Widal TestWidal Test

Widal Test

Widal Test is method that may used to help diagnose enteric fever. Widal test is an agglutination test which detects the presence of serum agglutinins (H and O) in patients serum with typhoid and paratyphoid fever. Widal Test reveals the presence of salmonella bacteria. Salmonella is actually an intestinal dieses. This fever does not touch normal fever but keeps going up and down. This fever also called step ladder fever. The correct way to diagnose enteric fever is blood, or stool culture. If culture test is not available, a serology test its called widal test. Antibodies of salmonella are present in the patient serum. Widal test can also be done on slide and can be seen in the test tube. The slide method is commonly used.

Widal Test

The traditional Widal test measures antibodies against flagellar (H) and somatic (O) antigens of the causative organism. In acute infection, O antibody appears first, rising progressively, later falling and often disappearing within a few months. H antibody appears a little later but persists for longer. Rising or high O antibody titre generally indicates acute infection, whereas raised H antibody helps to identify the type of enteric fever.

Is This Test Have Other Name

Widal Test, Typhoid Test, Enteric Fever Test,

How The Test Is Performed

A blood sample needed.

Why Test Test Performed

Salmonella is actually an intestinal dieses. Typhoid a dieses of the bowels. It is passed from one patient to others. This fever does not touch normal fever but keeps going up and down. This fever also called step ladder fever. If you have symptoms are.

  1. Vomiting
  2. High Grade Fever
  3. Stomach Pain
  4. Headache
  5. Cough
  6. Lose Motion
  7. Rose Spot

Procedure Of Test

The patient’s serum is tested for O and H antibodies against the following antigen suspensions.
S. Typhi 0 antigen suspension
S. Typhi H antigen suspension
S. Paratyphi A 0 antigen suspension
S. Paratyphi A H antigen suspension
S. Paratyphi B 0 antigen suspension
S. Paratyphi B H antigen suspension
S. Paratyphi C 0 antigen suspension
S. Paratyphi C H antigen suspension


Draw the lick-shaped boxes below on a slide.

Widal Test

One drop in each box O and H antigen. Now add 40 micro liter in the first box and 30 micro liter in second 20 micro liter in third 10 micro liter fourth 5 micro liter in fifth box and mix gently. And shake the slide for five minutes. Now you see which box the clumps appear in. If these clumps have appeared up to box 1:160 and beyond, the test result is positive. And if this test does not appear beyond 1:80 the test is negative.


Widal test is negative in the first week of illness.

What Do The Result Means

If you performed the test once, The titer was low means 1:20 or 1:40, Then after a few days you performed the test again and than titer passed up to 1:80 or 1:160 then it means the test is positive. If either O or H has a titer up to 1:160 the test is positive. And if titer is below 1:160 than results is negative. Some patients do not show any symptoms of typhoid yet the test positive. No need to worry about it. This test is not only specific for typhoid. Rather, a few organisms that resemble the typhoid bacteria due to them also this test comes positive. For example joint dieses, after typhoid vaccine, liver dieses, kidney dieses, etc.

In children’s, O usually comes first. And in adults H comes first positive.

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