A prospective observational cohort study was undertaken with two endpoints: (1) to compare the time cut-off of 48h and the carrier state criterion for classifying lower airway @entity281 in adult and paediatric long-term ventilated @entity1 , and (2) to evaluate the potential of optimized time cut-offs for characterizing imported and ICU-acquired lower airway @entity281 . All @entity1 admitted to the general and paediatric intensive care units and expected to require mechanical ventilation for a period > or = 3 days were enrolled. Surveillance cultures of throat and rectum were obtained on admission and thereafter twice weekly to distinguish micro-organisms that were imported into the unit from those acquired during the stay on the unit. A total of 130 adults and 400 @entity1 were studied. In the adult population, 70% of lower airway @entity281 were classified as ICU-acquired by the 48 h cut-off and 48% by the criterion of carriage; on the paediatric ICU the percentages were 65% and 20%, respectively. To separate imported from ICU-acquired @entity281 , eight days was optimal in the adult population and 10 days in the paediatric population. Sensitivity, specificity, positive predictive value and negative predictive value for a time cut-off of eight days for adults were 86, 77, 80, 83%, respectively, and using 10 days for @entity1 were 87, 62, 90, 56%, respectively. The use of the 48 h cut-off rule classifies @entity1 as having @entity55 , when in fact the @entity281 are commonly caused by microorganisms carried in by the @entity1 . In contrast, using the carriage method, the proportion of @entity358 due to nosocomial bacteria was relatively small and was a late phenomenon. Although in prolonging the time cut-off the difference between the two types of classification was shorter, time cut-offs were still found to be unreliable for distinguishing imported from unit-acquired lower airway @entity281 .

Most XXXX are not due to nosocomial bacteria in ventilated @entity1 . Evaluation of the accuracy of the 48 h time cut-off using carriage as the gold standard.

@entity1 :: ('9606', 'Species') :: ['children', 'patients'] @entity281 :: ('MESH:D007239', 'Disease') :: ['infections'] @entity358 :: ('MESH:D008171', 'Disease') :: ['lung infections'] @entity55 :: ('MESH:D011014', 'Disease') :: ['nosocomial pneumonia']
@entity55 :: (MESH:D011014,Disease) :: ['nosocomial pneumonias']
