Widal Test (Tube Agglutination)

The Widal Test (Tube Agglutination) is a blood test that helps diagnose typhoid and paratyphoid fever, collectively named enteric fever. It helps evaluate the level of antibodies produced by the body in response to Salmonella typhi/paratyphi, the bacteria causing typhoid (enteric fever). By detecting these antibodies, the test can confirm or rule out whether or not an individual has been infected with the bacteria that causes typhoid fever.

The Widal Test (Tube Agglutination) test named after its founder Georges Ferdinand Widal, is a serological test that helps diagnose typhoid fever. This bacterial infection typically presents symptoms  within 6 to 30 days of exposure, including high fever, fatigue, headache, abdominal pain, diarrhea or constipation, weight loss, and a rash known as “rose spots.” These symptoms can resemble those of other diseases, making accurate diagnosis difficult without proper testing. Early diagnosis and treatment are important to prevent serious complications, such as severe intestinal bleeding or perforation. 

The Widal Test (Tube Agglutination) test detects antibodies produced by the body in response to Salmonella typhi antigens - O (somatic) and H (flagellar). This test involves mixing the patient’s blood sample (containing antibodies) with the commercially available stained bacterial antigens and observing for agglutination (clumping) reactions, indicating the presence of specific antibodies. It is suggested to perform this test in the second week of the illness since antibody levels against O and H antigens typically appear in the blood by then. For more reliable results, it is advisable to conduct the test with two blood samples taken 7 to 10 days apart.

Interpretation of test results requires consideration of factors such as the clinical history, vaccination status, and prevalence of typhoid in the region. However, the Widal Test (Tube Agglutination) test has certain limitations and should not be used as a standalone diagnostic test in cases with low antibody titers. It can produce false-positive results due to cross-reactivity with other bacterial infections and false-negatives in early infection or vaccinated individuals. Also, it cannot distinguish between past or current infection. Therefore, it is often combined with other diagnostic methods for a more reliable diagnosis. 

No special preparation is required for this test but inform your doctor about all the medications or supplements that you are taking, as they may affect the test results and may require adjustments or temporary discontinuation. Also, provide your vaccination history to help them correlate your clinical and laboratory findings. 

Test results may vary across laboratories due to differences in methodology and laboratory guidelines. Do not self-medicate at home solely based on these results and always consult your doctor for proper understanding of the test results. The test results will help the doctor tailor your overall treatment plan.