Comparative study of agar gel immunodiffusion (AGID) protocols for the diagnosis of equine infectious anemia in Brazil

To evaluate the Equine Infectious Anemia (EIA) agar gel immunodiffusion (AGID) protocols, two different kits commercially available in Brazil were used: an imported kit (kit A) and a domestically produced kit (kit B). Kit A was submitted to the protocols recommended by the World Organization for Animal Health (OIE) and the protocol recommended by the Ministério da Agricultura Pecuária e Abastecimento (MAPA). Kit B, the Brazilian kit, was submitted only to the MAPA-recommended protocol and was used as a reference in this study. A total of 345 equid serum samples, including field samples, serum sets from official laboratories and a weak positive serum control from National Veterinary Services Laboratories (NVSL), were used. Parameters such as the sensitivity of kit A in the two protocols, the detection limit of kits and the occurrence of nonspecific reactions or non-identity were evaluated. When Kit A was used for an AGID procedure performed according to the OIE-recommended protocol, the kit demonstrated good agreement with kit B and 99 % relative sensitivity. However, when kit A was processed according to the MAPA-recommended protocol, it failed to detect 1.16 % of weak positive samples and its relative sensitivity decreased to 96 %. The detection limit of kit A was lower than the detection limit of kit B for weak positive samples in both protocols. The occurrence of nonidentity reactions was higher with kit B than with kit A. The training of veterinarians to ensure the correct execution of the AGID test protocol should be intensified in Brazil.