Diagnostic accuracy of transtracheal aspiration bacteriologic studies.

The diagnostic accuracy of transtracheal aspiration bacteriologic studies was examined in 488 patients. Twenty-three patients had bacteremic pneumonia, and in each instance the blood culture isolate was also recovered from the transtracheal aspirate. Clinical correlations in 119 patients with negative cultures of transtracheal aspirate indicated that 71 had an alternative diagnosis to explain an abnormal chest radiograph, and 44 appeared to have a bacterial infection but had received antimicrobial drugs before specimen collection. According to clinical parameters and final diagnosis, the incidence of false-negative cultures was 1 per cent among patients sampled before administration of antimicrobial drugs, and the incidence of false-positive cultures was 21 per cent.