Invasive Techniques for the Diagnosis of Respiratory Infections

Collection and interpretation of respiratory cytology

Advances in pulmonary cytological sampling have helped establish a more accurate diagnosis and better therapeutic choices for the respiratory patient. Choosing the appropriate test is necessary to maximize the potential diagnostic yield and should be based on the clinical presentation of the patient as well as the minimum database. This article describes several methods of collection of cytological samples for the canine and feline upper and lower respiratory tracts, defines normal respiratory cytology, and discusses normal cytological characterization of various respiratory diseases. Categorization of cytological findings may aid the clinician in narrowing the potential etiologies for the pulmonary disorder. The authors focus on cytological recovery and analysis from transtracheal wash (TTW), bronchial brushing, transthoracic lung aspiration (TTLA), bronchoalveolar lavage (BAL), and open chest biopsy. Indications, complications, and contraindications for each procedure are discussed. Variation in expected findings among BAL, TTW, TTLA, and bronchial brushings are described. Appropriate sampling technique, transport, and processing are also emphasized.

Evaluation of the protected brush catheter and bronchoalveolar lavage in the diagnosis of nosocomial pneumonia

We assess the sensitivity and specificity of the protected brush catheter (PBC) and bronchoalveolar lavage (BAL) in diagnosing nosocomial pneumonia in nonimmunocompromised critically ill patients. Computerized bibliographic literature searches of MEDLINE were performed, and the reference list of each article selected was reviewed. Of 496 citations, there were 19 articles (describing 18 studies) that proved relevant. Study quality was assessed, and descriptive information concerning study populations, interventions, and clinically relevant outcome measurements was extracted. The sensitivity and specificity of PBC were high (pooled estimates, 89.9 and 94.5%, respectively). Criteria for a positive BAL have varied between studies, and sensitivity ranged from 53.3 to 100%, whereas specificity was 98.6%. Most studies did not report whether antibiotics were withheld on the basis of negative test results. In those that did, the incidence of adverse outcomes consequent on withholding antibiotics was low. BAL and PBC, combined with the use of quantitative cultures, appear to increase accuracy in diagnosing pneumonia. The strength of inference is hampered, however, by the absence of a "gold standard" for the diagnosis of pneumonia. Moreover, the generalizability of these findings is limited by the fact that there are so few methodologically sound studies from so few centers. A randomized trial of PBC is needed.

Bronchoalveolar lavage in the evaluation of pulmonary disease in the dog and cat. State of the art

Bronchoalveolar lavage is a diagnostic procedure used to obtain specimens representative of disease processes involving the deep lung. Saline is instilled into an airway in sufficient volumes to bathe the alveoli dependent on that airway. The saline is retrieved by suction along with cellular and acellular material lining the epithelial surfaces of the lung. Cytologic and microbiologic evaluation of the fluid can be used to characterize pulmonary diseases in the dog and cat.

Role of bronchoalveolar lavage in the evaluation of interstitial pneumonitis in recipients of bone marrow transplants

Forty episodes of pneumonitis in 30 recipients of allogeneic bone marrow transplants were investigated by fibreoptic bronchoscopy and bronchoalveolar lavage. A positive diagnosis was made in 32 episodes of pneumonitis (24 patients), giving a diagnostic yield of 80%. In 31 of these the diagnosis was made within 24 hours of bronchoscopy and this enabled the appropriate treatment to be instituted early. Eighteen patients recovered from their primary infection, although two died subsequently of respiratory failure due to postpneumonic lung destruction. Ten patients later developed a second episode of pneumonitis and a diagnosis was made in nine of these. Only three survived a second episode. Bronchoalveolar lavage was well tolerated by all patients and there was no morbidity or mortality that could be directly attributed to the procedure. Bronchoalveolar lavage is a safe and valuable early diagnostic procedure for the investigation of pulmonary complications in patients who have received bone marrow transplants.