What Is the Widal Test and Why Is It Done?

Fever is one of the most common health complaints. While most fevers are short-lived, some can signal an underlying infection that needs careful attention. One such infection is typhoid fever, caused by Salmonella Typhi bacteria. To detect this condition, doctors may recommend a screening called the Widal test.

Let’s learn more about this medical diagnostic test.

What Is the Widal Test?

Widal test is a blood test that helps in the diagnosis of typhoid and paratyphoid fever. The test works by detecting specific antibodies in the blood that the body produces when it encounters Salmonella Typhi or Salmonella Paratyphi bacteria.

Although it has been used for decades, the Widal test is generally considered a supportive tool rather than a standalone diagnostic method. It is often performed in areas where typhoid is common and advanced tests may not be easily available.

Why the Widal Test Is Done

The main purpose of this test is to assist doctors in identifying infections caused by typhoid and paratyphoid bacteria. In simple terms, the Widal test is used for:

• Detecting antibodies against Salmonella bacteria.
• Supporting the diagnosis of typhoid fever.
• Helping differentiate typhoid from other conditions with similar symptoms.

Widal test is like a bigger diagnostic approach, often supported by medical history, physical examination, and other laboratory findings.

The Widal Test Procedure

The procedure is straightforward and minimally invasive:

1. A healthcare professional collects a small sample of blood from a vein in the arm.
2. The blood is then analysed in the laboratory to check for antibodies that react with antigens of Salmonella Typhi (O and H antigens) and Salmonella Paratyphi (A and B antigens).
3. The strength of the reaction, known as agglutination, helps estimate the level of antibodies.

The process is simple and usually does not take long. No special preparation is needed before giving the sample.

Understanding Widal Test Results

Interpreting the Widal test results requires medical expertise. Generally, the presence of higher antibody levels suggests possible typhoid infection. However, results are not absolute and can be influenced by several factors.

• Significant titres: Rising levels of antibodies over time may indicate active infection.
• Single test limitation: A single test result without follow-up may not give a complete picture.
• Local variations: In regions where typhoid is common, people may already have low levels of antibodies due to past exposure or vaccination, which can affect interpretation.

Because of these variables, doctors often rely on repeated testing or combine the Widal test with other investigations before confirming typhoid fever.

Factors That May Affect Accuracy

Several factors can influence how reliable the Widal test is:

• Prior typhoid vaccination may produce antibodies that appear in the test.
• Past infections can leave behind antibodies that cause false-positive results.
• Other infections may sometimes trigger cross-reactions.
• Timing of the test matters; performing it too early may not detect antibodies.

This is why the Widal test is considered more useful as part of a series of evaluations rather than a single standalone test.

Cost of Widal Test in India

The cost of this test in India can vary depending on the city, type of healthcare centre, and whether it is performed in a private or government laboratory. On average, it costs around ₹200 to ₹300, but may go up to ₹600 at some diagnostic centres. The test is relatively affordable compared to advanced diagnostic methods, making it a commonly used option in many regions.

To Wrap Up

The Widal test has been a longstanding method for screening typhoid fever. While it is not the only diagnostic tool, it remains useful in areas where advanced tests are not easily accessible. By understanding about the Widal test and why it is done, patients can approach the process with more clarity.

For accurate diagnosis and the right treatment, it’s always best to consult a qualified healthcare professional who can explain the test in the proper context. You can easily book an appointment for a Widal test online through the Apollo Diagnostics app or website. This way, you can choose a time that works for you and avoid unnecessary waiting at the centre.