Microbiogical data, but not procalcitonin improve the accuracy of the clinical pulmonary infection score

Abstract

Objective Early and adequate treatment of ventilator-associated pneumonia (VAP) is mandatory to improve the outcome. The aim of this study was to evaluate, in medical ICU patients, the respective and combined impact of the Clinical Pulmonary Infection Score (CPIS), broncho-alveolar lavage (BAL) gram staining, endotracheal aspirate and a biomarker (procalcitonin) for the early diagnosis of VAP. Design Prospective, observational study Setting A medical intensive care unit in a teaching hospital. Patients Over an 8-month period, we prospectively included 57 patients suspected of having 86 episodes of VAP. Intervention The day of suspicion, a BAL as well as alveolar and serum procalcitonin determinations and evaluation of CPIS were performed. Measurements and main results Of 86 BAL performed, 48 were considered positive (cutoff of 10⁴ cfu ml⁻¹). We found no differences in alveolar or serum procalcitonin between VAP and non-VAP patients. Including procalcitonin in the CPIS score did not increase its accuracy (55%) for the diagnosis of VAP. The best tests to predict VAP were modified CPIS (threshold at 6) combined with microbiological data. Indeed, both routinely twice weekly performed endotracheal aspiration at a threshold of 10⁵ cfu ml⁻¹ and BAL gram staining improved pre-test diagnostic accuracy of VAP (77 and 66%, respectively). Conclusion This study showed that alveolar procalcitonin performed by BAL does not help the clinician to identify VAP. It confirmed that serum procalcitonin is not an accurate marker of VAP. In contrast, microbiological resources available at the time of VAP suspicion (BAL gram staining, last available endotracheal aspirate) combined or not with CPIS are helpful in distinguishing VAP diagnosed by BAL from patients with a negative BAL.