Infection Probability Score (IPS): A method to help assess the probability of infection in critically ill patients.
OBJECTIVE
To develop a simple score to help assess the presence or absence of infection in critically ill patients using routinely available variables.


METHODS
Observational study of a prospective cohort of patients divided into a developmental set (n = 353) and a validation set (n = 140).


METHODS
Department of intensive care at an academic tertiary care center.


METHODS
Four hundred and ninety-three adult patients admitted to the intensive care unit for > or =24 hrs.


METHODS
None.


RESULTS
The presence of infection was defined using the Centers for Disease Control definitions. Body temperature, heart rate, respiratory rate, white blood cell count, and C-reactive protein concentrations were measured, and the Sequential Organ Failure Assessment score was calculated throughout the intensive care unit stay. Infection was documented in 92 of the 353 patients (26%) in the developmental set and in 41 of the 140 patients (29%) in the validation set. Univariate logistic regression was used to select significant predictors for infection. Each continuous predictor was transformed in a categorical variable using a robust locally weighted least square regression between infection and the continuous variable of interest. When more than two categories were created, the variable was separated into iso-weighted dummy variables. A multiple logistic regression model predicting infection was calculated with all the variables coded 1 or 0 allowing for relative scoring of the different predictors. The resulting Infection Probability Score consisted of six different variables and ranged from 0 to 26 points (0-2 for temperature, 0-12 for heart rate, 0-1 for respiratory rate, 0-3 for white blood cell count, 0-6 for C-reactive protein, 0-2 for Sequential Organ Failure Assessment score). The best predictors for infection were heart rate and C-reactive protein, whereas respiratory rate was found to have the poorest predictive value. The cutoff value for the Infection Probability Score was 14 points, with a positive predictive value of 53.6% and a negative predictive value of 89.5%. Model performance was very good (Hosmer-Lemeshow statistic, p =.918), and the areas under receiver operating characteristic curves were 0.820 for the developmental set and 0.873 for the validation set.


CONCLUSIONS
The Infection Probability Score is a simple score that can help assess the probability of infection in critically ill patients. The variables used are simple, routinely available, and familiar to clinicians. Patients with a score <14 points have only a 10% risk of infection.
Peres Bota
Daliana
D
Department of Intensive Care, Erasme Hospital, Free University of Brussels, Belgium.
Mélot
Christian
C
Lopes Ferreira
Flavio
F
Vincent
Jean-Louis
JL
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001831:Body Temperature; D002097:C-Reactive Protein / Q000378:metabolism; D003422:Critical Care; D005260:Female; D006801:Humans; D007239:Infections / Q000145:classification / Q000209:etiology / Q000503:physiopathology*; D007362:Intensive Care Units; D007958:Leukocyte Count; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011336:Probability; D011446:Prospective Studies; D018805:Sepsis / Q000503:physiopathology; D012720:Severity of Illness Index
D002097:C-Reactive Protein