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) orSalmonella 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 ≥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.
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机译：在1993年至1998年之间，对2000例越南传染病转诊医院的越南患者进行了急性期单管维德试验对疑似伤寒的诊断价值。试验患者疑似伤寒且血培养为阳性伤寒沙门氏菌（ n = 1,400）或副伤寒沙门氏菌 A（ n = 45）。对照患者患有高热病，已确证另一原因（疟疾[ n = 103]，登革热[ n = 76]或另一种微生物引起的菌血症[ n = 156]或破伤风（ n = 265），在18％的发热对照和7％的破伤风患者中发现O-凝集素滴度≥100。 H凝集素值分别为8％和1％，O型凝集素效价在83％的血培养阳性伤寒患者中≥100，H凝集素效价≥100时为67％。在这家医院接受调查的患者为30.8％（95％置信区间为26.8至35.1％）;在这种患病率下，H凝集素水平的升高对伤寒的阳性预测值优于O凝集素，截止滴度≥200对于O凝集素或H凝集素≥100，维达尔试验可正确诊断出74％的伤寒血培养阳性病例，但14％的阳性结果为否则为阴性，而10％的阴性结果为假阴性。如果谨慎地解释，维达尔试验可对越南伤寒的实验室诊断有所帮助。
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