title: Emergency readmissions are substantially determined by acute illness severity and chronic debilitating illness: a single centre cohort study.
abstract: BACKGROUND
  The factors influencing hospital readmissions are debated. We assessed whether readmissions could be predicted using routinely collected hospital data.
  
  
  METHODS
  All emergency admissions to a single institution over 12years (2002-2013) were included. The predictor variables, of acute illness severity, Manchester Triage Category, chronic disabling disease and Charlson co-morbidity scores, were studied univariably and entered into a multivariable logistic regression model to predict the bivariate of any readmission or none. A zero truncated Poisson regression model assessed the predictors against the readmission count and incidence rate ratios were calculated. Factors reflecting the clinical load on the emergency department were examined.
  
  
  RESULTS
  66,933 admissions were recorded in 36,271 patients. The readmission rates at 1, 3, 6 and 9years were 29.5%, 38.9%, 42.9% and 44.1%. Early readmissions represented 14.1%. In the multivariable model, an admission in the previous 6months was the strongest predictor of readmission, OR of 5.02 (95% CI: 4.86, 5.18). Acute illness severity - OR of 2.68 (95% CI: 2.33, 3.09) for group VI vs group I, and chronic disabling score - OR of 2.08 (95% CI: 1.87, 2.32) for a score of 4+ vs 0 were significant predictors of readmission in the multivariable model. Both of these predictors demonstrated a linear relationship. Illness severity was the strongest predictor of an early readmission within 4weeks.
  
  
  CONCLUSIONS
  Readmissions increase as a function of time; illness severity, chronic disabling disease score and a recent admission are the strongest predictors of readmission.
authors.affiliation: Department of Internal Medicine, St. James's Hospital, Dublin 8, Ireland.
authors.forename: Richard
authors.initials: R
authors.lastname: Conway
authors.affiliation: Department of Internal Medicine, St. James's Hospital, Dublin 8, Ireland.
authors.forename: Declan
authors.initials: D
authors.lastname: Byrne
authors.affiliation: Department of Internal Medicine, St. James's Hospital, Dublin 8, Ireland.
authors.forename: Deirdre
authors.initials: D
authors.lastname: O'Riordan
authors.affiliation: Department of Internal Medicine, St. James's Hospital, Dublin 8, Ireland. Electronic address: bernardsilke@physicians.ie.
authors.forename: Bernard
authors.initials: B
authors.lastname: Silke
mesh_terms: D000208:Acute Disease; D000328:Adult; D000367:Age Factors; D000368:Aged; D002908:Chronic Disease; D015331:Cohort Studies; D015897:Comorbidity; D016208:Databases, Factual; D004636:Emergency Service, Hospital; D005260:Female; D006801:Humans; D007494:Ireland; D007902:Length of Stay / Q000706:statistics & numerical data*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010359:Patient Readmission / Q000706:statistics & numerical data*; D063728:Secondary Care Centers; D012720:Severity of Illness Index
keywords: Emergency medical admissions; Prediction; Readmission