Comparison of methods for the diagnosis of typhoid fever

Over five years the Bactec radiometric blood culture method yielded Salmonella typhi in 41 of 45 confirmed cases of typhoid fever, 90% of which were from the first culture set taken. Blood clot culture was positive in 18 (41%) of 44 confirmed cases and stool culture in 24 (59%) of 41. The yield from 2189 Widal clot cultures was only 0.03%. There were 68 positive results in 2258 unpaired Widal tests: 23 of them were falsely positive and 13 falsely negative, but in 11 out of 68 cases the Widal was the only positive laboratory test. It is concluded that routine clot culture is not cost effective if a sensitive blood culture method is used, and that the Widal test is useful only in selected patients.