Typhoid fever remains a major public health risk withmore than 13 million cases occurring annually in Asiaalone. Delay in diagnosis and institution of appropriatetherapy especially with emergence of multi-drugresistant strains of Salmonella typhi, can be associatedwith significant morbidity and mortality maysignificantly increase the risk of adverse outcome.Traditionally, the isolation of S. typhi remains the goldstandard for diagnosis but, the Widal test continues tobe the most asked for test, despite numerous problemsin the standardization and interpretation.1 The dotenzyme immunoassay for detection of serum antibodiesto S. typhi is rapid, simple and can be interpretedvisually.2 The present study was carried out to evaluatethe typhidot test in comparison with blood culture andthe Widal test in patients admitted in PGIMER,Chandigarh with a clinical diagnosis of enteric fever. In50 consecutive patients with S. typhi isolated in bloodculture, Widal test and dot EIA were performed. A controlgroup of 50 patients with unrelated complaints wereincluded. The Widal test using in-house S. typhi antigenswas considered positive in a single serum sample whenthe S. typhi H antibody titre was = 320 and O antibodytiter was =160. The Typhidot test (MalaysianBiodiagnostic Research SDN BDH, Kuala Lumpur,Malaysia) which detects IgM and IgG antibodies againstS. typhi by using a specific antigen was performedaccording to manufacturer’s instructions. The Widal testin single serum sample was positive in 30 (60%) bloodculture positive patients and was negative in all 50 casesin the control group. IgG and/or IgM was detected bythe typhidot test in 48 (96%) blood culture positivepatients and 7 controls. Both IgG and IgM could bedetected in 15 patients whereas only IgM could bedetected in 30 and only IgG in three. Neither IgG norIgM could be detected in two patients with S. typhiisolation in blood culture. Presence of IgM was a moresensitive indicator, with 45 (90%) being positive for IgMand 18 of 50 (36%) being positive for IgG. Widal test wasfound to be 60% sensitive and 100% specific whereasTyphidot was 96% sensitive and 86% specific whencompared to blood culture. Typhidot had a very highnegative predictive value of 95.55% and positivepredictive value of 87.27%. The diagnostic value of Widalin single serum samples remains a contentious issue.The sensitivity of the typhidot test is much higher thanthe Widal test and is sensitive even in fevers of shortduration.3 The high NPV (95.55%) of the test even in ahighly endemic area is an advantage and can be successfully used even in low-incidence populations.The Typhidot offers advantages of increased sensitivity,rapidity, early diagnosis and simplicity over the Widaltest. Culture isolation remains essential especially forantibiotic susceptibility testing and serological tests forthe diagnosis of typhoid fever can be used in conjunctionwith culture.

Department of Medical Microbiology and *Internal Medicine,Postgraduate Institute of Medical Education and Research,Chandigarh – 160 012, India.Received : 18.5.2005; Revised : 13.10.2005;Accepted : 17.11.2005

REFERENCES

1.Rodrigues C. The widal test – More than 100 years old:Abused but still used. J Assoc Physicians India 2003;51:7-8.

2.Gasem MH, Smits HL, Goris MGA, Dolmans WMV.Evaluation of a simple and rapid dipstick assay for thediagnosis of typhoid fever in Indonesia. J Med Microbiol 2002;51:173-7.

3.Bhutta ZA, Mansur AN. Rapid serologic diagnosis of pediatrictyphoid fever in an endemic area: a prospective comparativeevaluation of two dot-enzyme immunoassays and the Widaltest. Am J Trop Med Hyg 1999;61:654-7.