title: [Levels of evidence in the prevention and control of nosocomial infection].
abstract: BACKGROUND
  Sanitary, economic and social importance of nosocomial infections justifies the introduction and development of control and surveillance systems in hospitals. The practice of a rational medicine needs the scientific evidence evaluation of the control measures employed, in terms of efficacy, efficiency and effectivity.
  
  
  METHODS
  Critical appraisal of medical literature with special emphasis in recommendations provided by Centers for Disease Control and Prevention (CDC).
  
  
  RESULTS
  A minimum proportion of prevention and control recommendations provided by Centers for Disease Control and Prevention (CDC) are included in the Category IA (demonstrated evidence in well-designed epidemiological or experimental studies), while sanitary impact (reduction of the nosocomial infection incidence or prevalence) or economic impact (the benefit derived of this nosocomial infection frequency reduction) of numerous interventions keeps being a motive for study and discussion because its evidence level is not demonstrated due to internal or external validity problems.
  
  
  CONCLUSIONS
  An appropriate strategy to be adopted by sanitary professionals in charge of nosocomial infection control is the application of the evidence-based medicine methodology and principles.
authors.affiliation: Servicio de Medicina Preventiva, Hospital Clínico San Carlos, Madrid.
authors.forename: A
authors.initials: A
authors.lastname: Mariano
authors.forename: S
authors.initials: S
authors.lastname: Alonso
authors.forename: D
authors.initials: D
authors.lastname: Gavrila
authors.forename: C
authors.initials: C
authors.lastname: Fernández
authors.forename: P
authors.initials: P
authors.lastname: Sánchez
authors.forename: T
authors.initials: T
authors.lastname: Martín
authors.forename: J
authors.initials: J
authors.lastname: Fereres
mesh_terms: D001424:Bacterial Infections / Q000517:prevention & control; D002487:Centers for Disease Control and Prevention, U.S.; D003428:Cross Infection / Q000191:economics / Q000517:prevention & control* / Q000628:therapy; D004866:Equipment Contamination / Q000517:prevention & control; D005069:Evaluation Studies as Topic; D019317:Evidence-Based Medicine; D006282:Health Personnel; D006739:Hospital Administration; D006761:Hospitals / Q000592:standards; D006801:Humans; D006920:Hygiene / Q000592:standards; D017053:Infection Control / Q000191:economics / Q000379:methods* / Q000458:organization & administration; D009784:Occupational Diseases / Q000517:prevention & control; D010356:Patient Isolation; D011159:Population Surveillance; D017410:Practice Guidelines as Topic; D011785:Quality Assurance, Health Care; D013530:Surgical Wound Infection / Q000517:prevention & control; D014481:United States; D014611:Vaccination