There is a high level of typhoid or enteric fever misdiagnosis in Nigeria. Patients who come down with a condition that has a fever as its symptom usually diagnose themselves of having typhoid fever and/or malaria. As such, they will walk into a nearby pharmacy and order antimalarial and antibiotics commonly Amoxicillin or ciprofloxacin.
Typhoid fever misdiagnosis is so common that patients tend to treat themselves of the disease together with malaria when once they feel any febrile symptom. This has led to the use of a misleading and incorrect term like “malaria-typhoid” by patients.
Typhoid fever can be diagnosed through various means in the hospital or laboratory. The most common diagnostic test still carried out for typhoid fever is the Widal test.
What is Widal test?
Widal test is a serological test carried out for the diagnosis of typhoid or enteric fever. The test is an indirect agglutination test whereby Salmonella typhi and paratyphi (bacteria responsible for causing typhoid fever) are mixed with a serum that contains specific antibodies like IgG and IgM obtained from the infected person.
In a situation where Salmonella infection is suspected, the test here will be a simple demonstration of the presence of an O-false positive result.
Oftentimes, the chemical 2-mercaptoethanol is added to the Widal test in order to bring about the denaturation of the IgM class of antibodies. If after the application of this substance, a decrease in the titer is observed, it, therefore, means that the contribution of IgM antibody has been removed, thus leaving behind only the IgG component. This helps in the differentiation of a recent IgM antibody from an old infection.
No fasting is required before the Widal test and the test result usually take between 24-36 hours to be out.
What Samples Are Required?
The sample required for the Widal test is a blood or serum sample. The sample collection procedure is basically by venipuncture. Venipuncture is the collection of blood from the vein. The most common site of venipuncture for this procedure is the arm.
What Widal test results mean
When interpreting the Widal test results, it is important to take into consideration any history of typhoid fever, typhoid vaccination, and general antibodies level.
The Widal test is considered to be positive if there is a TO antigen titer of more than 1:160 in an active infection. In the case of patients with past infection or who have been immunized in the past, the test is considered to be positive if the TH antigen titer is greater than 1:160.
In the absence of other tests be it bacteriologic culture or a more specific serology, the observation of a fourfold increase in the titer (example, an increase from 1:40 to 1:640) during the course of the typhoid infection, or the observance of a change from an IgM reaction to an IgG reaction of similar titer, would show consistency with typhoid or enteric fever infection.
It is important to note that a single Widal test is of little clinical relevance in an endemic area like Nigeria. This is because of the high chances of recurrent exposure to the Salmonella bacteria, immunization, as well as cross-reaction from malaria and other Salmonella that do not cause typhoid fever.
Cost of Widal test In Nigeria
The cost of carrying out a Widal test is relatively cheap and very affordable. The price ranges from N1, 000 to N3, 000. The test can be carried out rapidly in most diagnostic laboratories and hospitals within the country.
How accurate is Widal test?
Even though the Widal test has been around for decades, and has also served great needs in medicine, it has now been faced with certain pitfalls that question its accuracy. What the Widal test does is provide a presumptive diagnosis of typhoid fever.
Its test results have brought about some level of misdiagnosis which has contributed to the poor management of typhoid fever. This could somehow be attributed to the non-specificity of the symptoms of typhoid infection as well as the inability of the Widal test to provide enough evidence to show that the experienced fever is caused by Salmonella typhi.
Widal test results are unreliable as there have been cases of people testing positive for the bacteria when they don’t have them. The test however continues to enjoy wide patronage in Nigeria since it is fast and affordable. Widal test is no longer in much use in developed countries like the United States of America, Canada, etc. it has been replaced with more accurate diagnostic tools or procedures.
Alternative Diagnostic test
Other ways of diagnosing typhoid fever include:
- Blood culture
- Stool culture
- Urine culture
- Bone marrow culture
Typhoid fever can be accurately diagnosed by culturing the blood sample of the patient during the first week of the fever. Salmonella typhi produces hydrogen sulfide gas from thiosulfate and as such, they can be easily identified when cultured on a differential media such as bismuth sulfite agar.
About Typhoid fever
Typhoid fever is an acute and life-threatening disease caused by a bacterium called Salmonella typhi. It is characterized most commonly by fever and it is transmitted chiefly via the ingestion of food or water that has been contaminated with feces containing the bacteria from an infected person.
Transmission is prevalent in developing countries where the majority of the population are still depending on water from streams and rivers from cooking, drinking, and other domestic use. These water sources are easily contaminated as stools and urines from infected persons can be washed by running water into these water sources.
Symptoms of typhoid fever include:
- Fever which could be as high as 40 °C (104 °F)
- Non-bloody diarrhea or constipation
- Weight loss
- Abdominal pain and/or distended abdomen
- A rash called “rose spots”
- Intestinal perforation which could result in bleeding in severe cases
- Excessive sweating
- Enlarged spleen
- Enlarged liver
Early diagnosis and treatment are essential to avoid serious complications like intestinal bleeding and liver involvement.
The World Health Organization (WHO) has warned against the full reliability of the results obtained via the Widal test and as such, recommended the use of cultures whenever possible in the diagnosis of typhoid fever. This is because of the various factors that can influence the accuracy of a Widal test.
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