TYPHOID
1. Context
Because of the Widal test’s propensity for erroneous results, the actual burden of typhoid in India remains obfuscated. A lack of awareness of the proper time at which to collect a blood sample, along with a lack of standardisation of kits and poor quality-control, compound the problem
2. What is Typhoid?
- Typhoid fever is a bacterial infection caused by Salmonella enterica serotype Typhi bacteria. It's transmitted through contaminated food or water, or by close contact with someone who's infected.
- Symptoms typically include sustained high fever, weakness, stomach pains, headache, loss of appetite, and sometimes a rash. If untreated, typhoid fever can be fatal, but it's treatable with antibiotics.
- Vaccines are also available for prevention, particularly for those traveling to regions where typhoid is prevalent. Proper sanitation and hygiene practices are crucial in preventing its spread
- Typhoid fever spreads through tainted food and water, caused by bacteria like Salmonella typhi. Also known as enteric fever, it manifests with symptoms such as high fever, abdominal discomfort, weakness, and additional issues like nausea, vomiting, diarrhea, or constipation, as well as a rash.
- Some individuals, known as carriers, may not show symptoms but can excrete the bacteria in their faeces for months or even years.
| These symptoms resemble those of other illnesses such as malaria, dengue, flu, and typhus, each requiring different treatment approaches. If not treated, typhoid can become life-threatening. According to the World Health Organization, approximately 9 million people worldwide are diagnosed with typhoid annually, with 110,000 deaths attributed to it. A small study from 2023 found the incidence to be between 576 and 1173 cases per 100,000 child-years in urban areas and 35 per 100,000 child-years in rural Pune |
3. How is typhoid fever diagnosed?
- The primary method for diagnosing typhoid involves a comprehensive medical history review, physical examination, and isolating the bacteria from a patient's blood or bone marrow for cultivation in a laboratory setting. While stool and urine samples can also be used for this purpose, they typically exhibit lower sensitivity.
- However, conducting culture tests in smaller clinical facilities poses practical challenges. Culturing is time-consuming and demands specialized skills and resources.
- Additionally, prior antibiotic treatment may influence culture results, a common concern due to widespread antibiotic usage in India.
- While certain PCR-based molecular techniques offer improved accuracy, their adoption is hindered by cost, infrastructure requirements, skilled personnel, and the inability to obtain live bacteria for further analysis.
- In India, clinicians frequently rely on the Widal test for typhoid diagnosis across both public and private healthcare sectors.
- This test identifies and measures antibodies produced by the immune system in response to the Salmonella bacteria, facilitating rapid diagnosis at the point of care without necessitating specialized skills or infrastructure.
- Although developed in the late 1800s by a French physician, the Widal test has fallen out of favour in many countries due to its inherent limitations, which are exacerbated by its widespread use in India
4. Why is Widal inappropriate?
- A single positive Widal test result doesn't definitively indicate the presence of a typhoid infection, and a negative result doesn't conclusively rule out the disease.
- To accurately diagnose an active infection, clinicians typically need to test at least two serum samples collected 7-14 days apart to detect changes in antibody concentrations. However, obtaining two samples is often impractical and time-consuming.
- Furthermore, in regions where typhoid is prevalent, individuals may already have certain levels of antibodies against the bacteria in their blood.
- Without knowledge of the baseline cutoff, interpreting the test results accurately is challenging. Additionally, different manufacturers of the test specify varying cutoff values in their kit manuals, further complicating interpretation.
- Another issue with the Widal test is that the reagents used to detect antibodies can cross-react with antibodies produced against infections caused by other bacteria, viruses, or parasites.
- This cross-reactivity can lead to false positive results, particularly in individuals who have received the typhoid vaccine or have been exposed to other infections. Prior antibiotic treatment can also impact antibody levels, potentially resulting in false negative results.
- Accurate diagnosis and prompt treatment of enteric fever are crucial because serious complications, such as severe intestinal bleeding or perforation, can arise within a few weeks if the disease is not managed effectively. False negatives from diagnostic tests can therefore delay diagnosis and contribute to fatal outcomes
5. Consequences of the test’s use
- Due to the Widal test's tendency to yield inaccurate outcomes, the true extent of typhoid fever in India remains obscured. Challenges such as a lack of awareness regarding optimal blood sample collection timing, variability in kit standardization, and inadequate quality control exacerbate this issue.
- Moreover, the cost of a single test typically amounts to a few hundred rupees. Patients across various states have reported exorbitant charges ranging from Rs 500 to Rs 4,000 per dose for antibiotic injections administered by local healthcare providers upon a typhoid diagnosis based solely on a single Widal test. Both urban and rural patients have resorted to selling assets to afford these antibiotics.
- The indiscriminate use of antibiotics is a primary driver of antimicrobial resistance (AMR), a global health concern. Bacteria can transfer AMR traits across strains and species, transcending geographical boundaries.
- Consequently, the proliferation of AMR poses a threat worldwide. Additionally, certain Salmonella strains exhibit resistance to multiple drugs.
- Continued unjustified reliance on the Widal test, which fosters unnecessary antibiotic administration, will exacerbate the challenge of controlling this preventable disease while compounding financial burdens for afflicted patients
6. Way Forward
Enhancing accessibility to more advanced diagnostic examinations could offer a solution to this issue. Conducting blood or bone marrow cultures frequently proves impractical due to the absence of laboratory facilities in many regions of the country. Implementing a 'hub and spoke' model could be advantageous, wherein sample collection sites are established at decentralized locations, while district hospitals and medical colleges serve as central hubs for sample processing. Additionally, these centralized facilities could double as research centres, generating data on regional prevalence and susceptibility patterns
Source: The Hindu
