Why is it in the News?

The Widal test's tendency to produce inaccurate results is clouding the understanding of India's typhoid burden, leading to increased costs, and exacerbating antimicrobial resistance risks.

What is the Widal Blood Test?

• A Widal test is a serological diagnostic test for typhoid fever.
• It helps evaluate the level of antibodies produced by the body in response to the Salmonella bacterial infection that causes typhoid fever in patients.
• Widal blood test is also known as a typhoid blood test report, as it is widely used for diagnosing typhoid fever.
  • The symptoms of typhoid fever may be similar to those of other diseases, which can make the diagnosis of typhoid difficult without proper testing.
• Typhoid fever is a severe illness caused by a bacterium called Salmonella Typhi.
• This bacterium affects the gastrointestinal system and causes a range of symptoms such as high fever, diarrhoea or constipation, headache, abdominal pain, fatigue, weight loss, and red spots.
• The bacteria usually enter the body through contaminated food or water.
  • Typhoid requires prompt treatment to prevent further complications such as severe intestinal perforation or bleeding.
• The Widal blood test is a quick and easy serological test that can help confirm or rule out whether a fever is due to a typhoid infection.
• Typically, typhoid symptoms appear within 6 to 30 days of exposure to the bacterial infection.
• The Widal test is designed to detect antibodies against O (somatic) and H (flagellar) antigens that cause the infection and typhoid fever.
• Infection through these antigens produces specific antibodies in response.
• The Widal blood test analyses the interaction between these two antigens and the antibodies produced in the patient's body through a blood sample.
  • Detecting the presence of these antibodies in the Widal blood test indicates a bacterial infection.
• However, it has several limitations and has been phased out in many countries due to its potential for inaccuracy.
• The World Health Organization (WHO) advises against relying heavily on the Widal Test because various factors can influence its results.
  • For example, a single positive result does not definitively confirm an active typhoid infection and a negative result does not necessarily rule it out.
• Additionally, obtaining an accurate diagnosis requires testing at least two serum samples taken 7-14 days apart, which can be time-consuming and often impractical.
• In areas with a continuous high burden of typhoid, baseline antibody levels may already be elevated, complicating the interpretation of results without knowing the appropriate cut-off values.
  • Furthermore, cross-reactivity with antibodies produced against other infections or vaccinations can lead to false positives.
  • Prior antibiotic therapy can also impact antibody levels, resulting in false negatives.
• Despite its accessibility and historical significance, the Widal Test's limitations emphasize the need for more accurate and reliable diagnostic methods for typhoid fever.