Detection of antibodies to Salmonella "O" antigens in typhoid fever by counterimmunoelectrophoresis. II. Assessment in patients with typhoid fever and in a healthy population.

Two different population groups were studied. In one, 50 patients with a confirmed diagnosis of typhoid fever. Serum determinations were made for the detection of antibodies to S. typhi somatic antigen using Widal technique, surface fixation test and counterimmunoelectrophoresis (CIE). In the other group, 350 healthy subjects were studied to determine the minimum diagnostic titer by means of CIE. It was possible to establish that a 1:16 titer was suggestive of typhoid fever when CIE techniques were used. Surface fixation test showed the highest sensitivity levels. CIE with sensitivity levels similar to those found in Widal's reaction exceeds the other test because of its standardization and greater reproducibility.