Prevalence of thyroid nodules and their associated clinical parameters: A large-scale, multicenter-based health checkup study

Although the confirmative diagnosis of typhoid fever is by culture of the causative organism usually from body fluids, serological test can be helpful in providing a more rapid method of diagnosis. The indirect fluorescent antibody test using a Salmonella typhi Vi-antigen and a FITC-conjugated rabbit anti-human polyvalent immunoglobulins has been evaluated for the diagnosis of typhoid fever. The results obtained were as follows: 1) Only two of 61 sera from culture proved typhoid fever patients were falsely negative. Of 79 sera from patients with febrile diseases other than typhoid fever only one had falsely positive titer. Forty sera from normal subjects were all negative. The sensitivity and specificity were 96.7% and 99.2% respectively. 2) The positive rate of the test was 71.4% within the 1st week, 90.0% from the 1st week to 2nd week, and 100% since the 2nd week after fever onset. 3) The antibody titer to Vi-antigen was already increased within the 1st week after fever onset. And the titer showed its maximum response in the 2nd and 3rd week and was gradually decreased to near normal level throughout this study. In conclusion, the Vi-indirect fluorescent antibody test (Vi-IFAT) could serve as an useful serologic test for the diagnosis of typhoid fever.