Usefulness and risks of transtracheal aspiration in the diagnosis of pulmonary infections

OBJECTIVE: To define the diagnostic usefulness and the risks of the transtracheal aspirate in a group of patients studied at the National Institute of Nutrition in Mexico City. DESIGN: It is a retrospective and descriptive analysis of a group of patients in whom a transtracheal aspiration (TTA) was performed due to suspicion of pulmonary infection. The study period was from 1983 to 1987. PATIENTS: On the study period 137 patients were submitted to a TTA; the clinical files of 126 of the cases were considered suitable for analysis. RESULTS: The procedure was performed because of a suspected bacterial pneumonia in 80% of the cases, and to study an interstitial infiltrate or pulmonary nodules in 14% and 6%, respectively. In the cases in which a bacterial pneumonia was suspected, the TTA had a sensitivity of 77% and a specificity of 95% when compared against a group of clinical, radiologic and microbiological data. Sensitivity increased to 84% when the patients who received antibiotics prior to the procedure were excluded. The specificity of the sputum's culture was sensibly less in this same group of patients. The TTA proved to be of value in five of nine pulmonary tuberculosis, two of three pulmonary mycoses and three of seven P. carinii pneumonias. Adverse events were noted in 6.3% of the cases; none of them was fatal, and specific corrective measures were necessary in only two patients. CONCLUSIONS: Our results agree with previous reports related to the usefulness of the TTA on patients with a suspected bacterial pneumonia. Our specificity is higher than that seen by other authors: we believe this is due to the low incidence of chronic respiratory diseases in the patients who attend our hospital. Transtracheal aspirate can be a valuable alternative in the diagnosis of non-bacterial pulmonary infections when the elective procedures cannot be performed. A modification on the technique is proposed to increase its usefulness in patients with interstitial pneumonia.