Diagnostic value of a single Widal test.

The Widal test was performed on 90 blood specimens from typhoid fever patients, on 21 blood specimens from nontyphoid salmonellosis patients and on 46 nontyphoid febrile patients. Of 90 typhoid fever patients, 58 (64.4%) had H agglutinin titer of 1:160 or more and 55 (61.1%) had O agglutinin titer of 1:160 or more. Salmonella typhi H and/or O titer of 1:160 or more occurred in 70 (77.8%) of 90 typhoid fever patients and in 5 (23.8%) of 21 nontyphoid salmonellosis. Only one of the 46 (2.2%) nontyphoid febrile patients showed O agglutinin titer of 1:160, a case which was proven subsequently to be a case of systemic lupus erythematosus. Either O or H can reach to diagnostic level during the first week of typhoid fever, and can be helpful in diagnosis of the illness. In view of the high specificity (91.0%), sensitivity (77.8%) and accuracy (83.4%), the Widal test still has value in the diagnosis of typhoid fever.