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Journal of Clinical Microbiology, September 1999, p. 2882-2886, Vol. 37, No. 9
Wellcome Trust Clinical Research
Unit1 and Centre for Tropical
Diseases,
Received 22 March 1999/Returned for modification 6 May
1999/Accepted 3 June 1999
The diagnostic value of an acute-phase single-tube Widal test for
suspected typhoid fever was evaluated with 2,000 Vietnamese patients
admitted to an infectious disease referral hospital between 1993 and
1998. Test patients had suspected typhoid fever and a blood culture
positive for Salmonella typhi (n= 1,400) or
Salmonella paratyphi A (n = 45). Control
patients had a febrile illness for which another cause was confirmed
(malaria [n = 103], dengue [n = 76], or bacteremia due to another microorganism [n = 156] or tetanus (n = 265). An O-agglutinin titer of
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Value of a Single-Tube Widal Test in Diagnosis of
Typhoid Fever in Vietnam
100 was found in 18% of the febrile controls and 7% of the tetanus
patients. Corresponding values for H agglutinins were 8 and 1%,
respectively. The O-agglutinin titer was
100 in 83% of the blood
culture-positive typhoid fever cases, and the H-agglutinin titer was
100 in 67%. The disease prevalence in investigated patients in this
hospital was 30.8% (95% confidence interval, 26.8 to 35.1%); at this
prevalence, an elevated level of H agglutinins gave better positive
predictive values for typhoid fever than did O agglutinins. With a
cutoff titer of
200 for O agglutinin or
100 for H agglutinin, the
Widal test would diagnose correctly 74% of the blood culture-positive cases of typhoid fever. However, 14% of the positive results would be
false-positive, and 10% of the negative results would be
false-negative. The Widal test can be helpful in the laboratory
diagnosis of typhoid fever in Vietnam if interpreted with care.
*
Corresponding author. Mailing address: Wellcome Trust
Clinical Research Unit, Centre for Tropical Diseases, 190 Ben Ham Tu, District 5, Ho Chi Minh City, Vietnam. Phone: 848 8353 954. Fax: 848 8353 904. E-mail: cparry{at}hcm.vnn.vn.
Journal of Clinical Microbiology, September 1999, p. 2882-2886, Vol. 37, No. 9
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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