DIAGNOSTIC-ACCURACY OF PROTECTED SPECIMEN BRUSH AND BRONCHOALVEOLAR LAVAGE IN NOSOCOMIAL PNEUMONIA - IMPACT OF PREVIOUS ANTIMICROBIAL TREATMENTS

Objective: To determine whether the diagnostic accuracy of bronchoscop y samples in patients with suspected ventilator associated pneumonia i s affected by prior antibiotic treatment given for a previous infectio n, and/or by antibiotic treatment recently started to treat suspected ventilator-associated pneumonia.Design: Study of critically ill patien ts. Setting: Intensive care unit in a university hospital. Patients: S ixty three episodes of suspected ventilator-associated pneumonia were prospectively evaluated. Based on prior antibiotic treatment, three gr oups were defined: no antibiotic group (no previous antibiotic treatme nts), n = 12; current antibiotic group (antibiotic treatment initiated >72 hrs earlier), n = 31; and recent antibiotic group (new antibiotic treatment class started within the last 24 hrs), n = 20. Intervention s: Fiberoptic bronchoscopy with quantitative protected specimen brush cultures, bronchoalveolar lavage cultures, and intracellular organism counts of bronchoalveolar lavage cells. Measurements and Main Results: The diagnosis of ventilator associated pneumonia was made in 35 cases , based on histology (n = 2), cavitation (n = 2), blood cultures (n = 4), or outcome under appropriate antibiotic treatment (n = 27). The di scriminative value of the tests, based on the area under the receiver operating characteristic curve, was high (greater than or equal to 0.8 5) in both current antibiotic treatment and recent antibiotic treatmen t patients. Sensitivities for a 5% intracellular organism count of bro nchoalveolar lavage cells, a protected specimen brush culture threshol d of 10(3) colony forming units (cfu)/mL, and a bronchoalveolar lavage culture threshold of 10(5) cfu/mL. were as follows, respectively, in the three groups: 0.71, 0.88, and 0.71 (no antibiotic treatment group) ; 0.5, 0.77, and 0.83 (current antibiotic group); and 0.67, 0.40, and 0.38 (recent antibiotic group). Specificity was consistently greater t han or equal to 0.9, In the recent antibiotic group, protected specime n brush and bronchoalveolar lavage cultures had lower sensitivities (p <.05), and the best threshold values for these two tests were 10(2) c fu/mL and 10(3) cfu/mL, respectively. Conclusions: After recent introd uction of an antibiotic treat ment for suspected ventilator-associated pneumonia, protected specimen brush and bronchoalveolar lavage cultur e thresholds must be decreased to maintain good accuracy. In contrast, current antibiotic treatment prescribed for a prior infectious diseas e does not modify the diagnostic accuracy of protected specimen brush or bronchoalveolar lavage.