title: Hospital volume and mortality due to preterm patent ductus arteriosus.
abstract: BACKGROUND
  Preterm patent ductus arteriosus (PDA) requires neonatal intensive care. The relationship between hospital volume and mortality of PDA remains poorly understood.
  
  
  METHODS
  This was a retrospective observational study, using a national inpatient database in Japan. We identified patients who were diagnosed with PDA; exclusion criteria were as follows: (i) other cardiac complications; (ii) mild PDA treated without oral/i.v. indomethacin, surgery, or catheter intervention; (iii) age >1 year at admission; (iv) gestational age ≥32 weeks; (v) death within 3 days of admission; and (vi) transferal to other hospitals. Information was collected using the Japanese Diagnosis Procedure Combination database from July 2010 to March 2013. Hospital volume was defined as the average annual number of neonates with gestational age <32 weeks at each hospital. The outcome measure was in-hospital mortality.
  
  
  RESULTS
  A total of 2437 eligible patients treated at 199 hospitals were included. Low, medium, and high volume were defined as average annual number of preterm infants <34, 34-65, and >65, respectively. There were no significant differences in in-hospital mortality according to hospital volume. In-hospital mortality was identical in patients who received indomethacin alone, surgical or catheter intervention, or both after adjustment for patient background.
  
  
  CONCLUSIONS
  There was no significant relationship between hospital volume and in-hospital mortality due to preterm PDA. Centralization of patients with this condition may not be necessary.
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, University of Tokyo, Tokyo, Japan.
authors.forename: Nobuaki
authors.initials: N
authors.lastname: Michihata
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, University of Tokyo, Tokyo, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Matsui
authors.affiliation: Department of Health Policy and Informatics, Tokyo Medical and Dental University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Kiyohide
authors.initials: K
authors.lastname: Fushimi
authors.affiliation: Department of Clinical Epidemiology and Health Economics, School of Public Health, University of Tokyo, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Yasunaga
mesh_terms: D016208:Databases, Factual; D004374:Ductus Arteriosus, Patent / Q000401:mortality*; D005865:Gestational Age; D017052:Hospital Mortality / Q000639:trends; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D007223:Infant; D007226:Infant Mortality / Q000639:trends; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007234:Infant, Premature; D007235:Infant, Premature, Diseases / Q000401:mortality*; D007564:Japan / Q000453:epidemiology; D012189:Retrospective Studies
keywords: hospital volume; mortality; patent ductus arteriosus; preterm infants