Comparison of the Luminex Respiratory Virus Panel Fast Assay with In-House Real-Time PCR for Respiratory Viral Infection Diagnosis

The Luminex xTAG Respiratory Virus Panel (RVP) assay has been shown to offer improved diagnostic sensitivity over traditional viral culture methods and to have a sensitivity comparable to those of individual real-time nucleic acid tests for respiratory viruses. The objective of this retrospective study was to test a new, streamlined version of this assay, the RVP Fast assay, which requires considerably less run time and operator involvement. The study compared the performance of the RVP Fast assay with those of viral culture, a direct fluorescent assay (DFA), and a panel of single and multiplex real-time PCRs in the testing of 286 respiratory specimens submitted to the Edinburgh Specialist Virology Centre for routine diagnosis of viral infection between December 2007 and February 2009. At least one respiratory viral infection was detected in 13.6% of specimens by culture and DFA combined, in 49.7% by real-time PCR, and in 46.2% by the RVP Fast assay. The sensitivity and specificity of the RVP Fast assay compared to the results of real-time PCR as the gold standard were 78.8% and 99.6%, respectively. Real-time PCR-positive specimens missed by the RVP Fast assay generally had low viral loads or were positive for adenovirus. Additionally, a small number of specimens were positive by the RVP Fast assay but were not detected by real-time PCR. For some viral targets, only a small number of positive results were found in our sample set using either method; therefore, the sensitivity of detection of the RVP Fast assay for individual targets could be investigated further with a greater number of virus-positive specimens.Viral infections of the respiratory tract have traditionally been diagnosed in the laboratory by culture of respiratory specimens and direct fluorescent assay (DFA). However, the availability of real-time PCR has allowed us to detect respiratory viruses with greater sensitivity and shorter turnaround times (12). In recent years, a number of new respiratory viruses have been identified, so we must now consider a wider range of viruses in our diagnoses (see, e.g., references 1 and 14). However, the number of fluorophores that can be differentiated in a multiplex real-time PCR assay limits the number of viral targets that can be detected.One solution is to screen each specimen with several different multiplex real-time PCRs to cover a large number of viruses (4). An alternative, the xTAG respiratory virus panel (RVP) assay (Luminex Molecular Diagnostics Inc., Toronto, Canada), is based on suspension microarray technology, which enables the detection of a large number of targets in a single reaction (6, 9). The xTAG RVP assay has been shown to offer results comparable or superior to those of culture/DFA and nucleic acid tests for the diagnosis of respiratory viral infections (7, 10). Recently, the RVP assay has been used successfully for the detection of etiological agents in outbreaks of respiratory illness (3, 15).The latest version of this test, the RVP Fast assay, has a simpler protocol and a shorter turnaround time than the original assay but still detects 19 different viral and subtype targets: influenza A virus (with additional subtyping: H1, H3, and H5), influenza B virus, respiratory syncytial virus A (RSV-A), RSV-B, parainfluenza virus 1 (PIV-1), PIV-2, PIV-3, PIV-4, adenovirus, human metapneumovirus, coronaviruses 229E, NL63, OC43, and HKU1, enterovirus/rhinovirus (EV/RhV), and human bocavirus. Here we compare the performance of the RVP Fast assay with those of culture/DFA and in-house real-time PCR assays, using respiratory specimens collected for routine viral testing.