Widal test (Slide method)
Booked 1108 timesAlso known as:
Typhoid test, Widal agglutination test
Blood
No
Serum
Description
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Overview
Strong immunity is key to living a happy life. The immune system protects our body from external sources which can harm our body, such as bacteria, etc. However, when an individual happens to consume contaminated food, it can have varying adverse effects on the body, including ingestion of bacteria like Typhoid and Paratyphoid.
An individual can also get infected by Typhoid by using a toilet that is contaminated with bacteria and touching body parts without washing hands, contaminated milk products, unhygienic street food and carrier cases those asymptomatic. Typhoid fever or Typhoid is caused by Salmonella typhi bacteria.
Typhoid occurs 8 to 48 hours after the bacterial infection and remains 2 to five days. A patient with Typhoid carries the bacteria in their bloodstream and intestinal tract. It's an acute, life-threatening and fever-causing illness. Typhoid fever is often confirmed through blood testing. Widal test (or Typhidot test) is a rapid serological test for the diagnosis of Typhoid.
The Widal test is performed through the slide method. When the typhoid bacilli are mixed with the blood sample containing typhoid antibodies from a patient with Typhoid, agglutination occurs. This means the presence of typhoid bacteria.
Physicians may recommend the Widal test when they suspect Typhoid. This test can quickly diagnose if a patient is affected by enteric or Typhoid fever. If a patient has the symptoms of fever with chill, fatigue, headache, abdominal pain, constipation, weight loss and rash spots, the doctor may recommend a Widal test to the person.
Other names of the Widal test
- Typhoid test
- Typhidot test
- Widal agglutination test
What does the Widal test detect/measure and who is this prescribed for?
Widal test detects Typhoid or paratyphoid infection.
The following symptoms can prompt the consulting physician to prescribe you for a Widal test:
- Headache
- Stomach pain, vomiting and nausea
- Rash
- Extremely swollen stomach
- Diarrhoea or constipation
- Sweating
- Weakness and fatigue
- Muscle aches
- Dry cough
- Loss of appetite and weight loss
Without treatment, you may:
- Become restless and irritable
- Feel exhausted and lie motionless in what’s known as the typhoid state
Other possible complications include:
- Inflammation of heart muscle or pancreas
- Kidney or bladder infections
- Pneumonia
- Infection and inflammation of the membranes
- Psychiatric problems, such as restlessness, hallucinations
Life-threatening complications often develop at this time. Visit a doctor immediately if you think you might have typhoid fever.
Test Result Interpretation
If the antibody against the bacteria is present within the patient’s serum, it'll react with the respective antigen within the reagent and provide visible agglutination (clumping) on the test slide. The highest dilution of the patient’s blood sample that provides a clear agglutination with the Widal test antigen suspensions is that of the antibody titre.
If the Widal test is positive, it indicates that the person has the Salmonella enterica serovar Typhi infection. During a positive report, which indicates the presence of the Typhoid infection and test reflects the presence of both O and H antigen titres. S typhi O positive means active infection of typhoid. Active infection is a sign of an infection of Salmonella enterica serovar typhi. S typhi H positive shows the results of the immunised person’s serum test report or means there's a past infection
A titre of 1:80 or more for O agglutination and 1:160 or more for H agglutination in the blood sample indicates active infection. If the blood samples taken after a duration of 10 days from the original sample show a rise in titres (4-fold or more), it confirms the diagnosis.
Widal test negative means that a person does not have enteric/typhoid fever and there is another infection causing the symptoms. If the titre value of antigen O and H is below 1:160 in the sample, the result is a negative Widal report. The interpretation of the Widal test depends upon the lab conducting the test, as most labs have different values for interpretation.
The results of a Widal test are heavily influenced by the extent of the patient’s last known contact with typhoid antigens. The lesser the extent of the previous contact, the greater is the accuracy of the Widal test.
Sample Type
Widal test requires blood sample, which is collected by phlebotomists by venipuncture of the arm.
Test Preparation
Before the test
If you're on any medications, inform the doctor. No other specific preparations are required before the Widal test.
