Evaluation of a Commercial Real-Time Reverse Transcription Polymerase Chain Reaction Kit for the Diagnosis of<i>Bovine Respiratory Syncytial Virus</i>Infection

Recently a commercial real-time reverse transcription polymerase chain reaction (RT-PCR) kit has been marketed for the detection of Bovine respiratory syncytial virus (BRSV). However, diagnostic interpretation of the results of this kit requires its comparison to commonly used methods. Therefore, the objective of this study was to evaluate the performance of this kit in comparison with the conventional direct fluorescent antibody test (FAT). Twenty BRSV strains and 14 heterologous bovine viruses were used to check the kit's sensitivity and specificity. The efficiency and detection limit of the kit were determined by testing dilution series of a BRSV strain. The comparison between real-time RT-PCR kit and FAT was performed with 94 clinical samples from calves with clinical signs of respiratory disease including lung tissues (n = 55), transtracheal aspiration samples (n = 20), and nasal swab samples (n = 19). All of the BRSV strains tested were detected by real-time RT-PCR. No cross-reaction was shown with the 14 heterologous bovine viruses. The real-time RT-PCR was 99.3% efficient with a detection limit of 0.1 TCID(50) (50% tissue culture infective dose). The results of real-time RT-PCR and FAT were concordant for 65 of the 94 clinical samples tested. The remaining 29 clinical samples were positive by real-time RT-PCR and negative by FAT, demonstrating the higher sensitivity of real-time RT-PCR. In conclusion, the kit evaluated in this study was sensitive, specific, and had a low threshold of detection. Furthermore, the use of this kit instead of FAT allows an improvement of the sensitivity for the detection of BRSV in clinical samples.