Widal Test

Widal test is mainly used as a diagnostic method to check for typhoid fever. The condition spreads through contaminated food and water and presents with the following symptoms:

• Fever with a temperature between 103 and 104°F for more than 2 days
• Stomach pain, loss of appetite
• Diarrhoea or constipation
• Weakness and headache
• Cough
• Some people may even develop rashes on the skin

If you present with any of the following symptoms, your doctor may ask you to get a Widal test done to check if you have an S.typhi infection.

You don't really need any special preparations for a Widal test. Before the test, it is important that you inform your doctor if you have had any previous vaccination or immunisation to typhoid fever. It is also crucial to let the doctor know about the presence of any other infections, like malaria, or if you have been in close contact with a person infected with the typhoid causing bacteria. These factors would be helpful in the correct diagnosis of typhoid fever

(Health checkup app)

The testing procedure is performed on blood serum. Therefore, a blood sample needs to be collected from the person. Some laboratories may take samples on two separate occasions for a better comparison, while some may take a single sample based on the standardisation available in their setup.

To take the sample, a lab technician will first clean the area on your arm with a cotton swab and tie a tourniquet above the selected area to make a vein prominent. Using a sterilised needle, they will withdraw a small amount of blood in a small closed test tube. Once enough sample is collected, the technician will cover the area with cotton gauze to stop bleeding. Finally, they will put a bandage on the area. 

You might experience slight discomfort due to the prick of the needle, but it will subside soon. Also, there could be some bruising on your skin after the test. This too will also fade away by itself.

If you notice persistent bruising, pain or swelling on the site of sample withdrawal, inform your doctor at the earliest.

Normal results:

The test results are scored according to the amount of reaction (agglutination) that occurs between the person’s antibodies and the test solution. The list given below shows the correlation between test score and result:

• 0 means no reaction
• 1+ means 25% reaction
• 2+ means 50% reaction
• 3+ means 75% reaction
• 4+ means 100% reaction

When the score is 0, it is considered a normal result. It means that the person is not suffering from typhoid fever.

The test also involves the dilution of blood serum to check for the occurrence of a reaction. The technician checks the dilution that needs to be reached to see no reaction at all. Therefore, for the simplicity of interpretation, the dilution may also be stated in the test reports. However, a negative result does not completely negate the chance of infection since it may be due to weak antibody response in a person.

Abnormal results:

A value other than 0 is considered abnormal, and it could mean that the person may have typhoid fever.

Since the sensitivity of the test has been questioned time and again, the doctor may order further tests to ascertain the diagnosis. A blood culture test is nowadays suggested in most developed countries to confirm the presence of S. typhi in a sample. In this test, patient's sample is put on a specialised medium to promote bacterial growth and then the culture is checked under a microscope. 

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.