An epidemiological study to estimate the baseline titres of Widal test in apparently healthy children

Abstract

Background: Enteric fever is one of the common infectious diseases of humans. It is a major health problem in developing countries and its diagnosis on clinical ground is difficult. Diagnosis in developing countries is still mostly done by Widal test. However, the value of the test has been debated. The following study was undertaken to determine the baseline Widal titre (the titre of the antibodies to the O and the H antigens of S. typhi and to the H antigens of S. paratyphi A and B) in normal healthy children.Materials & Methods: A total of 300 children satisfying the eligibility criteria were taken in the study after informed consent from their parents.  ­­­­­A detailed history was taken from each participant with special reference to source of water and method used for purification. Participants were classified into various socio-economic classes as per modified Kuppuswami classification. Widal titres were done with tube agglutination method for all the patients. A Widal antigen kit (antigen suspension of salmonella enterica serotype typhi, paratyphi A and B) was used. Venous blood sample was collected from each participant; left to clot for 15 minutes in the room temperature then sera was separated by using micropipette. The separated sera was properly labeled and stored in -20^C for further study. Results: Most of the study subjects were between 6- 10 years of age with mean age of 7.8 +/- 3.2 years.  More males were observed among study subjects with male to female ratio of 2:1 (67% males vs 33% females).  Over half of the subjects (58.7%) were from middle socio-economic class as per modified kuppuswami classification. About one third were from lower class while only 7% were from upper class. Out of the total 300 subjects, 37% of the subjects were not using any purification method for water and were directly consuming water supplied from municipal sources.   Positive agglutination in Widal test i.e titre ≥ 1:20 was seen in 59% of the healthy subjects.  Positive agglutination in Widal test was observed to be lowest among under-fives as compared to older children (46% vs 62%), but the results were not significant (p-0.06). No significant association was observed between positive agglutination in Widal test and gender (p-0.31). Conclusion: It is clear that Salmonella agglutinins are common among apparently healthy people and as endemicity of typhoid in an area may change over time, more studies should be carried out to determine Salmonella agglutinin titre in apparently healthy populations, so that a better judgment which is based on the prevailing agglutinin titres can be made.