Comparison of Directigen FLU-A with viral isolation and direct immunofluorescence for the rapid detection and identification of influenza A virus

Abstract

Directigen FLU-A, an enzyme immunoassay membrane test, was compared prospectively to isolation in cell culture and direct immunofluorescence (IF) for the detection of influenza A virus. One hundred ninety specimens were evaluated by Directigen FLU-A and cell culture; 184 of these specimens were also tested by direct IF. The sensitivity of Directigen FLU-A compared to isolation in cell culture and direct IF was 100%. The specificities of Directigen FLU-A compared to isolation and direct IF were identical, 91.6%. Fourteen specimens that were positive by Directigen FLU-A did not yield virus in culture; two of the specimens, however, were positive by direct IF, and four other specimens were not specimens of choice for the test. A positive Directigen result had positive predictive values of 62.6 and 75.0% compared to isolation and direct IF, respectively; a positive Directigen result with an intensity reading of 2+ or greater, however, had positive predictive values of 85 and 100% compared to isolation and direct IF, respectively. In all comparisons, the negative predictive value was 100%. There was no evidence that cross-reactivity occurred with non-influenza A antigens. Directigen FLU-A should serve as a convenient screening test for influenza A and as a rapid test supported by isolation in cell culture during an influenza outbreak.

Evaluation of the Directigen FluA+B Test for Rapid Diagnosis of Influenza Virus Type A and B Infections

“…The previous version of this assay, Directigen Flu-A, used for detection of influenza virus type A alone, was reported to give similar sensitivity with nasopharyngeal washes (18). In experimental human infections, nasopharyngeal washes contained approximately 1.8 log 10 and 3 log 10 more virus than nasopharyngeal swabs and throat swabs, respectively.…”

“…Directigen Flu-A (Becton Dickinson) has been widely used for the rapid diagnosis of influenza virus type A and has been shown to be sensitive and specific (16,18). In this paper, we evaluate a new version of this test, Directigen FluAϩB, that detects influenza type A and B viruses and discriminates between them.…”

Design and performance testing of quantitative real time PCR assays for influenza A and B viral load measurement

“…The success of assays such as the CE-ELISA is also dependent on the availability of monoclonal antibodies of high sensitivity and specificity to detect viral nucleoprotein. There is evidence to suggest that the results of diagnostic tests dependent upon the detection of nucleoprotein by an enzyme conjugated monoclonal antibody, such as Directigen TM FLU-A test (Beckton Dickinson, Cockeysville, Maryland, US), are affected by freezing and thawing of specimens prior to testing (Waner et al, 1991). The nucleic acid based real time PCR assays were not affected by up to five sample freeze-thaw events, suggesting that even though influenza is an RNA virus, methods based upon the amplification of short segments of viral RNA are robust.…”

Comparison of the BD Directigen Flu A+B Kit and the Abbott TestPack RSV with a multiplex RT-PCR ELISA for rapid detection of influenza viruses and respiratory syncytial virus

“…The observed low sensitivities for influenza A and B with the DirectigenFluA+Bassay(29.3%and10.0%,respectively) are in contrast to those of Chan et al [12], who reported a sensitivity of 96% for influenza A and 87.5% for influenza B, but are more in agreement with those of Cazacu et al [13], who reported an overall sensitivity of 43.83% for influenza A and B detected with the same test. Published singleprimer RT-PCRs for influenza A have sensitivities of 92-95% [14,15], which are comparable to those obtained with cell culture combined with immunofluorescence [15], while sensitivities obtained with rapid diagnostic immunoassays for influenza A vary from 75% [16,17] to 100% [8,16,18]. It is accepted widely that PCR techniques are superior to EIAs with regard to sensitivity and specificity [18].…”