Usefulness of the Widal test in diagnosing childhood typhoid fever in endemic areas

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Abstract
Data are presented for 2382 children investigated for fever in a Malaysian hospital between 1984 and 1987 when Widal tests and blood cultures were a routine part of every fever screen. There were 145 children who were culture positive (TYP‐CP) for Salmonella typhi, while 166 were culture negative but were diagnosed as having typhoid (TYP‐CN). Analyses of the sensitivity and specificity of combinations of initial Widal titres in predicting a positive S. typhi culture in a febrile child (culture positive vs the rest) showed the best model to be an O‐ and/or H‐titre of ≥ 1 in 40 (sensitivity 89%; specificity 89%). While the negative predictive value of the model was high (99.2%) the positive predictive value remained below 50% even for very high titres of O and H (> 1 in 640), at which point the specificity was 98.5%, supporting the clinical view that a high proportion of the TYP‐CN patients really were typhoid but were missed by culture. The TYP‐CN patients showed a very similar clinical and age profile to TYP‐CP patients. The length of history of fever did not affect the initial Widal titre in culture positive cases. The Widal test in children remains a sensitive and specific ‘fever screen’ for typhoid although it will not identify all cases. In children, lower cut‐off points for O‐ and H‐titres should be used than are generally recommended.