problem with ELISA of human gremlin - (Apr/08/2011 )

hello all,
I have undertaken a series of ELISAs of human gremlin and have found out that at the primary antibosy stage (where a R&D biotinylated antibody was used)diluting the antibody with only low salt X1PBS seems to yeild a much more robust assay compared with diluting the primary antibody with PBS-BSA. why is this? any ideas?
Thank you

Non-specific binding - the BSA is there to block sites that the antibody can bind but are not specific to the protein of interest. You should use the BSA-PBS.