infection at Driscoll Children’s hospital between December 2009 and December A final sample of 370 subjects was obtained. Data Variables collected were as follows:
Demographic (age, gender, gestational age at birth),
Presence of risk factors known to be associated with severe or complicated disease course (such as CHD, CLD etc),
Clinical (length of stay, Oxygen saturation <90% , PICU admission, documented fever),
Laboratory investigations ( baseline WBC, Blood, urine and CSF cultures) and
Management (IV antibiotic initiation and continuation, Supplemental oxygen).
Median LOS was computed and used to define prolonged hospital stay. Patient demographic and clinical characteristics served as potential independent variables to model hospital LOS.
Univariate and multivariate logistic regression analysis were performed to identify predictors of LOS, which were thereafter used to create a LOS predictor score. ROC curve plots, area under the curve estimated by the c statistic, and the Pearson goodness of fit test were used to validate the predictive model. All tests were 2 tailed and P value < 0.05 was considered significant.
LOS predictor score
 Mean LOS (days)  0
1.75  1
2.6  2
3.5  3
5.3  4
6.8
FIG 2: ROC curve
Conclusions
(Discussion, Limitation, Future direction)
INCLUSION CRITERIA
EXCLUSION CRITERIA
1.Primary discharge diagnosis with the following codes
RSV Bronchiolitis (466.11)
RSV pneumonia (480.1)
RSV not otherwise specified (079.6).
Children > 2 years of age
Children admitted for other conditions and co-incidentally diagnosis of RSV infection
This is one of the few studies done to predict prolonged length of stay in RSV bronchiolitis. Studies have shown that clinicians are significantly influenced in their decision making by pulse oxygen saturation values. Unger et al concluded that oxygen supplementation was a prime determinant of the LOS of infants with bronchiolitis Our study showed these 2 factors to be significantly predictive of LOS. 66% of patients in our study were started on supplemental oxygen without documented oxygen saturation of less than 90%, hence both factors were used in constructing the LOS predictor score. Our analyses showed the score as both sensitive and predictive of prolonged LOS. We suggest that the score may be relevant in deciding the timeframes for LOS, and help in determining patients that might require further review if their predicted LOS is exceeded. The score is simple and does not require significant clinical expertise. It does not determine the need for hospitalization, however once the decision to hospitalize has been made, clinicians and hospital managers may use this information to identify patients with higher risk of longer hospitalizations and pre-emptively optimize inpatient healthcare decisions and cost management strategies.
Limitations: We encountered missing data during chart review as it was a retrospective study and this led to a large decrease in the final charts reviewed. Also this score’s predictive ability may not be generalizable to children > 2 years of age.
In the future, a prospective study evaluating the use of this score as a patient stratification tool and its potential impact on LOS and hospital performance would be necessary to further validate its predictability and value. Further study is required to determine if the score is valid across more recent RSV seasons.
Results
The overall mean LOS was 3.9 days, with a median of 3 days (66.2%) had LOS of 3 or more days. Table 1 summarizes the results of the univariate and multivariate analysis on all investigated predictors of prolonged LOS. The Pearson ᵪ² test for goodness of fit indicated good reliability of the model (p value: 0.794). Four variables had significant association (p value < 0.05) with LOS (Table1). A LOS predictor score was created and validated based on these 4 variables. To construct a simple-to-compute score, regression coefficient of these variables were compared to the smallest coefficient and rounded to the nearest integer. Documented fever, age less than 6 months and oxygen saturation of less than 90% were assigned a weighted value of 1 while supplemental oxygen use had a value of 2. A total predictor score was calculated for each subject within the sample. Subjects had a score for either oxygen saturation or supplemental oxygen. The total score ranged between 0 and 4. The relationship between the score and length of stay was further assessed which showed a positive linear relationship (Fig 1). The model demonstrated good discrimination as assessed by an area under the receiver operating characteristic (ROC) curve of 0.70 (Fig 2). At probability of 0.5, the model was able to identify a considerable number of patients who had prolonged hospital stay at a sensitivity of 83.9%.
References
Hall B. Caroline, Respiratory Syncytial Virus and Parainfluenza Virus . NEJM June 2001; 344:
Mansbach M. Jonathan et al. Prospective, multicenter study of viral etiology and hospital length-of-stay in children with severe bronchiolitis . Arch Pediatr Adolesc Med. Author manuscript; available in PMC Aug 1, 2013.
Unger S and Cunningham S. Effect of Oxygen Supplementation on Length of Stay for Infants Hospitalized with Acute Viral Bronchiolitis. Pediatrics 2008;121;470
Texas Pediatric Society Electronic Poster Contest