Widal Slide Agglutination Test

What is the Widal Slide Agglutination Test?

The Widal test is a serologic assay that detects antibodies (agglutinating antibodies) against the Salmonella O (somatic) and H (flagellar) antigens in a patient’s blood. It is traditionally used to support the diagnosis of typhoid fever and paratyphoid fever.

Key Parameters Reported

Why is this test done?

• Suspected typhoid or paratyphoid fever based on fever, abdominal pain, or travel history.
• To support a clinical diagnosis when other laboratory findings are inconclusive.
• In some settings, to monitor antibody levels during treatment or after vaccination.

Early Detection

The test can help identify signs of typhoid/paratyphoid infection, but it does not diagnose on its own. A doctor interprets the result together with symptoms, history, and other laboratory tests.

What an abnormal result may mean

• Elevated titres may suggest a recent or current Salmonella infection, but can also be influenced by prior exposure, vaccination, or cross‑reacting infections.
• Low or normal titres do not rule out typhoid fever, especially early in the illness when antibodies have not yet risen.
• Many factors—hydration status, concurrent infections, medications, and individual immune response—can affect antibody levels.

Who might be advised to get this test?

• Travelers returning from endemic areas with fever and gastrointestinal symptoms.
• Patients with unexplained prolonged fever, abdominal pain, or rash.
• Individuals in outbreak investigations or public health surveillance.

In short: The Widal test measures antibodies against Salmonella antigens to aid in diagnosing typhoid/paratyphoid fever, but results must be considered alongside clinical findings.

Preparation

• Fasting: No fasting required.
• If combined with fasting tests: Follow the strictest fasting instruction among the tests.
• Procedure: A healthcare professional draws a small amount of blood (typically 5–10 mL) from a vein in the arm using a needle. The sample is then processed in the lab to measure antibody titres.
• Discomfort: A brief needle prick; mild soreness may occur at the puncture site.
• Precautions: No special medication timing or hydration restrictions are needed for this test. Avoid alcohol or strenuous exercise only if advised for other concurrent tests.
• Note: Confirm specific preparation instructions with your doctor or the laboratory. This information is general educational content and not a substitute for professional medical advice.

• Fasting: No fasting required.
• Combined tests: If you are also having a test that requires fasting, follow the fasting instructions for that test.
• Procedure: A healthcare professional will draw a small amount of blood (usually 5–10 mL) from a vein in your arm using a needle. The sample is then processed in the laboratory.
• Time: The blood draw takes about 5 minutes; laboratory processing may take 1–2 hours.
• Discomfort: You may feel a brief pinch or sting when the needle is inserted. The site may be sore for a short time.
• Precautions: No special precautions are needed. Avoid strenuous exercise or alcohol 24 hours before the test if you are also undergoing other tests that require such restrictions.
• Note: Confirm any specific preparation instructions with your doctor or the laboratory. This information is general educational material and not a substitute for professional medical advice.