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.

What is a Widal Blood test?

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.

Purpose of Widal Blood test

The Widal blood test is used to detect antibodies produced in response to an infection caused by Salmonella bacteria. This can help diagnose or rule out typhoid fever in a person.

When should you get this Widal blood test?

Typhoid fever, also known as enteric fever, is a life-threatening illness that causes various symptoms. A doctor may recommend a Widal blood test if they suspect a person has symptoms due to a typhoid infection. These symptoms may include:

• Fever and chills
• Body aches
• Severe fatigue
• Headache
• Abdominal pain
• Constipation or diarrhoea
• Loss of appetite
• Small red spots on the chest and abdomen

Another reason for recommending a Widal test is if a person has visited a region where typhoid infection is endemic.

What happens during the Widal blood test?

During a Widal blood test, a blood sample is collected from the patient. Before the typhoid fever blood test report, the patient may be asked to fast for a certain period of time as it is often conducted on an empty stomach. The blood is typically drawn from the inner part of the arm using a needle. A phlebotomist locates an accessible vein and disinfects the area with an alcohol swab. Then, a sterile needle is inserted to draw blood and place it in a vial for further testing.

Procedure for Widal blood test

After obtaining a blood sample from the patient, it is sent to a laboratory for testing. A laboratory technician performs the Widal test by processing the sample using analyzers, which are machines designed to measure the specific antibodies present in the sample. During the Widal blood test, the sample of blood is mixed with an antiserum containing antibodies against the bacteria. If antibodies are present in the blood sample, they will react with the antiserum, causing clumping or agglutination of the red blood cells (RBCs).

Uses of Widal blood test

The Widal blood test provides an assessment of the levels of antibodies O and H present in the blood sample, which can help a doctor determine if there is a bacterial infection causing typhoid.

How to prepare for the Widal blood test?

There may not be any special requirements or preparations for the Widal blood test. However, the treating doctor may recommend certain guidelines to follow for specific patients based on their medical history and current health status.

Values of Widal Blood Test Results

The Widal blood test is measured in titers, which essentially measures the dilution level at which the agglutination response takes place. The titers are presented as a ratio, such as 1:20 or 1:40. This value reflects the level of dilution at which the reaction has occurred. Typically, the higher the titer value, the more antibodies are present in the blood sample.

A titer value above 1:20, specifically 1:160, usually indicates the presence of antibodies in response to both O and H antigens.

Conclusion

Typhoid fever is an acute illness caused by a bacterial infection (Salmonella typhi). It is typically diagnosed by a doctor who considers the type and extent of symptoms, along with the assistance of a blood test—the Widal test, which may be used for the diagnosis of typhoid.

FAQs 

1. What happens during the Widal test?

Ans. The Widal blood test is a serological test used to diagnose or rule out typhoid fever in a person. During the test, the presence of specific antibodies is detected in a blood sample against two strains of Salmonella typhi. If agglutination occurs in the blood sample, it indicates the presence of the Salmonella bacteria responsible for typhoid.

2. How do I know my Widal test is positive?

Ans. The diagnosis of typhoid is ultimately made by a doctor who considers the severity and duration of symptoms in conjunction with the test results. Widal test results are considered positive when the agglutination response exceeds normal levels.