title: Trends in sepsis and infection sources in the United States. A population-based study.
abstract: BACKGROUND
  Stakeholders seek to monitor processes and outcomes of care among patients with sepsis, but use of administrative data for sepsis surveillance is controversial. Prior studies using only principal diagnoses from claims data have shown a trend of rising sepsis incidence with falling infection incidence, implying that administrative data are inaccurate for sepsis surveillance.
  
  
  OBJECTIVE
  Because a sepsis diagnosis often modifies an infection site diagnosis, we sought to investigate trends in sepsis and infection using both principal and secondary diagnoses in administrative data.
  
  
  METHODS
  This was a retrospective cohort study. We used data from the Nationwide Inpatient Sample years 2003 to 2009 to identify age-standardized, population-based trends in sepsis and infection using all available diagnosis codes. Infection sites were defined as bacteremia, pneumonia, urinary tract, skin/soft tissue, and gastrointestinal; codes for septicemia, sepsis, severe sepsis, and septic shock were used to identify "sepsis." We identified patients with infection and mechanical ventilation to estimate incidence of severe sepsis without requiring specific claims for sepsis or acute organ failure.
  
  
  RESULTS
  We identified 53.9 million adult infection hospitalizations during the years 2003 to 2009; average age was 63 years, 61% of patients were women, and 70% reported white race, 14% black, and 11% Hispanic ethnicity. Incidence of hospitalizations with an infection claim increased from 3,147/100,000 U.S. residents in 2003 to 3,480/100,000 in 2009 (11% increase), whereas hospitalizations with sepsis claims increased from 359/100,000 to 535/100,000 residents during the same time frame (49% increase); P = 0.009 between infection and sepsis trends. The proportion of infection hospitalizations with a sepsis claim increased from 7.5% in 2003 to 11.5% in 2009 (54% increase). The incidence of hospitalizations with both an infection and mechanical ventilation claim during 2003 was 173/100,000 as compared with 251/100,000 in 2009 (45% increase); P = 0.76 compared with sepsis trends.
  
  
  CONCLUSIONS
  Sepsis claims are increasing at a greater rate than infection claims but are not inversely related. Trends in sepsis are similar to trends in infection cases requiring mechanical ventilation. Further studies should seek to identify the optimal algorithms to identify sepsis within administrative data and explore potential mechanisms for the increasing incidence of infection and sepsis in the United States.
authors.affiliation: 1 The Pulmonary Center, Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, Boston University School of Medicine, Boston, Massachusetts.
authors.forename: Allan J
authors.initials: AJ
authors.lastname: Walkey
authors.forename: Tara
authors.initials: T
authors.lastname: Lagu
authors.forename: Peter K
authors.initials: PK
authors.lastname: Lindenauer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016470:Bacteremia / Q000453:epidemiology; D015331:Cohort Studies; D003625:Data Collection; D016208:Databases, Factual; D005260:Female; D006760:Hospitalization; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000453:epidemiology*; D012121:Respiration, Artificial / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018805:Sepsis / Q000453:epidemiology*; D012772:Shock, Septic / Q000453:epidemiology; D018461:Soft Tissue Infections / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D014552:Urinary Tract Infections / Q000453:epidemiology*
keywords: health services research; sepsis