Bluetongue virus: European Community proficiency test (2007) to evaluate ELISA and RT-PCR detection methods with special reference to pooling of samples

Bluetongue virus European Community national reference laboratories (BTV-EC-NRLs) participated in an inter-laboratory proficiency test in 2007. The aim of the inter-laboratory proficiency test was to determine the ability of laboratories to detect antibodies to a series of BTV serotypes by cELISA and to detect viral RNA in animals infected with the European strain of BTV-8 by RT-PCR. Both serum and EDTA blood sample were diluted in order to determine the sensitivity of the assays. All the cELISAs were 'fit-for purpose' to detect antibodies to the common BTV serotypes circulating in Europe and the real time RT-PCR assays were all capable of detecting BTV-8 RNA albeit with varying sensitivities. There were however inconsistencies in the ability of the gel-based PCR assays to detect BTV RNA. In addition, samples taken on the first day of viraemia and at the peak of viraemia from animals experimentally infected with BTV-8, were diluted to determine if the diluting of samples affected the ability of the Shaw et al. (Shaw, A.E., M., P., Alpar, H.O., Anthony, S., Darpel, K.E., Batten, C.A., Carpenter, S., Jones, H., Oura, C.A.L., King, D.P., Elliott, H., Mellor, P.S., Mertens, P.P.C., 2007. Development and validation of a real-time RT-PCR assay to detect genome bluetongue virus segment 1. Journal of Virological Methods) RT-PCR assay to detect BTV-RNA at these time-points. Results indicated that, if samples were taken at the onset of viraemia, diluting at 1/5 resulted in a reduced ability of the assay to detect BTV RNA in the diluted compared to the neat samples. Diluting samples taken at the peak of viraemia at 1/10 however resulted in no loss in sensitivity.