ABSTRACT
50 sera from patients with a bacteriological diagnosis of typhoid fever and 325 sera from healthy individuals were studied to quantify antibodies against S. typhi somatic antigen by means of Widal's technique and the enzyme linked inmmunosorbent assay ELISA and by means of the latter, determine the minimum diagnostic titer. Only 2.3 per cent of the healthy population had titers up to 1:300 while sera from patients varied from 1:150 (2 per cent) to 1:2500. A titer was established by ELISA--1:3000 as suggestive of typhoid fever. Widal's agglutination reaction was positive in 1:160 titers in 50 per cent of patients while ELISA technique was positive in 98 per cent of cases (p < 0.001). ELISA technique was more efficient, rapid and sensitive than Widal's test and its utilization is proposed for the clincial laboratory as the method of choice in the serological diagnosis of typhoid fever.
