The Widal test is a diagnostic process that is used to identify typhoid fever or enteric fever. The test does that by detecting the presence of particular antibodies in the blood that indicate an infection caused by Salmonella Typhi or Salmonella Paratyphi. A significant increase in antibodies that titers over time, or a high initial titer, usually indicates a current infection! Widal test is especially useful in locations with limited access to advanced diagnostic facilities because this test provides a straightforward and accessible way for detecting the infection, which can quickly assist in prompt treatment decisions.
The Widal test is a serological test used to detect typhoid fever, which is caused by the Salmonella typhi and Salmonella paratyphi bacteria. It identifies the presence of particular antibodies (agglutinins) in the blood, which the immune system generates in response to that particular infection! The test works by combining the patient's blood serum with recognized bacterial antigens, especially the O (somatic) and H (flagellar), and during the test, if agglutination (clumping) happens, it suggests the presence of these antibodies. This implies an active or previous infection and a fourfold rise in antibody titers in tests collected 10-14 days apart completely supports the diagnosis.
Remember, a single Widal test result is not necessarily definitive, and that’s why it must be considered in conjunction with clinical symptoms and other laboratory results! Despite its extensive usage, the Widal test has certain drawbacks, such as giving false-positive findings in those who have been vaccinated against typhoid or have already been sick before. Furthermore, false negatives can occur in the early stages of illness, before the body produces measurable antibody levels, which can derail the treatment!
What’s more, cross-reactivity with different illnesses might also provide inaccurate findings in certain cases. Because of all these limitations, blood culture remains the gold standard for diagnosing typhoid, however, in resource-constrained areas where blood cultures may be unavailable, the Widal test is still highly used as a preliminary diagnostic technique for typhoid disease.
The Widal test procedure includes using either the slide agglutination or tube agglutination method. The test detects the presence of O (somatic) and H (flagellar) antibodies in a patient's serum, which aids in the diagnosis of typhoid in a patient. You should know, no specific preparation, such as fasting, is required prior to the test. During the test, a healthcare practitioner draws blood from a vein in the patient's arm with a sterile syringe and puts it into a simple test tube or serum separator tube (SST). The blood sample is then allowed to coagulate before being centrifuged to extract the serum, which includes the antibodies.
1. Slide Agglutination Method (Rapid Test)
This form of Widal test is a rapid way to obtain qualitative findings, and this evaluates if there is agglutination (clumping), which indicates the presence of antibodies.
Positive Result: Agglutination (clumping) demonstrates the existence of antibodies against Salmonella antigen.
Negative Result: No apparent clumping indicates that the antibodies are missing or at low levels.
2. Tube Agglutination Method (Quantitative Test)
The Tube Agglutination Method yields quantitative data by calculating the antibody titer (concentration).
Positive Result: A titer of 1:160 or greater is considered significant and indicates current typhoid illness.
Other Results: Lower titers may suggest a previous illness or immunization.
Widal test findings are interpreted based on antibody titer levels against Salmonella Typhi and Salmonella Paratyphi antigens, as well as the presence of various symptoms in the patient! The Widal test normal range for O and H antigens are:
O (somatic) antigen - 1:40 to 1:80
H (flagellar) antigen - 1:40 to 1:80
If you have O antigen titers ≥ 1:160 and H antigen titers ≥ 1:160, it is considered a Widal test positive result.
Elevated antibody titers, often at or above 1:160, indicate that the body is aggressively fighting the infection, and in certain situations, matched blood samples are analyzed for a fourfold increase in antibody titers, which can then help prove the existence of a current infection.
As we have already mentioned, this test is used to detect typhoid fever in a patient, and because of its easy availability in areas where modern testing facilities are not present, this test can produce instant results!
The following are the primary advantages of the Widal test:
The Widal test is an important diagnostic tool for typhoid fever, especially in areas where modern diagnostic methods are not always available or are highly expensive. In India, it is quickly performed, inexpensive, and widely available, the factors that make it an effective tool for early identification of typhoid fever.
If your doctor has prescribed a Widal test, contact Pathkind Labs today! The lab offers the Widal test at a very affordable price, and their modern, cutting-edge facility produces accurate results without fail !
Discover precision diagnostics with Pathkind Labs, a trusted name in diagnostic services in India. Our NABL accredited labs, equipped with advanced technology, are staffed by a certified team of over 200+ senior pathologists and 2000+ technicians. From tailored health check-ups to specialized tests in Oncology, Neurology, Gynaecology, Nephrology, and more, we've got your health covered. Skip the hassle with online booking for tests or check-ups, available for both lab visits and at-home blood collection. For a seamless experience and early detection, choose Pathkind Labs in Gurugram. Book your appointment today and experience diagnostics made easy.
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