Assessment of sensitivity, specificity and predictive value of Widal test in Typhoid fever patients in Hamadan

Serological Widal test is a fast, reliable and easy to perform and this test still is a suitable diagnostic method for diagnosing of typhoidal disease in many clinical laboratories. However, there are some doubtful reports regarding diagnostic value and credibility of this test, which was a motivation for present research. In this study, a total of 378 patients in two groups including 182 typhoidal patients with positive culture for Salmonella Typhi and para-Typhi A, B, C and 196 non-typhoidal febrile patients with negative culture for Salmonella, were studied in Hamadan city during 1994-97. All patients had at least one Widal test. In first group, 52.7% of patients have a titer of? 1:40 using anti-O (A, B, D) and 42.3% of patients also have a titer of? 1:80 using anti-O (A, B, D). In second group, 7.2% of patients have a titer of? 1:40 and 5.6% of them have a titer of? 1:80. In first group, 66.4% of patients had positive blood culture for S.typhi, however, 31.3% of them had positive antibody for OD titer. The results of this study indicated that sensitivity of Widal test for titer of? 1:80 was 86%, specificity 64% and PPV 42% and NPV 95%, therefore the negative Widal test did not have significant effect on the clinical diagnosis of typhoid disease.