Determination of diagnostic Widal titres in Kumasi, Ghana.

Three hundred and seven healthy food handlers and 34 blood-culture positive enteric fever patients were screened for Salmonellae agglutinins using the Widal test. Of the 307 healthy food handlers, only 3 (1.0%) had an anti-O titre of > or = 1/160 and 8 (2.6%) an anti-H titre of > or = 1/320 for Salmonella typhi, but the majority, 214 (69.7%) and 149 (48.5%) had titres of < 1/20 for O and H agglutinins respectively. Similar agglutinin titres were also seen for S. Paratyphi A, B, and C. In the 34 enteric fever patients, for S typhi, based on anti-O titre of > or = 1/160, 25 persons showed a significant titre, a sensitivity of 73.5%, and a specificity of 99.0%. And 21 persons showed a significant titre of > or = 1/320 for anti-H, a sensitivity of 61.8% and a specificity of 97.4%. Based on these findings, titres of > or = 1/160 and > or = 1/320 for anti-0 and anti-H respectively, were considered diagnostic for enteric fever in Kumasi, Ghana.