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A commonly used typhoid test can be very misleading

Widal test | Sujith

Typhoid fever is a bacterial infection caused by the bacteria Salmonella typhi. The infection is spread through contaminated food and water and symptoms include fever, headache, fatigue, abdominal pain, and constipation or diarrhea. The typhoid vaccine helps protect against typhoid fever by preventing the bacteria from entering the body. Typhoid fever is treated with antibiotics like many related diseases but proper diagnosis is necessary in order to make sure an effective antibiotic is administered.

If you get sick in a developing country with a fever or diarrhea you may end up being tested for typhoid fever. Unfortunately, depending on what kind of testing is done, the diagnosis may not be very accurate.

The Widal test, also known as the Widal agglutination test, is a diagnostic test used to detect the presence of antibodies against specific antigens associated with Salmonella typhi, the bacteria that causes typhoid fever. However, the test is considered to be unreliable and not recommended for diagnosing typhoid fever. The test has low sensitivity and specificity, meaning it can produce false negative and false positive results. It is also affected by cross-reactivity with other infections such as paratyphoid fever, other Salmonella infections, and other enteric fever. Therefore, other tests such as blood culture, PCR, and ELISA are more reliable and accurate diagnostic methods for typhoid fever.

Dr. Ajay Pandey warns against reliance on the vidal test:

The Widal test is still widely used in some developing countries, particularly in areas where access to more advanced diagnostic methods is limited. This is due to the low cost and ease of use of the test. Despite its limitations, it remains a popular diagnostic tool in these areas.

If you are traveling in a third world country and diagnosed with typhoid fever, ask what method was used to diagnose. If it was the widal test, ask if another method can be used to be 100% certain that it is truly typhoid.

Further reading

Mawazo A, Bwire GM, Matee MIN. Performance of Widal test and stool culture in the diagnosis of typhoid fever among suspected patients in Dar es Salaam, Tanzania. BMC Res Notes. 2019 Jun 5;12(1):316. doi: 10.1186/s13104-019-4340-y. PMID: 31167646; PMCID: PMC6551910.


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