title: [Method to calculate the additional hospital stay in patients with cross infection].
abstract: OBJECTIVE
  To calculate additional hospital stay due to specific cross infection.
  
  
  METHODS
  Cases and controls study; matched by age +/- 2 years, sex, specialty in which were taken care, diagnosis, surgical procedure and hospitalization stay, between July 2005-June 2006.
  
  
  METHODS
  t test, chi(2) to calculate death risk, Kaplan-Meier analysis to calculate survival, Hosmer-Lemeshow test to know the contribution of cross infection for additional hospital stay due to cross infection (AHSDCI).
  
  
  RESULTS
  We identified 851 patients with 1347 cross infection in 16 528 discharges. We could match 677. The cases stayed 25.42 days and the controls 13.29 (p < 0.01). The death risk for the cases was 5.8 (CI 95 % = 3.7-8.6, p < 0.01), four weeks survival 55.3 % for cases and 79.2 % for the controls. The AHSDCI for pneumonia was 10.39 days, urinary-tract-infection 6.28, bacteremia 8.92, vascular-catheter-related infection 3.31, surgical site infections 7.42, and skin and soft-tissue-infection 3.31 (p < 0.05).
  
  
  CONCLUSIONS
  We used a multivariate model fitted to patient's gravity and complexity to extract the proportion days of AHSDCI of each cross infection.
authors.affiliation: División de Medicina Preventiva y Epidemiología Hospitalaria, Hospital de Especialidades, Centro Médico Nacional La Raza, Instituto Mexicano del Seguro Social, Distrito Federal, México. ulises.angeles@imss.gob.mx
authors.forename: Ulises
authors.initials: U
authors.lastname: Angeles-Garay
authors.forename: Yesenia
authors.initials: Y
authors.lastname: Velázquez-Chávez
authors.forename: Fernando
authors.initials: F
authors.lastname: Molinar-Ramos
authors.forename: Verónica E
authors.initials: VE
authors.lastname: Anaya-Flores
authors.forename: Samuel E
authors.initials: SE
authors.lastname: Uribe-Márquez
mesh_terms: D016022:Case-Control Studies; D003428:Cross Infection / Q000628:therapy; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged