Research

Ventilator associated pneumonia: comparison between quantitative and qualitative cultures of tracheal aspirates

Luis Fernando Aranha Camargo¹ , Fernando Vinícius De Marco², Carmen Sílvia Valente Barbas¹ , Cristiane Hoelz¹ , Marco Aurélio Scarpinella Bueno¹ , Milton Rodrigues Jr¹ , Verônica Moreira Amado¹ , Raquel Caserta³ , Marinês Dalla Valle Martino⁴ , Jacyr Pasternak⁴ and Elias Knobel⁵

¹Assistant Physican, Intensive Care Unit, Hospital Israelita Albert Einstein, São Paulo, Brasil

²Postgraduate Fellow, Intensive Care Unit, Hospital Israelita Albert Einstein, São Paulo, Brasil

³Respiratory Therapist, Intensive Care Unit, Hospital Israelita Albert Einstein, São Paulo, Brasil

⁴Microbiology Laboratory, Intensive Care Unit, Hospital Israelita Albert Einstein, São Paulo, Brasil

⁵Head, Intensive Care Unit, Hospital Israelita Albert Einstein, São Paulo, Brasil

author email corresponding author email

Critical Care 2004, 8:R422-R430doi:10.1186/cc2965

Published:	14 October 2004

See related commentary http://ccforum.com/content/8/6/425

Abstract

Introduction

Deferred or inappropriate antibiotic treatment in ventilator-associated pneumonia (VAP) is associated with increased mortality, and clinical and radiological criteria are frequently employed to establish an early diagnosis. Culture results are used to confirm the clinical diagnosis and to adjust or sometimes withdraw antibiotic treatment. Tracheal aspirates have been shown to be useful for these purposes. Nonetheless, little is known about the usefulness of quantitative findings in tracheal secretions for diagnosing VAP.

Methods

To determine the value of quantification of bacterial colonies in tracheal aspirates for diagnosing VAP, we conducted a prospective follow-up study of 106 intensive care unit patients who were under ventilatory support. In total, the findings from 219 sequential weekly evaluations for VAP were examined. Clinical and radiological parameters were recorded and evaluated by three independent experts; a diagnosis of VAP required the agreement of at least two of the three experts. At the same time, cultures of tracheal aspirates were analyzed qualitatively and quantitatively (10⁵ colony-forming units [cfu]/ml and 10⁶ cfu/ml)

Results

Quantitative cultures of tracheal aspirates (10⁵ cfu/ml and 10⁶ cfu/ml) exhibited increased specificity (48% and 78%, respectively) over qualitative cultures (23%), but decreased sensitivity (26% and 65%, respectively) as compared with the qualitative findings (81%). Quantification did not improve the ability to predict a diagnosis of VAP.

Conclusion

Quantitative cultures of tracheal aspirates in selected critically ill patients have decreased sensitivity when compared with qualitative results, and they should not replace the latter to confirm a clinical diagnosis of VAP or to adjust antimicrobial therapy.