Document Detail

Very low birth weight hospital volume and mortality: an instrumental variables approach.
MedLine Citation:
PMID:  22437621     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Previous studies of very low birth weight (VLBW) hospital volume effects on in-hospital mortality have used standard risk-adjusted models that only account for observable confounders but not for self-selection bias due to unobservable confounders.
OBJECTIVE: To assess the effects of hospital volume of VLBW infants on in-hospital mortality while explicitly accounting for unobservable confounders and self-selection bias using an instrumental variables (IV) model.
METHODS: The sample includes 4553 VLBW infants born in 63 hospitals in 2000-2004 in New Jersey. We use IV analysis with the differences between the patient's distances to the nearest low (<50 VLBW infants annually), moderate (51-100 infants annually), and high (>100 VLBW infants annually)-volume hospitals as instruments. We evaluate several volume measures and adjusted for observable infant and hospital characteristics.
RESULTS: We find beneficial volume effects on survival that are significantly underestimated in classic risk-adjusted models, under which low and moderate volumes compared with high volumes increase mortality odds by 1.8 and 1.88 times, respectively (risk ratios of 1.4 and 1.5, respectively). However, using the IV approach, we find that low and moderate volumes increase mortality odds by 5.42 and 3.51 times, respectively (risk ratios of 2.76 and 2.21, respectively). These findings suggest unobservable confounders that increase the selection of infants at a greater mortality risk into higher-volume hospitals.
CONCLUSIONS: Accounting for unobserved self-selection bias reveals large survival benefits from delivering and treating VLBW infants at high-volume hospitals. This supports policies regionalizing the delivery and care for pregnancies at risk for VLBW at high-volume hospitals.
George L Wehby; Fred Ullrich; Yang Xie
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Medical care     Volume:  50     ISSN:  1537-1948     ISO Abbreviation:  Med Care     Publication Date:  2012 Aug 
Date Detail:
Created Date:  2012-07-11     Completed Date:  2012-09-26     Revised Date:  2014-09-21    
Medline Journal Info:
Nlm Unique ID:  0230027     Medline TA:  Med Care     Country:  United States    
Other Details:
Languages:  eng     Pagination:  714-21     Citation Subset:  IM    
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MeSH Terms
Hospital Administration / statistics & numerical data*
Hospital Mortality*
Infant Mortality / trends*
Infant, Newborn
Infant, Very Low Birth Weight*
Intensive Care Units, Neonatal / statistics & numerical data
Risk Adjustment
Selection Bias
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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