A Widal test is a simple blood test that may confirm or rule out enteric fever, generally known as typhoid fever. It usually takes 6 to 30 days after being exposed to infection for the first signs of fever to show. Doctors prescribe Widal testing for a number of reasons.
A Widal test is used to identify antibodies against flagellar (H) and somatic (O) antigens that induce infection and typhoid fever. When exposed to certain antigens, the body produces particular antibodies. The Widal test examines the interaction between these antigens and antibodies present in patient blood samples.
What is the use of a Widal test?
There is a possibility of typhoid fever if you have symptoms such as high fever, lethargy,diarrhea,constipation, stomach discomfort, rose spot rashes,dry cough, and headache. Widal test is recommended by doctors in the diagnosis of typhoid illness. Typhoid fever is caused by the Salmonella enterica serotype typhi bacterium. The illness is caused by consuming contaminated food and drink containing feces. The Widal test detects typhoid-causing germs in the patient's bloodstream using an agglutination biochemical test.
Who Should Get This Test Done?
If a patient exhibits signs of typhoid fever, the doctor may prescribe a Widal test to get a more accurate diagnosis. These are some of the symptoms:
- High fever with body pains
- Severe headache
- Constipation
- Abdominal discomfort
- Diarrhea
- Red spots on the body
- Weakness
- Appetite loss
- Agitation, and, hallucinations
How is the Widal Test Conducted?
There is no specific preparation necessary, and no fasting is required. A small needle is delicately inserted into a vein in the arm to get a blood sample. After that, the blood sample is sent to a laboratory for analysis.
Widal Testing Methods
- Qualitative Method : On the slides, one drop of undiluted blood serum is deposited, followed by one drop of O, H, AH, and BH antigens. The slide is gently shaken for a minute after the ingredients have been mixed using a separate applicator stick. If there is no agglutination, the test is declared negative.
- Quantitative Approach : Following a positive qualitative test, a semi-procedural Widal tube test is performed, which comprises evaluating the positive antigens with a blood sample to confirm slide agglutination.
Because of its higher sensitivity but poorer specificity, the slide Widal test should be used for screening, but positive slide test findings should be validated by the tube Widal test.
Understanding Test Ranges and Results
The titer value can be used to analyze a Widal test since it requires detailed and exact interpretation. To achieve a typhoid test result, titers ranging from 1:20, 1:40, 1:60, 1:80, 1:160, and 1:200 must be included in the diagnosis.
Negative Result - When the value of the O and H antigens is less than 1:160, the result is called negative and is typically regarded to be within the normal range for a Widal test.
Positive result - A positive result is present when the titer of O and H antigens is greater than 1:60 to 1:320. A positive Widal test result indicates that salmonella typhi is present in the blood.
The Widal test is a brief and affordable method to screen for typhoid illness, even in remote areas where medical care is limited.
Typhoid fever is increasing in urban and rural areas of developing nations due to poor sanitation and a lack of safe drinking water. However, the sickness can be readily managed if the typhoid patient is examined promptly and carefully cared for with a specialized diet and frequent treatment.
