Diagnostic tests
The samples were analysed for presence of immunoglobulin
G antibodies to BCV [4] and BRSV [21] by commercially
available indirect enzyme-linked immunosorbent
assays (ELISA; SVANOVA Biotech, Uppsala, Sweden).
The optical density (OD) at 450 nm was corrected by subtraction
of the negative control antigen OD. Cut-off was
set to a corrected OD of 0.20, which is recommended by
the manufacturer for individual samples. At this cut-off,
the sensitivity is estimated to 84.6% for BCV and 94.6%
for BRSV and specificity to 100% for both tests
(SVANOVA manual). A sample was considered test positive
if its corrected OD was >0.20, and test negative otherwise.