In conclusion, we identified a good agreement between HI tests. However, when horse RBCs were
used, a higher proportion of sera was positive (titre ≥ 4 log2) than using chicken RBCs, especially during the early
response against H5N1 virus. The HRBC-HI might be more responsive in identifying early H5N1 HPAI serological
response and could be a recommended assay for avian influenza sero-surveillance in both wild and domestic birds.