Enzyme linked immunoassay for early diagnosis of Typhoid fever using Salmonella typhi outer membrane protein

An indirect enzyme-linked immunosorbent assay (ELISA) was used to detect immunoglobulin M antibodies against outer membrane protein (OMPs) from Salmonella typhi as the antigen. Acute phase, first week, sera from adult patients with culture confirmed typhoid fever, sera from culture negative suspected typhoid fever and sera from healthy blood donors were tested. Sera from the three groups gave a mean absorbance reading at 492 nm, of 1.21 + 0.59, 0.15 ± 0.13 and 0.11 ± 0.08, respectively. The sensitivity, specificity, positive and negative predictive values were 81.5%, 100%, 100% and 90.2%, respectively. The cut off value obtained was 0.35 and in which the ELISA test of typhoid fever patients (Group 1) showed the mean absorbance reading approximately 3.5 times higher.