EVALUATION OF PROFLU+ FOR REAL-TIME AMPLIFICATION AND DETECTION OF INFLUENZA AND RESPIRATORY SYNCYTIAL VIRUSES

Most acute respiratory tract infections (ARTI) are caused by influenza viruses A and B (Flu A and B) and respiratory syncytial virus (RSV). Rapid diagnosis of these viral pathogens is important for infection control and therapeutic purposes. Respiratory viruses have been classically identified by viral culture, which can take up to 14 days. Rapid immunoenzymatic assays are commercially available; however, the sensitivity is lower than that of viral culture. Previously we compared the performance of three manufacturer’s ASRs for real-time molecular amplification of these viruses: bioMerieux NucliSens EasyQ RSV A+B Primer-Probe Mix; Cepheid Respiratory Syncytial Virus Primer and Probe Set and Cepheid Influenza Virus A/B Primer and Probe Set; and Prodesse Pro-Flu1. In addition, in-house developed NASBA assays for the detection of Flu A and B were also tested. The overall sensitivities for the NASBA and Cepheid ASR were comparable where as the sensitivity Prodesse ASR and culture were considerably lacking. Recently Prodesse has introduced an FDA approved kit, ProFlu+ for the multiplex amplification of all 3 analytes. This kit has been described as a modified version of their previous ASR with enhanced sensitivity. However, a comparison to other very sensitive amplification assays is yet to be reported. In a retrospective analysis of 60 respiratory specimens sent to the laboratory for viral antigen and culture, all specimens were tested for RSV, Flu A and Flu B with the ProFlu+ kit and by NASBA. Cases were considered true positive if positive by two or more assays, including culture. Of the 60 specimens, 17 were positive for RSV, 22 were positive for Flu A and 8 were positive for Flu B. Virus was detected by culture, ProFlu+ or bioMerieux’s ASR in all 17 RSV positive samples and in the 8 Flu B positive samples, whereas Flu A was detected by culture in only 16 of the 22 positive samples. Both the molecular tests detected Flu A in all 22 samples. Of the 13 samples considered to be true negative, 1 was RSV antigen positive and 1 was Flu A positive with the ProFlu+ kit. Based on these findings the overall sensitivity of the ProFlu+ and NASBA was 100% for all viruses, whereas traditional test methods were only 78%. In addition, the modification made to the ProFlu+ greatly improved the sensitivity as compared to Prodesse’s previous ASR.