100 years of Widal test & its reappraisal in an endemic area.

A reappraisal of the Widal test was made for its diagnostic utility in typhoid fever in an endemic area of Central India. The significant basal antibody level in the normal population based on 1200 voluntary/relative blood donors at the cut-off titre of 80 or above was observed in 13.83 and 8.0 per cent for 'O' and 'H' antigens of Salmonella typhi respectively. A retrospective study (1991-1995) over 138 bacteriologically proven cases of typhoid showed a positivity of 64.49 and 78.26 per cent respectively for 'O' and 'H' antibodies at the titre of 80 or above and 44.2 and 63.04 per cent at the titre of 160 and above. The retrospective data also showed a greater positivity (46.41%) in 1991 which decreased to 25 per cent in 1995 and appeared to follow the incidence of multi drug resistant S. typhi over the period. The detection of 'H' antibodies is no less important than the 'O' antibodies in the present study. Our data bring out the diagnostic limitations of Widal test done on single samples collected in the early phase of illness (4-10 days) from patients suspected to have typhoid in an endemic area of Central India.