News Excerpt:
The Widal test's tendency to give incorrect results clouds the true picture of typhoid's impact in India. The lack of knowledge about the right time to collect blood samples, inconsistent testing kits, and inadequate quality control worsen the situation.
Typhoid:
- Typhoid fever, also known as enteric fever, is a life-threatening infection caused by the bacterium Salmonella Typhi.
- It is usually spread through contaminated food or water.
- Once Salmonella Typhi bacteria are ingested, they multiply and spread into the bloodstream.
- Symptoms:
- High fever, stomach pain, weakness, nausea, vomiting, diarrhoea or constipation, and a rash.
- Some people, called carriers, may remain symptom-free and shed the bacteria in their stool for several months to years.
- These symptoms mimic those of malaria, dengue, influenza, typhus, etc. each with different treatment modalities.
- If left untreated, typhoid can be life-threatening. According to the World Health Organisation, 90 lakh people are diagnosed worldwide with typhoid every year and 1.1 lakh die of it.
Diagnosis of Typhoid:
- The gold standard for diagnosing typhoid is to isolate the bacteria from a patient’s blood or bone marrow and grow them in the lab.
- Stool and urine samples can also yield the same results but with lower sensitivity.
- Problems with culture test:
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- Cultures are time-consuming and skill- and resource-intensive.
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- Prior antibiotic treatment can also affect the results of cultures.
- It is a common issue due to the indiscriminate use of antibiotics in India.
- Some PCR-based molecular methods are known to be better but are limited by cost, the need for specialised infrastructure, skilled personnel, and the inability to retrieve live bacteria for further tests.
Because of these problems, clinicians use the Widal test extensively to diagnose typhoid in both public and private sectors in India.
About Widal test:
- Widal test is a serology blood test that helps detect typhoid or enteric fever in the body.
- This test was first conducted in 1896 by Georges Ferdinand Widal and was named after him.
- It is an advanced way to check for antibodies that your body makes against the salmonella bacteria that cause typhoid fever.
- It looks for O and H antibodies in a patient’s sample blood (serum).
- As with other infections, our immune system produces antibodies in the blood against the bacteria, causing enteric fever. The Widal test rapidly detects and quantifies these antibodies.
- Widal is a point-of-care test and doesn’t need special skills or infrastructure.
- Developed in the late 1800s, it is no longer used in many countries because of its flaws.
Shortcomings of the Widal test:
- False positives:
- The Widal test can produce false-positive results due to cross reactivity with other non typhoid diseases: Malaria, Dengue, miliary tuberculosis, endocarditis, chronic liver disease, brucellosis, etc. in typhoid endemic regions, and thereby increase the Positivity rate of typhoid fever.
- Widal test can produce false positive results in people who have got vaccinated against typhoid fever or who have had a previous infection with a related bacterium.
- In areas with high and continuous typhoid burden, certain levels of antibodies against the bacteria may already be present in the blood.
- False negatives: The test can also give false-negative results in case the patient is in carrier state , particularly if conducted during the early stages of the disease or if the patient has received antibiotics prior to testing. This can lead to missed diagnosis.
- Subjectivity in interpretation: The Widal test requires the interpretation of antibody titers by a trained healthcare professional. The interpretation can be subjective, and results may vary between individuals.
- Variable sensitivity and specificity: The sensitivity and specificity of the Widal test can vary depending on the test methodology, the region where it is performed, and other factors.
- Correct diagnosis and appropriate treatment of enteric fever are important because serious complications, like severe intestinal bleeding or perforation, can develop within a few weeks if the disease is mismanaged. False negatives can thus delay diagnosis and lead to fatal outcomes.
Consequences of the Widal test’s use:
- Because of the Widal test’s propensity for erroneous results, the actual burden of typhoid in India remains unknown.
- Financial woes of the patients:
- Patients in many States have also reported being charged Rs 500 to Rs 4,000 per dose of antibiotic injections by local healthcare providers following a typhoid diagnosis based on a single Widal test.
- Patients in both urban and rural areas have reported selling assets to receive these antibiotics.
- Some strains of Salmonella are also resistant to multiple drugs.
- Continued irrational use of the Widal test, facilitating unnecessary use of antibiotics, will only make it more and more difficult to control this preventable disease.
Way Forward:
- There is a need to discover better point-of-care tests that can replace the Widal test.
- Doctors should rely on established guidelines to diagnose and treat patients effectively.
- They should also consider regional antibiotic data for choosing the best treatment options.
- These options should be coupled with ensuring adequate and safe food and water and functional sanitation to address the disease’s root cause.
- We need better surveillance to stay on top of the AMR caused by the overuse of the Widal test.
- The Indian Council for Medical Research publishes an annual report highlighting the typhoid bacteria’s resistance patterns.
- Finally, as typhoid also has symptom-free carriers, constant environmental vigilance and data-sharing are imperative for fighting against the disease.
