ELISA
Standard wells and blank wells were set in accordance with the protocol of the Bioswamp ELISA kit. Serum (40 μl) was added to each sample well, and 10 μl biotinylated antibody and 50 μl HRP-conjugated reagent were added to each well except the blank well. After incubating for 30 min at 37°C, washing buffer was added to every well and samples were rested for 30 s five times. Then, chromogen solution was added to each well and samples were incubated for 10 min at 37°C. Lastly, stop solution was added to terminate the reaction and the optical density (OD) at 450 nm was measured within 15 min.