Diagnostic value of Typhi dot test for diagnosis of typhoid fever in Vietnamese patients

Abstract

A Dot Enzyme Immunoassay (EIA) using 50-KD-outer membrane proteins (OPMs) of Salmonella typhi was evaluated and compared with Widal test for the serodiagnosis of typhoid fever in 73 typhoid fever cases (blood culture positive for Salmonella typhi) and 323 non-typhoid fever cases admitted to LongXuyen and Cailay hospitals from 1/7/1999 to 15/5/2000. Besides that EIA and Widal test were also done in 22 patients with clinical feature of typhoid fever but blood culture was negative. The results showed that: Sensitivity of EIA (78.1%) is better than Widal test (61.6%). Specificity of two tests are similar. (81.1 % of typhi dot and 79% of Widal tests) Positive predictive value of EIA and Widal tests are: 48.3% vs 39.8%. Negative predictive value of EIA and Widal tests are: 94.2% vs 90.1% False positive of EIA and Widal test are: 18.9% vs 21.1% False negative of EIA and Widal tests are: 22% vs 38.4%. In the high possibility of typhoid fever group o f 22 patients EIA is positive in 74.5% and Widal is positive in 59%. In conclusion, the dot EIA offers more advantages in terms of simplicity, speed, economy and flexibitity when compared with Widal test.