Subclinical TB

Why in news?

In a recent meeting at Health Ministry, the challenges in detecting subclinical TB cases and ensuring effective treatment was highlighted. 

What is Subclinical TB?

• Subclinical TB- It refers to TB cases where the patient is infected with tuberculosis but does not show the typical symptoms associated with the disease.
• Causal agent - It is caused by viable Mycobacterium tuberculosis bacteria.
• Traits – It includes cases that are culture-positive but lack typical TB symptoms such as-
  • No persistent cough.
  • No cough at all.
  • No TB-suggestive symptoms (cough, chest pain, fever, night sweats, or weight loss).

Tuberculosis (TB) remains a major public health challenge despite the UN's resolution to end TB by 2035. In 2022, there were 7.5 million new TB cases and 1.3 million deaths globally.

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• Spread - The national TB prevalence survey (2019-2021) found that 42.6% of detected TB cases were subclinical, which would have been missed without a chest X-ray.
  • Tamil Nadu's TB survey reported 39% subclinical TB cases.
• It constitutes a significant proportion of TB cases, with up to 82.7% showing no persistent cough.
• Silent Infection Source - It can lead to diagnostic delays and lead to continued transmission.
  • 29% of those without persistent cough & 23% without any cough are still smear-positive, indicating potential for transmission.

What are the major challenges of Subclinical TB?

• Vulnerability - High-burden states in India are likely to have a significant prevalence of subclinical TB.
  • High-burden countries showing a median of 50% subclinical TB cases.
• Asymptomatic nature- It is difficult to identify and diagnose through routine screenings.
• Delayed diagnosis- It leads to longer diagnostic delays, allowing the disease to progress and increasing the risk of transmission.
• Detection gaps- Traditional diagnostic methods, like sputum tests and symptom-based screening, may miss subclinical cases, especially in areas with limited healthcare resources.
• Scaling challenges- Implementing widespread chest X-ray screening requires mobile units and regular community screenings.

India's goal is to increase molecular testing from 30% to 100% within 12 months to improve TB diagnosis and reduce morbidity and mortality.

• Underreporting- For every TB case notified, there are potentially two undetected cases with culture-positive TB, leading to slow progress in reducing TB incidence.
• Patient compliance- Convincing asymptomatic individuals to begin and complete a six-month treatment regimen is challenging, with higher dropout rates despite potentially better outcomes.
• Incomplete treatment may lead to higher risks of drug resistance and treatment failure.

What lies ahead?

• Implementing AI-based chest X-ray screening to detect TB more efficiently.
• Ensuring consistent drug supply and scaling up human resources.
• Implement active case-finding initiatives using mobile vans, computer-aided radiology, and rapid molecular tests.
• Update the definition of TB-suggestive symptoms to include a broader range of indicators (e.g., any cough, weight loss, night sweats) to improve early detection.
• Educate communities about the risks of subclinical TB and the importance of early detection and treatment.
• Utilize digital adherence tools to ensure patients with subclinical TB complete their treatment regimens.
• Conduct more research to develop and validate shorter, more effective treatment regimens specifically tailored for subclinical TB cases.

Vietnam has successfully reduced TB prevalence by 50% in some areas through symptom-agnostic screening (X-rays and molecular tests) of the entire population annually.

References

1. The Hindu | Subclinical TB
2. The Lancet | Subclinical TB