Is the Widal Test Still Useful?

Kim, Sun E; Kim, Think You; Park, Ile Kyu; Kang, Jung Oak; Yeal, Tae

Abstract

BACKGROUND
Widal test has been one of the most important diagnostic tests for typhoid and is still widely used. Widal test has been useful diagnostic tool for typhoid in endemic areas, while it has been largely abandoned in developed countries. Since 1990, occurrance of typhoid has been markedly decreased in Korea, we studied diagnostic usefulness and criteria of Widal test from 1990 to 1997.
METHODS
Using rapid slide titration method (Stained Salmonella suspensions, Murex Biotech Ltd., Dartford, England), the Widal test was done in 116 nontyphoid salmonellosis patients, 75 patients with proven typhoid fever, and 173 cases of clinically suspected typhoid fever patients. Stastical analysis was done with discriminant analysis in culture proven salmonellosis.
RESULTS
Fifty-four culture proven cases of Salmonella paratyphi (S. paratyphi) A and S. paratyphi B showed no significant cutoff value in O antibodies. Salmonella typhi (S. typhi) O titer at the 1:160 and above showed lower sensitivity (37.3% vs. 69.3%) and specificity (91.4% vs. 93.1%) compared to S. typhi H titer at the 1:320 and above in diagnosis of culture proven cases of typhoid. We applied D (0.01xH titer+0.001xO titer-1.635) score which result from discriminant analysis. Positive D score (> or =0.21) showed sensitivity of 72% and specificity of 92.2% in culture proven cases of typhoid. In clinically suspected patients, positive D score showed 39.3% of sensitivity.
CONCLUSIONS
We concluded that the Widal test for O antibodies of S. paratyphi A and S. paratyphi B is not useful for diagnosis of paratyphoid fever. In the present study S. typhi H antibodies are more diagnostic than S. typhi O antibodies. We appled D score and positive D score showed increased sensitivity of Widal test than application of O antibody titer.