MultiCode-PLx system for multiplexed detection of seventeen respiratory viruses

Real-time PCR compared to Binax NOW and cytospin-immunofluorescence for detection of influenza in hospitalized patients

BACKGROUND

Rapid tests have had a significant impact on influenza diagnosis, but more accurate tests are needed for hospitalized patients who test negative by rapid methods.

OBJECTIVE

We sought to determine the increased yield obtained from influenza RT-PCR in hospitalized patients compared to two rapid methods.

STUDY DESIGN

Binax NOW, cytospin-enhanced direct immunofluoroescence (DFA), and influenza A and B multiplex TaqMan RT-PCR were performed on 237 clinical samples.

RESULTS

Binax NOW detected 70 (53.0%), cytospin-DFA detected 127 (96.2%), and TaqMan RT-PCR detected 132 (100%) influenza-positive samples. The difference in sensitivity was significant between RT-PCR and Binax NOW (p<0.0001), but not between RT-PCR and cytospin-DFA (p=0.0736). Two samples testing positive for influenza B by all three methods, tested falsely positive for influenza A by Binax. Eight true positive samples did not become reactive by Binax until 30 min, and thus were counted as negative.

CONCLUSIONS

The accuracy of real-time RT-PCR should greatly improve the diagnosis of influenza in hospitals using simple rapid flu tests, but may have a more modest impact in hospitals with expertise in cytospin-DFA. Further studies are needed to determine the effect of influenza RT-PCR on patient management and costs in hospitalized patients.

Comparison of the Luminex xTAG respiratory viral panel with in-house nucleic acid amplification tests for diagnosis of respiratory virus infections

Detection of respiratory viruses using sensitive real-time nucleic acid amplification tests (NATs) is invaluable for patient and outbreak management. However, the wide range of potential respiratory virus pathogens makes testing using individual real-time NATs expensive and laborious. The objective of this study was to compare the detection of respiratory virus targets using the Luminex xTAG respiratory viral panel (RVP) assay with individual real-time NATs used at the Provincial Laboratory of Public Health, Calgary, Alberta, Canada. The study included 1,530 specimens submitted for diagnosis of respiratory infections from December 2006 to May 2007. Direct-fluorescent-antigen-positive nasopharyngeal samples were excluded from this study. A total of 690 and 643 positives were detected by RVP and in-house NATs, respectively. Kappa correlation between in-house NATs and RVP for all targets ranged from 0.721 to 1.000. The majority of specimens missed by in-house NATs (96.7%) were positive for picornaviruses. Samples missed by RVP were mainly positive for adenovirus (51.7%) or respiratory syncytial virus (27.5%) by in-house NATs and in general had low viral loads. RVP allows for multiplex detection of 20 (and differentiation between 19) respiratory virus targets with considerable time and cost savings compared with alternative NATs. Although this first version of the RVP assay has lower sensitivity than in-house NATs for detection of adenovirus, it has good sensitivity for other targets. The identification of picornaviruses and coronaviruses and concurrent typing of influenza A virus by RVP, which are not currently included in our diagnostic testing algorithm, will improve our diagnosis of respiratory tract infections.

Respiratory viruses other than influenza virus: impact and therapeutic advances

Though several antivirals have been developed and marketed to treat influenza virus infections, the development of antiviral agents with clinical activity against other respiratory viruses has been more problematic. Here we review the epidemiology of respiratory viral infections in immunocompetent and immunocompromised hosts, examine the evidence surrounding the currently available antivirals for respiratory viral infections other than influenza, highlight those that are in the pipeline, and discuss the hurdles for development of such agents.

Evaluation of a multiplexed PCR assay for detection of respiratory viral pathogens in a public health laboratory setting

There are numerous viral and bacterial causes of respiratory disease. To enable rapid and sensitive detection of even the most prevalent causes, there is a need for more-simplified testing systems that enable researchers and clinicians to perform multiplexed molecular diagnostics quickly and easily. To this end, a new multiplexed molecular test called the MultiCode-PLx respiratory virus panel (PLx-RVP) was developed and then implemented in a public health laboratory setting. A total of 687 respiratory samples were analyzed for the presence of 17 viruses that commonly cause respiratory disease. As a comparator, the samples were also tested using a standard testing algorithm that included the use of a real-time influenza virus A and B reverse transcription-PCR test and routine viral culture identification. The standard testing algorithm identified 503 (73%) samples as positive and 184 as negative. Analyzing the same 687 samples, the PLx-RVP assay detected one or more targets in 528 (77%) samples and found 159 samples negative for all targets. There were 25 discordant results between the two systems; 14 samples were positive for viruses not routinely tested for by the Wisconsin State Laboratory of Hygiene, and 13 of these were confirmed by real-time PCR. When the results of the standard testing algorithm were considered "true positives," the PLx-RVP assay showed an overall sensitivity of 99% and an overall specificity of 87%. In total, the PLx-RVP assay detected an additional 40 viral infections, of which 11 were mixed infections.