Preparation of nasopharyngeal secretions for immunofluorescence by one-step centrifugation through Percoll

A simple method was developed for separation of cells from nasopharyngeal secretion for the diagnosis of respiratory virus infections by immunofluorescence microscopy. The diluted specimen, containing dithiothreitol to break up the mucus, was centrifuged once through a cushion of 20% Percoll (colloidal silica, a density gradient medium), which permitted sedimentation of cells through the cushion, but retained mucus on top of it. The pelleted cells were resuspended, and microscope slides were then prepared by standard techniques. The Percoll centrifugation method was also applicable for sputum and bronchoaveolar lavation specimens. Immunofluorescent antibody staining of nasopharyngeal secretions prepared by the described method was more sensitive than enzyme immunoassay for the detection of respiratory syncytial virus.