Evaluation of the QuickLab RSV Test, a New Rapid Lateral-Flow Immunoassay for Detection of Respiratory Syncytial Virus Antigen

Abstract

Rapid respiratory syncytial virus (RSV) diagnosis is vital to the prevention of nosocomial RSV infections. We evaluated a new rapid lateral-flow RSV immunoassay, the QuickLab RSV test, that requires use of only one reagent. We compared QuickLab to the Directigen RSV (DIR) assay, which requires six reagents, and direct fluorescent antibody (DFA) testing. DFA results were considered the "gold standard." For 133 nasopharyngeal aspirates tested, DFA results were 77 (57.8%) positive, 47 (35.3%) negative, and 9 (6.8%) indeterminate. The sensitivities, specificities, positive predictive values, and negative predictive values of QuickLab and DIR tests were 93.3% (70 of 75) and 80.8% (59 of 73), 95.6% (43 of 45) and 100.0% (46 of 46), 97.2% (70 of 72) and 100.0% (59 of 59), and 89.6% (43 of 48) and 76.7% (46 of 60), respectively. QuickLab was significantly (P ‫؍‬ 0.02) more sensitive than DIR; the difference in specificities was not significant. DFA was more sensitive than DIR (P < 0.001) but not more sensitive than QuickLab (P ‫؍‬ 0.45). The results of DIR testing were initially uninterpretable and required retesting with 15% of the specimens compared to 3% of QL results (P < 0.001). We conclude that the QuickLab RSV test has sensitivity similar to that of the DFA assay and better than that of the DIR assay. QuickLab testing is also simpler to perform and interpret than both DFA and DIR testing.Rapid diagnosis of respiratory syncytial virus (RSV) infection in infants and children requiring hospital admission can help prevent nosocomial RSV transmission (5, 6, 7), since RSV-infected patients can be either assigned to private rooms or cohorted with other children infected with the same virus. Infection control strategies that include rapid diagnostic tests have been shown to be cost effective for this reason (6). Rapid RSV diagnosis may also be important for therapeutic reasons, although the benefits of ribavirin treatment are unclear (1).The rapid tests that are now widely used have shown moderately good sensitivity and specificity in studies published primarily in the early 1990s (3,4,8,9,11). However, these tests generally require multiple processing steps and the addition of reagents. Thus, although total individual test time is short, the hands-on involvement for the operator over the test interval is high. Simpler tests might be amenable to point-of-care use in settings such as emergency rooms. Another potential disadvantage of some existing solid-phase membrane-bound immunoassays is that test results must be read in the same well in which a specimen is absorbed. Substances in the specimen that interfere with absorption may thus make test results difficult to interpret.The QuickLab RSV (QL) test (Integrated Biotechnology Corp.; test now sold as the Clearview RSV test [Wampole Laboratories]) is a recently approved immunoassay that may overcome these disadvantages. First, it requires the addition of only one reagent to the specimen prior to the addition of a sample to a test strip. Secondly, this test is an example of...

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