Determination of baseline antibody titre to S. typhi/paratyphi in Ile-Ife, Nigeria.
The aim of the study is to determine the baseline antibody titres to Salmonella typhi/paratyphi in healthy individuals with a view to establishing the significant titre for Widal agglutination test in Ile-Ife, Western Nigeria. Three hundred and ten healthy volunteers were admitted into the study and forty-eight clinically diagnosed and culture positive cases of Enteric fever were used as purposeful controls. Widal test was performed on each serum. Slide agglutination test was first done, then positive samples were further subjected to tube agglutination for quantitative titration. Of the 310 healthy volunteers, 274 (97.2%) had reciprocal antibody titre of < or = 80 to O antigen and 265 (95.0%) had reciprocal antibody titre of < or = 80 to H. antigen of S. typhi. On the other hand, in 48 control cases, 43 (89.6%) had reciprocal antibody titre of > or = 160 to O antigen and 38 (78.2%) had reciprocal titre of > or = 160 to H. antigen. The sensitivity and specificity of the test were 89.9% and 94.2% for O antibody, and 79.2% and 92.3% for H. antibody respectively. The baseline titre to S. typhi/paratyphi for both O & H antibody is 1:80 whilst the significant titre for O & H antibodies is 1:160 and above in Ile-Ife, Nigeria.