When should you take up Widal test and why to take? Know everything about it

Widal test is the vital test to diagnose Typhoid fever and the procedure involves mixing bacteria causing Typhoid to the blood sample of the person. The blood sample of the person infected with Typhoid will have antibodies. The test is just an assumptive seriological test that detects enteric fever or undulant fever. It helps to find Salmonella infection in the blood. After the test is conducted, the report should be interpreted correctly. The test is an established Typhoid Test to detect the composition of antibody in blood samples of people living in Typhoid endemic regions. If you have high fever and the area is endemic to Typhoid, you must immediately undergo this test. Till the test report is out, the doctor will prescribe certain medicines to control the fever.

It may be that the patient is prescribed other tests along with the Widal. The test result is positive when the TO antigen Titre is greater than 1:160 in the active infection or in the past infection.

Can a singular Widal Test suffice?

A singular Typhoid test holds only a little clinical applicability since there can be cross section reactions in the process. It can be that you have Malaria and not Typhoid. So, other tests are also required to confirm Typhoid. The test may be carried out with two different methods like Tube Agglutination and Slide Agglutination. When compared to Slide Agglutination, the Tube Agglutination test is more precise. When Slide Agglutination test limits to only 1:320 titres, the Tube Agglutination may move up to 1:1280 titres. But, slide agglutination has its own benefits. The test may be conducted at a faster pace whereby the results can be out within 5 minutes time.

How the test is carried out?

There are some steps followed to carry out Typhoid Test:

  • the lab professional prepares serum dilutions for the antigen that needs to be tested
  • it is crucial to use thoroughly clean test tubes. The dilution can start with 1:10 and double through 1:320
  • the background has to be kept black or else light can react with serum
  • 1 ml of serum is mixed to 0.9 ml physiological saline and the serum is diluted further and thinned

The lab professional mixes antigen and serum. The sample is made to rotate for 1 minute. The result can be positive reactive or it may be non-reactive negative.

Limitations of Widal Typhoid Test

  • If the test is performed at the earliest and in the first week, the test result can read negative. This may be so even if you have Typhoid.
  • The ones who already underwent antibiotic treatment might not show the increase in Titre level
  • If you are vaccinated against typhoid bacteria, the result may still show positive reaction. Thus, another test will be required. Vaccinated people don’t show an increase of titre.
  • it can take few days time for the results to come

The test may be conducted at home just like HSV test. The blood sample may be collected right from the home. It helps to detect the presence of H and O agglutinins in the serum of infected person. If the facility for culturing isn’t available, the Typhoid test may be conducted.

Typhoid is caused due to the consumption of contaminated food or water. Salmonella bacteria may invade the intestine and then enter the person’s bloodstream. Similar to this test is Weil Felix Test but the purpose is different.

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