Comparison of semi-quantitative endotracheal aspirates to quantitative non-bronchoscopic bronchoalveolar lavage in diagnosing ventilator-associated pneumonia.
BACKGROUND
Current strategies for diagnosing ventilator-associated pneumonia (VAP) favor the use of quantitative methods; however, semi-quantitative cultures of endotracheal aspirates are still commonly used.


METHODS
The microbiological results of patients with suspected VAP who had both quantitative cultures with non-bronchoscopic bronchoalveolar lavage (BAL) and semi-quantitative cultures of endotracheal aspirate obtained within 24 hours of each other were retrospectively reviewed and compared, using a quantitative threshold of >or=10(4) colony-forming units/mL as a reference standard.


RESULTS
256 patients with paired cultures were identified. Concordance between endotracheal aspirate (any growth of pathogens) and non-bronchoscopic BAL was complete in 58.2% and completely discordant in 23.8%. The sensitivity and specificity of endotracheal aspirate were 65.4% and 56.1%, which improved to 81.2% and 61.9% when antibiotic management decisions were considered in the analysis. Twenty-six patients had endotracheal aspirate cultures that were falsely negative for pathogens, with 61.5% of these patients demonstrating growth of non-fermenting Gram-negative rods or methicillin-resistant Staphylococcus aureus (MRSA) on non-bronchoscopic BAL. Overall, 45 patients (17.5%) among the entire cohort had false positive endotracheal aspirate cultures, with 19 of these patients (42.2%) demonstrating growth of non-fermenting Gram-negative rods or MRSA.


CONCLUSIONS
Semi-quantitative cultures of endotracheal aspirate are poorly concordant with quantitative cultures obtained via non-bronchoscopic BAL. Although the performance of endotracheal aspirate improves when antibiotic treatment is considered, guiding therapy on the basis of semi-quantitative cultures may still result in failure to identify potentially multiple-drug-resistant pathogens, and would also tend to promote excessive antibiotic usage. Our data support the use of quantitative cultures in diagnosing VAP.
Fujitani
Shigeki
S
Department of Critical Care, University of Pittsburgh, Pittsburgh, PA, USA. shigekifujitani@hotmail.com
Cohen-Melamed
Mark H
MH
Tuttle
Raymond P
RP
Delgado
Edgar
E
Taira
Yasuhiko
Y
Darby
Joseph M
JM
D000368:Aged; D018893:Bronchoalveolar Lavage; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D005188:False Negative Reactions; D005189:False Positive Reactions; D005260:Female; D006090:Gram-Negative Bacteria / Q000302:isolation & purification; D006094:Gram-Positive Bacteria / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D053717:Pneumonia, Ventilator-Associated / Q000175:diagnosis* / Q000382:microbiology; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013396:Suction; D014132:Trachea / Q000382:microbiology*