Estimating attributable mortality due to nosocomial infections acquired in intensive care units.
BACKGROUND
The strength of the association between intensive care unit (ICU)-acquired nosocomial infections (NIs) and mortality might differ according to the methodological approach taken.


OBJECTIVE
To assess the association between ICU-acquired NIs and mortality using the concept of population-attributable fraction (PAF) for patient deaths caused by ICU-acquired NIs in a large cohort of critically ill patients.


METHODS
Eleven ICUs of a French university hospital.


METHODS
We analyzed surveillance data on ICU-acquired NIs collected prospectively during the period from 1995 through 2003. The primary outcome was mortality from ICU-acquired NI stratified by site of infection. A matched-pair, case-control study was performed. Each patient who died before ICU discharge was defined as a case patient, and each patient who survived to ICU discharge was defined as a control patient. The PAF was calculated after adjustment for confounders by use of conditional logistic regression analysis.


RESULTS
Among 8,068 ICU patients, a total of 1,725 deceased patients were successfully matched with 1,725 control patients. The adjusted PAF due to ICU-acquired NI for patients who died before ICU discharge was 14.6% (95% confidence interval [CI], 14.4%-14.8%). Stratified by the type of infection, the PAF was 6.1% (95% CI, 5.7%-6.5%) for pulmonary infection, 3.2% (95% CI, 2.8%-3.5%) for central venous catheter infection, 1.7% (95% CI, 0.9%-2.5%) for bloodstream infection, and 0.0% (95% CI, -0.4% to 0.4%) for urinary tract infection.


CONCLUSIONS
ICU-acquired NI had an important effect on mortality. However, the statistical association between ICU-acquired NI and mortality tended to be less pronounced in findings based on the PAF than in study findings based on estimates of relative risk. Therefore, the choice of methods does matter when the burden of NI needs to be assessed.
Januel
Jean-Marie
JM
Laboratory of Biometry and Evolutionary Biology, CNRS, UMR 5558, Claude Bernard University of Lyon, Lyon, France. jean-marie.januel@chuv.ch
Harbarth
Stephan
S
Allard
Robert
R
Voirin
Nicolas
N
Lepape
Alain
A
Allaouchiche
Bernard
B
Guerin
Claude
C
Lehot
Jean-Jacques
JJ
Robert
Marc-Olivier
MO
Fournier
Gérard
G
Jacques
Didier
D
Chassard
Dominique
D
Gueugniaud
Pierre-Yves
PY
Artru
François
F
Petit
Paul
P
Robert
Dominique
D
Mohammedi
Ismaël
I
Girard
Raphaëlle
R
Cêtre
Jean-Charles
JC
Nicolle
Marie-Christine
MC
Grando
Jacqueline
J
Fabry
Jacques
J
Vanhems
Philippe
P
D016022:Case-Control Studies; D002423:Cause of Death; D016638:Critical Illness; D003428:Cross Infection / Q000453:epidemiology / Q000401:mortality*; D005602:France; D017052:Hospital Mortality / Q000639:trends*; D006785:Hospitals, University; D006801:Humans; D015994:Incidence; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007902:Length of Stay; D011159:Population Surveillance / Q000379:methods; D012306:Risk