Evaluation of Widal test and Tubex for diagnosis of typhoid and paratyphoid A

Objective To evaluate the efficiency of Widal test and Tubex detection on diagnosis of typhoid and paratyphoid A. Methods Serum samples collected from the blood culture confirmed cases of typhoid and paratyphoid A in Guangxi, Xinjiang and Yunnan provinces during the outbreaks were used for Widal test and Tubex (Tubex-TF and Tubex-PA) detection of the specific antibodies against Salmonella Typhi and Salmonella Paratyphi A. The diagnostic accuracy of the three methods was evaluated with the culture method as the gold standard. Results The results showed that for 23 culture-confirmed typhoid cases, the sensitivity and specificity of Tubex-TF were 82.61% and 61.64%, respectively, with the positive predictive value of 40.40% (PPV) and negative predictive value (NPV) of 91.80%, and Tubex-PA showed 91.30% positive detection rate. While for 71 culture-confirmed paratyphoid A cases, the sensitivity and specificity of Tubex-PA were 74.65% and 16.00%, respectively, with PPV of 71.60% and NPV of 18.20%. The positive detection of Tubex-TF was 39.44%. The combined positive detection rate of Tubex-TF and Tubex-PA for typhoid and paratyphoid A was 80.21%. Compared with the high detection rate of Tubex, Widal test showed lower detection rate (6.00%) for typhoid and paratyphoid A(2=75.165, P=0.000). Conclusions During the outbreak or epidemic, besides Widal test, Tubex-TF can be used in early detection of typhoid, while the its effect in early serological diagnosis of paratyphoid A needs further research.