Yahia,and Jazzy, especially E. Histolytica, according to one of the best texts on parasitology, says"
"It has been demonstrated that Cysteine proteinases can degrade both IgA and IgG antibody, which may limit the effectiveness of the host humoral response."
Hence the impossibility of antigen testing turning positive......Very cunning parasite.....
Hence your low IgA; your Brizalian lab was perhaps really correct; you have E. Histolytica! sometimes labs in the 3rd world are better than labs here in the US.