From the Guidelines
The Widal test does not have good specificity for diagnosing typhoid fever in India, and its use is not recommended as a standalone diagnostic tool. The Widal test has several limitations that affect its specificity, including:
- Cross-reactivity with other Salmonella species and non-typhoidal infections
- High background antibody levels in the population from prior exposure or vaccination
- Varying cut-off titers used in different laboratories As stated in the study 1, the serological Widal test lacks sensitivity and specificity and is not recommended. Instead, blood culture remains the gold standard for diagnosing typhoid fever, with a higher sensitivity than the Widal test 1. Other tests like PCR or rapid diagnostic tests (e.g., Typhidot) may be used in conjunction with clinical presentation to improve diagnostic accuracy. A combination of clinical features, epidemiology, and multiple laboratory tests is the best approach for diagnosing typhoid in endemic regions like India. If typhoid is suspected clinically, empiric antibiotic treatment (e.g., ceftriaxone 2g IV daily for 10-14 days) may be initiated while awaiting confirmatory test results, especially in severe cases or areas with limited diagnostic capabilities 1.
From the Research
Widal Test Specificity in Diagnosing Typhoid Fever in India
- The specificity of the Widal test in diagnosing typhoid fever in India has been evaluated in several studies, with varying results.
- A study published in 2014 in the Journal of Clinical and Diagnostic Research found that the Widal test had a specificity of 47.31% in pediatric patients 2.
- Another study published in 2014 in BMC Research Notes found that the Widal test had a specificity of 68.44% in febrile patients 3.
- A study published in 2006 in Diagnostic Microbiology and Infectious Disease found that the Widal test had a specificity of 85% when using an anti-TO titer of 1/80 as the cutoff value 4.
- A study published in 2001 in the Japanese Journal of Infectious Diseases found that the Widal test gave a high proportion of false positive results, indicating low specificity 5.
- A study published in 2011 in Annals of Clinical Microbiology and Antimicrobials found that the specificity of the Widal test varied depending on the brand used, with some brands giving higher specificities than others 6.
Factors Affecting Widal Test Specificity
- The specificity of the Widal test can be affected by various factors, including the brand used, the cutoff value, and the population being tested.
- The use of different brands of Widal test kits can result in varying specificities, as found in the study published in 2011 in Annals of Clinical Microbiology and Antimicrobials 6.
- The choice of cutoff value can also affect the specificity of the Widal test, as found in the study published in 2006 in Diagnostic Microbiology and Infectious Disease 4.
- The population being tested can also affect the specificity of the Widal test, with pediatric patients and febrile patients having different specificities, as found in the studies published in 2014 in the Journal of Clinical and Diagnostic Research and BMC Research Notes, respectively 3, 2.