Rapid diagnosis of respiratory syncytial virus infections by immunofluorescence on cell smears from nasopharyngeal secretions.

The efficiency of indirect immunofluorescence for detection of respiratory syncytial (RS) virus antigens in nasopharyngeal secretions was compared with virus isolation on highly sensitive cell culture systems maintained in serum-free media. Twenty out of 22 (91%) culture-positive specimens were correctly identified by indirect immunofluorescence, which gave no false positive results. Since clinical specimens were sometimes unsuitable for immunofluorescence studies, this could explain two false negative results. Thus, this technique proved to be a reliable tool for early diagnosis of RS virus infections; however, in order to avoid false negative results, it should be combined with sensitive cell culture isolation systems.