title: Intercenter variability and time of onset: two crucial issues in the analysis of risk factors for nosocomial sepsis.
abstract: BACKGROUND
  Nosocomial sepsis is one of the most important causes of morbidity and mortality in neonatal intensive care units (NICUs).
  
  
  OBJECTIVE
  To assess the impact of clinical conditions, exposure to invasive procedures and NICU characteristics on late (3 to 10 days) nosocomial sepsis (LNS) and very late (>10 days) nosocomial sepsis (VLNS) and to describe the variability among NICUs.
  
  
  METHODS
  Multicenter prospective study in 21 NICUs including all newborns admitted in a 18-month period, weighing </=1750 g at birth or suffering major illness. Infections were diagnosed according to Centers for Disease Control and Prevention clinical criteria. Kaplan-Meyer curves and Cox models were used to identify major determinants of LNS and VLNS and its intercenter variability.
  
  
  RESULTS
  Of the 2160 neonates admitted to the 21 NICUs, 196 neonates developed a LNS, and 137 developed a VLNS. Some selected neonatal characteristics were independently associated with LNS, but not with VLNS (i.e. respiratory distress syndrome or patent ductus arteriosus), and the opposite was true for other conditions (i.e., necrotizing enterocolitis or high maximum base excess at admission). Exposure to mechanical ventilation and central venous catheter increased the risk of LNS and VLNS. Being admitted to specific NICUs independently increased the risk of both LNS and VLNS.
  
  
  CONCLUSIONS
  To analyze risk factors correctly for hospital-acquired infections in multicenter studies in NICUs, Cox modeling and stratification by time of infection onset should be used, and the existing intercenter variability should be taken into account.
authors.affiliation: INSERM U379, Epidémiologie et Sciences Sociales Appliquées à l'Innovation Médicale, Marseilles, France. Pmcarrieri@aol.com
authors.forename: Maria Patrizia
authors.initials: MP
authors.lastname: Carrieri
authors.forename: Ilaria
authors.initials: I
authors.lastname: Stolfi
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Moro
mesh_terms: D016470:Bacteremia / Q000453:epidemiology* / Q000382:microbiology; D016001:Confidence Intervals; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D007234:Infant, Premature; D007363:Intensive Care Units, Neonatal; D007558:Italy / Q000453:epidemiology; D008297:Male; D015588:Observer Variation; D011336:Probability; D011446:Prospective Studies; D012307:Risk Factors; D012720:Severity of Illness Index; D016019:Survival Analysis; D013997:Time Factors