Table of contents:
- What is the Widal test?
- The process and how to read Widal's test results
- Is the Widal test accurate for typhoid detection?
- How to improve the accuracy of the Widal test
- Are there other tests to diagnose typhus?
- 1. Tubex test
- 2. Blood or tissue culture
The Widal test is one way that health professionals diagnose typhus (typhus) or typhoid fever. Even though it is called inaccurate, this test is still often done in Indonesia because it is not too costly. Check out the sundries about the Widal test below.
What is the Widal test?
The Widal test is an examination procedure developed by Georges Ferdinand Widal in 1896.This examination serves to detect the amount of antibodies in the body that fight bacteria that cause typhus, Salmonella typhii.
When you complain of typhus symptoms, such as dizziness, abdominal pain, and weakness, the doctor will perform a series of tests to determine a diagnosis. First of all, the doctor will perform a physical examination and ask about medical and travel history.
Travel history is important to see where you got or have been infected with bacteria Salmonella typhii. It is known that typhus is transmitted through unclean environments and habits.
The doctor will then ask you to do a blood test to confirm the presence of bacteria Salmonella typhi on your body. One such test procedure that involves drawing blood is the Widal test.
This examination is done to see the antigen and antibody reaction. Antibodies will show a reaction to antigens that are considered foreign objects by showing clumping (agglutination).
When you get infected Salmonella typhi, the body automatically responds by producing antibodies to fight it.
The process and how to read Widal's test results
This test process is carried out by shedding bacteria Salmonella typhii that's been turned off to your blood serum. Bacteria Salmonella typhii divided into two forms, namely O antigen (bacterial body) and H antigen (flagellum or bacterial locomotion).
When the blood serum contains antibodies, the blood sample will appear clotted. Quoted from the journal published by Medicina, the agglutination reaction shows a positive result, while the absence of agglutination shows a negative result.
A positive test result means that it supports the doctor's diagnosis of typhoid fever. Conversely, if the result is negative, you may not have the condition.
Even so, a positive or negative result alone is not sufficient to describe the Widal test. To get more accurate results, the doctor will measure the titer (presence and amount of antibodies in the blood).
The result of the Widal test titer is represented by a number, such as 1/80, 1/160, or 1/320. The higher the number, the chance of infection Salmonella typhi also getting bigger.
Is the Widal test accurate for typhoid detection?
Although still widely used in Indonesia, the Widal test has many drawbacks as a diagnostic procedure for typhoid fever. The reason is, reading the test in one time is not enough to confirm whether you really have an infection Salmonella typhii.
Widal's test results often collide with other conditions. This means that the result of this examination can either be a false positive or a false negative.
False negative results can occur early in the course of the disease. Apart from the absence of infection Salmonella typhi, these results can also indicate which antibiotic treatment you have been on.
So, you are not necessarily free from infection Salmonella typhii, even though the test results showed negative. These results could mean:
- Malnutrition
- Long-term medication
- Suffering from certain diseases that can reduce endurance
Meanwhile, a false positive Widal test can occur due to an infection or vaccination that you have been through. This means that a positive test does not necessarily mean that you have an infection Salmonella typhii. It could be because you have another infectious disease, such as dengue fever or malaria.
How to improve the accuracy of the Widal test
How to read Widal's test results is indeed not easy for several reasons mentioned above. However, the accuracy of the test for typhus detection may be improved if the test is repeated 10-14 days apart.
A more accurate positive test result is indicated by an increase in the antibody titer 4 times from the first test. For example, tests show the titer has increased from 1/80 to 1/320. This means, you may be positive for typhus.
The world health agency states that it is best not to rely too much on this rapid test for the diagnosis of typhoid fever. WHO recommends culture, if possible.
Are there other tests to diagnose typhus?
Here are other tests that doctors may recommend for the diagnosis of typhus:
1. Tubex test
In addition to the Widal test, your doctor may suggest other rapid examination procedures, such as the Tubex test. This examination is said to have a sensitivity of up to 95% with a specificity of 80%. This means that this test has a promising level of accuracy.
2. Blood or tissue culture
Blood or tissue cultures can also be used to diagnose typhus. This method is done by taking a small sample of blood, feces, urine, or bone marrow. The samples are then placed on a special medium that encourages bacterial growth.
The culture is examined under a microscope for presence Salmonella typhii. Quoted from the Mayo Clinic, bone marrow culture is often considered the most sensitive test for bacteria that cause typhus.
Getting the right diagnosis of typhus is useful for determining treatment options for treating typhus. By getting the right treatment, you can avoid complications of typhus that can endanger life.
