LOW-SENSITIVITY OF COUNTERCURRENT IMMUNOELECTROPHORESIS FOR SERODIAGNOSIS OF TYPHOID-FEVER

Counter-current immuno-electrophoresis was evaluated as a diagnostic t est for the serodiagnosis of typhoid fever with somatic (O), flagellar (H) and capsular polysaccharide (Vi) antigens of Salmonella typhi on the sera of patients who were blood culture positive (confirmed typhoi d cases) or had high Widal agglutination titres, greater than or equal to 320, (presumptive typhoid cases). Of the 37 sera from confirmed ca ses, 30% showed positivity with O antigen, 24% with H antigens and 51% with Vi antigen. In patients with a presumptive diagnosis, 45% were p ositive for O antibody, 27% for flagellar antibody and 52% for Vi anti body. When all three antigens were combined the reactivity to any of t he antigens was found to be 59% in confirmed typhoid cases, 79% in pre sumptive typhoid cases and 93% in patients who were simultaneously pos itive by blood culture and Widal agglutination. However, none of the s era from 45 controls gave a positive precipitation reaction with any o f the antigens. It is concluded that countercurrent immuno-electrophor esis is a rapid test with low sensitivity and high specificity with Vi antigen, a panel of antigens being most effective, and is, therefore, recommended for rapid diagnosis of typhoid fever.