A comparison of direct immunofluorescence, shell vial culture, and conventional cell culture for the rapid detection of influenza A and B.

Direct immunofluorescence (FA) and shell vial contrifugation cultures (SVCs) were compared with conventional tube cultures for the rapid detection of influenza A and B by using a commercial antibody. Of the 439 specimens tested, 82 were positive by conventional culture (CC). The direct smear prepared from pelleted cells or direct swab material exhibited positive fluorescence in only seven (8.5%) of these cases, whereas the SVC was positive in 30 (37%). The SVC method detected 12 additional positive isolates that were not recovered in CC. The mean time to isolation in CC was 3.6 days for influenza A and 4.3 days for influenza B. The use of SVC provided more rapid results (36-48 hr). The FA method, although more rapid, may be of limited sensitivity and difficult to interpret depending on the quality of the specimen. The results indicate that SVC complements conventional culture in the rapid detection of influenza and can detect infections that may be missed in conventional tubes, but should not be used to the exclusion of conventional culture.