title: Hospital volume and patient outcomes in pulmonary embolism.
abstract: BACKGROUND
  In numerous high-risk medical and surgical conditions, a greater volume of patients undergoing treatment in a given setting or facility is associated with better survival. For patients with pulmonary embolism, the relation between the number of patients treated in a hospital (volume) and patient outcome is unknown.
  
  
  METHODS
  We studied discharge records from 186 acute care hospitals in Pennsylvania for a total of 15 531 patients for whom the primary diagnosis was pulmonary embolism. The study outcomes were all-cause mortality in hospital and within 30 days after presentation for pulmonary embolism and the length of hospital stay. We used logistic models to study the association between hospital volume and 30-day mortality and discrete survival models to study the association between in-hospital mortality and time to hospital discharge.
  
  
  RESULTS
  The median annual hospital volume for pulmonary embolism was 20 patients (interquartile range 10-42). Overall in-hospital mortality was 6.0%, whereas 30-day mortality was 9.3%. In multivariable analysis, very-high-volume hospitals (> or = 42 cases per year) had a significantly lower odds of in-hospital death (odds ratio [OR] 0.71, 95% confidence interval [CI] 0.51-0.99) and of 30-day death (OR 0.71, 95% CI 0.54-0.92) than very-low-volume hospitals (< 10 cases per year). Although patients in the very-high-volume hospitals had a slightly longer length of stay than those in the very-low-volume hospitals (mean difference 0.7 days), there was no association between volume and length of stay.
  
  
  CONCLUSIONS
  In hospitals with a high volume of cases, pulmonary embolism was associated with lower short-term mortality. Further research is required to determine the causes of the relation between volume and outcome for patients with pulmonary embolism.
authors.affiliation: Division of Internal Medicine, University of Lausanne, Lausanne, Switzerland. drahomir.aujesky@chuv.ch
authors.forename: Drahomir
authors.initials: D
authors.lastname: Aujesky
authors.forename: Maria K
authors.initials: MK
authors.lastname: Mor
authors.forename: Ming
authors.initials: M
authors.lastname: Geng
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Fine
authors.forename: Bertrand
authors.initials: B
authors.lastname: Renaud
authors.forename: Said A
authors.initials: SA
authors.lastname: Ibrahim
mesh_terms: D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D016208:Databases, Factual; D005260:Female; D017052:Hospital Mortality; D006761:Hospitals / Q000706:statistics & numerical data*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D010414:Pennsylvania; D011655:Pulmonary Embolism / Q000401:mortality*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D017741:Survivors / Q000706:statistics & numerical data