title: Using clinical databases to evaluate healthcare interventions.
abstract: OBJECTIVE
  The aim of this study was to test the feasibility of conducting rigorous, nonrandomized studies (NRSs) of healthcare interventions using existing clinical databases in terms of the following: recruiting a large representative sample of hospitals, identifying eligible cases, matching cases to controls to achieve similar baseline characteristics, making meaningful comparisons of outcomes, and carrying out subgroup analyses.
  
  
  METHODS
  Data were extracted from the Intensive Care National Audit & Research Centre's Case Mix Programme Database to investigate the impact of management with a pulmonary artery catheter (PAC) in intensive care unit (ICU) patients. Participating ICUs were invited to collect additional data for the analysis. Patients managed with a PAC were matched to control patients on their propensity score. Hospital mortality was then compared between the two groups.
  
  
  RESULTS
  Of 117 eligible ICUs, 68 (58 percent) agreed to participate, of which 57 (84 percent) collected additional data. Although a slightly higher proportion of larger ICUs in university hospitals participated, the patient case-mix was similar to that in nonparticipating ICUs. Almost all patients managed with a PAC (98 percent) were successfully matched to patients managed without a PAC. The two groups were similar for baseline characteristics. However, hospital mortality was worse for PAC patients than for non-PAC patients (odds ratio, 1.28; 95 percent confidence interval, 1.06-1.55). Subgroup analysis suggested that the impact of management with a PAC was modified by severity of illness.
  
  
  CONCLUSIONS
  Rigorous NRSs are feasible if they are based on data from high-quality clinical databases. However, the reliability of estimated treatment effects from such studies requires further investigation.
authors.affiliation: Epidemiology & Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London WC1E 7HT, UK. sheila.harvey@lshtm.ac.uk
authors.forename: Sheila
authors.initials: S
authors.lastname: Harvey
authors.forename: Kathy
authors.initials: K
authors.lastname: Rowan
authors.forename: David
authors.initials: D
authors.lastname: Harrison
authors.forename: Nick
authors.initials: N
authors.lastname: Black
mesh_terms: D000368:Aged; D002407:Catheterization, Swan-Ganz / Q000401:mortality / Q000706:statistics & numerical data*; D015331:Cohort Studies; D016208:Databases, Factual / Q000706:statistics & numerical data*; D005260:Female; D006739:Hospital Administration / Q000706:statistics & numerical data*; D017052:Hospital Mortality; D006801:Humans; D007256:Information Systems / Q000706:statistics & numerical data*; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D020379:Risk Adjustment