Enteric fever is a major endemic health problem among children in India. For these reasons, laboratory diagnosis of enteric fever relies heavily on serological tests such as the Widal test.

In endemic region, interpretation of Widal test depends on knowledge of the baseline titres among healthy population.

In study conducted by Kulkarni et al in 1994, more than a decade ago in Davangere, 50 normal children had anti O titre of <1:20, 1:20, 1:40, 1:80, in 52%, 34%, 10%, 4% respectively and anti H titre of <1:20, 1:20 in 90%, 10% respectively.

The level of titres detectable in normal population of different areas vary considerably. This variation depends on the degree to which the typhoid is endemic in each area, a fact which may change over time. It has been a decade ago since the Widal titres were assessed in healthy children in this part, we found it necessary at this point to up date the baseline Widal titres in apparently healthy children of Davangere. These titres can be used as a cut off titre for the diagnosis of typhoid fever.

» Materials and Methodology

The study was conducted at the department of pediatrics J.J.M. Medical College, Davangere. The subjects included 104 healthy children without symptoms and 146 children with minor illness attending the outpatient department not associated with fever (6 months-15 year). This study was a cross sectional survey.

The Widal tube agglutination test was done on all sera using commercially available antigens containing S. enterica subsp. enterica ser. Typhi O and H antigens and S. enterica subsp. enterica ser. Paratyphi A 'H' antigen (SPAN diagnostic private limited). 0.4 ml of two fold serially diluted patients sera (dilution from 1:20 to 1:320) in 0.9% normal saline was tested by adding an equal volume of antigen. A negative control was included in each batch of the test.

» Results

Widal Titres were assessed for 'O' and 'H' antigen of S. enterica subsp. enterica ser. Typhi and 'H' antigen of S. enterica subsp. enterica ser. Partyphi A.

showed that no child in the age group 6 month-2 years showed Widal titre of 1:80 for both O and H antigen and all children showed a titre of <1:20 for AH antigen. In other age groups only a small percentage showed 1:80 titre for O and H antigen of S. enterica subsp. enterica ser. Typhi like 5%, 3% , 6% and only few showed a titre of 1:20 for AH antigen.

These observation were same in healthy children as well as non typhoidal fever cases. Hence, the values were combined and put in one table.

» Discussion

Enteric fever still remain a major endemic health problem in India. Isolation of S. enterica subsp. enterica ser. Typhi has remained as the gold standard, however it is well recognized that facilities for culture are not readily available or limited in many areas. Although the culture method is gold standard, it is however time consuming, expensive and the culture positive cases are also very less and hence the best alternative is the Widal Test.

When interpreting the Widal test it is of utmost important that the test be interpreted against the background of normal titre of the population in a particular area. These titres may also vary among the endemic areas and with time. So each country, or region should have the baseline titres of their healthy population which should be updated with time.

In the present study, highest level of Widal titre was found upto 1:80 for both O and H antigen, in all age groups, except in age group 6 month to 2 year the highest level of Widal titre was found upto 1:40 i.e. no titre was found at 1:80 dilution in 6 month to 2 year age for both O and H antigen. 96% had titre equal to or less than 1:40 to O antigen and 96% had titre equal to or less than 1:40 to H antigen.

The results were in agreement with the results obtained by others workers, like Kulkarni et al

Cause for the differences in the antibody response may be due to the factors like poorly standardized antigen preparation, technical difference, the sharing of the antigenic determinants with other Salmonella More Detailse and effects of treatment with antibiotics and previous immunization with TAB vaccine may be contributed.

Another major problem relates to the difficulty of interpreting Widal test results in areas where S. enterica subsp. enterica ser. Typhi is endemic and where the antibody titres of the normal population are often not known. Furthermore in areas where fever due to infectious causes is a common occurrence, the possibility exists that false positive reactions may occur as a result of nontyphoidal fever.

The present study reveals that the Widal test is still of significant diagnostic value provided if the titres are interpreted on the knowledge of baseline titres in that area and time. Even today, Widal test remains one of the best, easily accessible, cheap and simple method for the diagnosis of typhoid fever and thus help in reducing morbidity and mortality from typhoid.

» Conclusion

No Widal titre were found at 1:80 dilution in 6 month to 2 year of age for both O and H antigen of S. enterica subsp. enterica ser. Typhi. Age did not influence the Widal titres in older children (> 2 year).

The baseline titre for 6 month to 2 yer age group is 1:40 for both O and H antigen of S. typhi . The baseline titre for children (> 2 year) is 1:80 for S. enterica subsp. enterica ser. Typhi antigens. The baseline titre for S. enterica subsp. enterica ser. Paratyphi A 'H' antigen is < 1:20 for 6 month to 2 year. The baseline titre for S. enterica subsp. enterica ser. Paratyphi A 'H' antigen is 1:40 for children more than 2 year. The Titre anything above the baseline titre can be taken as diagnostic titre for the diagnosis of enteric fever.