During the test
The procedure for sampling blood for a Widal test is analogous to other general blood tests. A Phlebotomist collects the blood from the vein of the arm under all aseptic precautions. This process barely takes 5 minutes.
After the test
After the sample is taken, the purpose of contact is cleaned and pressure is applied on the spot to prevent any bleeding. There's little to no risk from this test and there are not any post-test restrictions.
Test inclusion: What parameters are included?
Widal test is done to detect antibodies within the blood sample against antigens O & H of bacteria. Agglutination is the clumping of a particular antigen with its antibody in the presence of appropriate conditions. Slide agglutination and tube agglutination are two ways of administering this test.
A Widal test should be performed after the first week of infection. The reason for this is that the antibodies against “O” and “H” antigens start appearing in the blood at the peak of the first week of fever. It is advised to get two blood tests at an interval of 7 to 10 days.
Risk Assessment
Typhoid and Paratyphoid fever
Price/Cost
The price of a Widal Test can differ based on the city and the laboratory. Typically, a Widal test falls within the range of INR 129 to INR 275. For a better understanding, here is the average cost of a Widal test in some major cities in India:
City | Min Price | Average Price | Max Price |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 | |
129 | 202 | 275 |
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Frequently Asked Questions
What are O and H in the Widal test?
“H” and “O” antigens of Salmonella Typhi and “H” antigens of Salmonella Paratyphi are the antigens used for the purpose of conducting the test. In the case of an acute infection, it is generally observed the O antibody starts to appear and rise rapidly, later falling and often disappearing within a few months. H antibody appears a little later but takes longer to disappear. Rising O antibody titre generally is a sign of acute infection, whereas raised H antibody helps diagnose the type of enteric fever. Widal test should only be performed after one week of infection. The rationale being the antibody against “O” and “H” antigens of the bacteria start appearing in blood at the top of the first week of fever.
How is Typhoid diagnosed by a Widal test?
Widal test is a blood test to detect antibodies within the serum (blood sample) against two antigens (O & H) of bacteria. Agglutination is the clumping of a particulate antigen with its antibody in the presence of appropriate conditions. Slide agglutination and tube agglutination are two ways of administering this test. “H” and “O” antigens of typhoid bacillus and “H” antigens of Salmonella Paratyphi are the antigens utilised in the test.
Why is the Widal test not recommended?
The Widal test has a few limitations: If a person has been previously vaccinated for Typhoid, it may result in increased antibody titres in the non-infected persons. In some cases, False positive Widal tests have been observed in patients with non-enteric infection, for example, Typhus, Immunological disorders, chronic liver disease, Malaria, etc. Any prior use of antibiotics by the patient can affect antibody response during the Widal test giving a low titre even in the presence of bacteriologically confirmed typhoid fever. The Widal agglutination titre has been observed with the geographic location based on the history of Salmonella infection in that area. Another leading cause for False-positive widal test in a person is Past infection with serotype Typhi or another nontyphoidal bacteria.
What is the cause of Widal positivity?
If the Widal test is positive, it indicates that the person has the Salmonella enterica serovar typhi bacterial infection. A positive report indicates the presence of Salmonella enterica; both O and H antigen titres are present. S typhi O positive signifies active infection of Typhoid. Active infection is a sign of an infection of Salmonella enterica serovar typhi. S typhi H positive shows the results of the immunised person’s serum test report or means there's a past infection.
Which disease is confirmed by the Widal test?
Typhoid fever (or enteric fever) and paratyphoid fever are confirmed by a Widal test. A positive Widal test report means active infection. A negative Widal test report means that the person is not infected from typhoid fever.
How frequently should you take this test?
This test should be taken at the advice of a doctor. It's not a daily checkup, hence taking the test frequently isn't required. It's advised by the doctor only if the patient shows symptoms of Typhoid or Paratyphoid.
What is the price of the Widal test?
The Widal test price can range between Rs 129 and Rs 275. However, the price can vary depending upon the locality as well as the availability of discount offers.