Dot-EIA Typhoid Test Using OMP Salmonella typhi Local Phage Type Antigen

A laboratory study was carried out on 44 sera of typhoid patients (age: 15-45 years, 24 females and 20 males) with positive blood culture for S. typhi, 41 sera non typhoid febrile patients (age: 16-51 years, 17 females & 24 males) with negative blood culture and negative Widal test, 136 sera of healthy persons as normal controls (age: 20-49 years, 95 females & 41 males). The basic principle of the Dot-EIA typhoid test was an indirect Elisa method using nitrocellulose as a solid phase and OMP S. typhi from five locally prevalent phage types as the antigens. Goat anti-human IgM alkaline phosphatase for the Dot-EIA typhoid IgM test and goat antihuman IgG alkaline phosphatase for the Dot-EIA typhoid IgG test were used as conjugates. BCIP/NBT was used as a chromogenic substrate and the results were visible as gray-blue spots on the surface of the nitrocellulose. The Dot-EIA typhoid test could produce results within 3 hours. The result of the Dot-EIA typhoid test showed a good diagnostic value for typhoid fever, a diagnostic sensitivity of 66 % for IgM and 86.4% for IgG and when both were determined (IgM and IgG) the diagnostic sensitivity was 97.7%. The diagnostic specificity was 100% for IgM and 90.24% for IgG and if both were determined (IgM and IgG) the diagnostic specificity was 90.24%. The diagnostic efficiency was 82.35% for IgM and 88.24% for IgG and when both were determined (IgM and IgG) the diagnostic efficiency was 94.12%. The diagnostic positive predictive value was 100% for IgM and 90.48% for IgG and when both were determined (IgM and IgG) the diagnostic positive predictive value was 97.7%. The diagnostic efficiency was 82.35% for IgM and 90.24% for IgG and when both were determined (IgM and IgG) the diagnostic efficiency was 90.24%. The diagnostic positive predictive value was 100% for IgM and 90.48% for IgG and when both were determined (IgM and IgG) the diagnostic positive predictive value was 97.7%. From a practical point of view under field conditions, the performance of the Dot-EIA typhoid IgM and IgG test could be considered as moderately practicable and not very expensive (Rp 5.025,per test). Thus this test could be performed in laboratories up to small hospitals (C type hospitals). Based on these results, it can be concluded that the Dot-EIA typhoid test has a good clinical validity, a moderate practicability and is not very expensive.