Comparison of nasal brush and nasopharyngeal aspirate techniques in obtaining specimens for detection of respiratory syncytial viral antigen by immunofluorescence

Diagnosis of respiratory syncytial virus by antigen detection is dependent on obtaining adequate respiratory epithelial cells. Two specimen collection methods, nasopharyngeal aspiration (NPA) and nasal brushing (NB), were compared. Thirty-two pediatric patients with presumed viral pneumonia or bronchiolitis (34 episodes) had both NPA and NB performed. Of 34 specimens 15 were culture-positive for respiratory syncytial virus. Of these 12 NPA samples and 10 NB samples had viral inclusions by immunofluorescent antibody staining (IFA). Of culture-negative samples, 1 of 17 NB was positive by IFA. One specimen obtained by NB had too few cells to read by the IFA method. Sensitivity and specificity were 80 and 100% for NPA and 67 and 94% for NB. Total respiratory cells and IFA-positive cells (classified as few, moderate, or many) were greater with NPA; however, NB was also an effective procedure and was better tolerated by children, less expensive and easier to perform.