Comparing CDC's surveillance definitions and CPIS score in diagnosing ventilator-associated pneumonia: an observational study

Introduction

The National Healthcare Safety Network/Center for Disease Control and Prevention (NHSN/CDC) published in 2013 a new surveillance protocol in order to standardize the ventilator-associated pneumonia (VAP) confirmation criteria and, consequently, to increase the reliability of indicators in different institutions.

Objective

To evaluate the degree of agreement of CDC's new surveillance definitions and clinical criteria, using the CPIS score, in diagnosing VAP.

Methods

From August 2013 to June 2014 all patients on mechanical ventilation for longer than 48 hours in two critical care units in a public and a private general hospital were included in the study. On a daily basis, ventilated patients were evaluated by respiratory physiotherapists using the CPIS score and, independently, by the infection preventionist nurse using CDC's new surveillance definitions. CPIS score = 7 was considered a clinical diagnosis, and, when associated with a semiquantitative culture with 10⁴ colony-forming units, as a definitive diagnosis of VAP.

Results

Eight hundred and one patients were admitted to both ICUs during the study period. One hundred and sixty-eight were on mechanical ventilation for more than 48 hours. Thirty-eight patients were diagnosed with pneumonia using the clinical criteria (13.8/1000 patients/day on ventilation). Eighteen of these patients were diagnosed with infectious conditions associated with mechanical ventilation (IVAC) and 14 of them had a diagnosis of probable VAP (5.23/1000 patients/day on ventilation). Compared with clinical criteria, the CDC's surveillance definitions had sensitivity = 0.37, specificity = 1.0, positive predictive value = 1.0 and negative predictive value = 0.84.

Conclusion

Compared with clinical criteria, using the CPIS score, the CDC's new surveillance definitions had a low sensitivity and may not be appropriate as a surveillance method.