title: Sampling for collection of central line-day denominators in surveillance of healthcare-associated bloodstream infections.
abstract: OBJECTIVE
  To determine the feasibility of estimating the number of central line-days at a hospital from a sample of months or individual days in a year, for surveillance of healthcare-associated bloodstream infections.
  
  
  METHODS
  We used data reported to the National Nosocomial Infections Surveillance system in the adult and pediatric intensive care unit component for 1995-2003 and data from a sample of hospitals' daily counts of device use for 12 consecutive months. We calculated the percentile error as the central line-associated bloodstream infection percentile based on rates per line-days minus the percentile based on rates per estimated line-days.
  
  
  METHODS
  A total of 247 hospitals were used for sampling whole months and 12 hospitals were used for sampling individual days.
  
  
  RESULTS
  For a 1-month sample of central line-days data, the median percentile error was 3.3 (75th percentile, 7.9; 90th percentile, 15.4). The percentile error decreased with an increase in the number of months sampled. For a 3-month sample, the median percentile error was 1.4 (75th percentile, 4.3; 95th percentile, 8.3). Sampling individual days throughout the year yielded lower percentile errors than sampling an equivalent fraction of whole months. With 1 weekday sampled per week, the median percentile error ranged from 0.65 to 1.40, and the 90th percentile ranged from 2.8 to 5.0. Thus, for 90% of units, collecting data on line-days once a week provides an estimate within +/-5 percentile points of the true line-day rate.
  
  
  CONCLUSIONS
  Sample-based estimates of central line-days can yield results that are acceptable for surveillance of healthcare-associated bloodstream infections.
authors.affiliation: Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333, USA. rmk2@cdc.gov
authors.forename: R M
authors.initials: RM
authors.lastname: Klevens
authors.forename: J I
authors.initials: JI
authors.lastname: Tokars
authors.forename: J
authors.initials: J
authors.lastname: Edwards
authors.forename: T
authors.initials: T
authors.lastname: Horan
mesh_terms: D000328:Adult; D016470:Bacteremia / Q000453:epidemiology* / Q000209:etiology; D017848:Blood-Borne Pathogens; D002405:Catheterization, Central Venous / Q000009:adverse effects*; D002487:Centers for Disease Control and Prevention, U.S.; D002648:Child; D003428:Cross Infection / Q000097:blood / Q000453:epidemiology*; D018563:Disease Notification; D005240:Feasibility Studies; D006801:Humans; D007362:Intensive Care Units / Q000592:standards / Q000706:statistics & numerical data*; D012494:Sampling Studies; D012621:Seasons; D012680:Sensitivity and Specificity; D018571:Sentinel Surveillance; D013995:Time; D014481:United States / Q000453:epidemiology