Rapid Diagnosis of Human Influenza Infection from Nasal Smears by Means of Fluorescein-Labeled Antibody.

Abstract

A specific rapid diagnosis of human influenzal infection by staining smears of nasal washings with fluorescein-labeled antibody solution is described. This method was applied to 20 patients during an outbreak of influenza A-prime infections, to 44 cases during an outbreak of influenza B, and to 23 cases of various acute''febrile or respiratory illnesses. Taking a rise of 4-fold or greater in titer of hemagglutination-inhibition (HI) antibody during convalescence, or the recovery of virus from human nasal washings as diagnostic criteria for influenzal infection, the use of fluorescent antibody had a sensitivity of 71% in an influenza A-prime and 38% in an influenza B epidemic. One false positive diagnosis was encountered among 23 non-influenzal infections. The use of labeled antibody on smears of nasal washings is less sensitive than the HI test, but a positive diagnosis could be made on the day the specimens were collected, while the HI test requires a delay of 10 to 14 days for collection of convalescent serum.