Rapid Detection of Cytomegalovirus Pneumonia from Lung Lavage Cells

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Abstract
Because cytomegalovirus (CMV) is a common cause of fatal pneumonia in the immunocompromised host, a rapid and reliable method to confirm this diagnosis is essential. Bronchoalveolar lavage (BAL) has proved to be a rapid, safe, and sensitive method for the diagnosis of several forms of pneumonia in these patients, but its efficacy for confirming CMV pneumonia remains to be established. In this study, we compared the sensitivity and specificity of conventional viral culture, immunocytochemical staining, and cytological examination performed on cells recovered by BAL for establishing CMV as the cause of pneumonia in 71 BAL specimens from 56 immunocompromised patients. Pneumonia due to CMV was confirmed by stated criteria in 14 of these patients. Virus was isolated by culture in BAL specimens from all patients with CMV pneumonia (sensitivity 100%), but also in 17 specimens from patients who did not have CMV pneumonia (specificity 70%). On cytologic examination, CMV inclusions were found in 3 of the 14 specimens from patients with CMV pneumonia (sensitivity 21%) and also in 1 patient at risk for pneumonia but who did not fulfill the criteria (specificity 98%). Thus, a positive culture and positive cytology virtually confirmed CMV pneumonia, whereas a negative culture excluded it. Immunocytochemistry proved to be particularly useful when the culture was positive and cytology was negative. In this situation, specific labeling of CMV antigen by monoclonal antibody was found in 9 of the 11 patients with CMV pneumonia (sensitivity 82%). Thus, the absence of specific staining in BAL cells tended to exclude CMV as a cause of pneumonia in patients with positive cultures and negative cytologies. Since specific staining was also found in 8 specimens from patients without CMV pneumonia, this approach achieved an unacceptably low specificity of 50%. We recommend that culture and cytology be done on all BAL specimens from patients with suspected CMV pneumonia and that immunocytochemical staining be done primarily when the culture is positive and cytology is negative. In this setting, CMV is an unlikely cause for pneumonia if specific labeling is absent. When the culture is positive and specific labeling is found in the absence of a positive cytology, examination of lung tissue would still be required to establish with confidence that CMV is the cause of pnemonia.