Tracheal Aspirate Correlates With Protected Specimen Brush in Long-term Ventilated Patients Who Have Clinical Pneumonia

¹ From the Division of Pulmonary, Critical Care, and Occupational Medicine, Vencor. Tampa Hospital and the University of South Florida College of Medicine, Tampa

Study objective: This study was undertaken to determine whether tracheal aspirate cultures correlate with protected specimen brush (PSB) cultures in the diagnosis of probable ventilator-associated pneumonia (VAP).

Design: Retrospective evaluation of 52 episodes of clinical pneumonia in 38 patients who underwent bronchoscopy and PSB as well as tracheal aspirate cultures.

Setting: The study took place in long-term, acute care hospital associated with a university medical school. This hospital specializes in ventilator-assisted patients.

Patients: The patient population consisted of long-term ventilated patients (average ventilation time was 22 weeks; range, 4 weeks to 3 years) who presented with the clinical diagnosis of VAP (fever, increased white blood cell count, new infiltrate on chest radiograph, and bronchorrhea). No patient had received antibiotics for the preceding 5 days at the time of bronchoscopy or tracheal aspirate culture.

Measurements: The tracheal aspirate and PSB culture and sensitivities results.

Results: Identical organisms were recovered in both the tracheal aspirate and PSB cultures in 36 of 52 episodes of VAP (69 percent). No organism was recovered in either the tracheal aspirate or the PSB in 4 of 52 suspected episodes (8 percent). Positive bacterial cultures in the tracheal aspirate but not the PSB were found in 8 of 52 (15 percent) episodes. In 3 of 52 episodes (6 percent), 1 isolate of pathogenic bacteria was found on PSB and 2 were found on tracheal aspirate cultures. However, all three isolates had the similar antibiotic sensitivities. In the final episode, the PSB culture grew an organism that was not present in the tracheal aspirate culture (2 percent). When comparing the tracheal aspirate with the PSB, the following were calculated: sensitivity =97.7 percent; specificity =50 percent; positive predictive value =91.3 percent; and negative predictive value =80 percent.

Conclusion: Tracheal aspirate cultures correlate with PSB cultures in patients receiving long-term ventilation who have clinical pneumonia, and they can be used to direct initial antibiotic therapy in this group of patients.

Key Words: bacteria • nosocomial pneumonia • pneumonia • protected specimen brush • sputum • tracheal aspirate • ventilation • ventilator-associated pneumonia

Submitted on September 16, 1993
Accepted on February 18, 1994

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