Survey Reveals 39% of TB Cases in Tamil Nadu are Asymptomatic

Survey Reveals 39% of TB Cases in Tamil Nadu are Asymptomatic

A recent cross-sectional TB prevalence survey conducted in Tamil Nadu from February 2021 to July 2022 uncovered that 39% of detected TB cases had no symptoms, underscoring the prevalence of subclinical TB. The survey involved over 130,000 participants, with 125,870 undergoing both symptom screening and chest X-ray examination.

Key findings include:

1.       High Rate of Asymptomatic TB: Out of 244 microbiologically confirmed TB cases, 39% were asymptomatic, highlighting the critical need for chest X-rays in detecting subclinical TB.

2.      Diagnostic Tool Effectiveness: Chest X-rays revealed abnormalities in 92.6% of cases. Molecular tests (CBNAAT) accurately detected 91.8% of cases, while smear microscopy detected only 50.40%.

3.      Recommendations for Improvement: The study suggests prioritizing chest X-rays and expanding molecular tests for earlier detection and to cut the transmission chain. Current practices often miss subclinical TB cases.

4.      Implications for TB Management: Utilizing chest X-rays and molecular diagnostics could significantly enhance TB detection rates. The findings indicate that subclinical TB can play a major role in TB transmission, even in the absence of symptoms like coughing.

Global Perspective

This phenomenon is not unique to Tamil Nadu. A meta-analysis published in the journal Lancet Infectious Diseases in March 2024 examined surveys from several high TB-burden countries, revealing that 27.7% of people with TB had no symptoms. The study emphasized that a significant portion of those with pulmonary TB do not cough, which is traditionally associated with higher infectiousness. These asymptomatic cases, also referred to as subclinical TB, can still contribute substantially to TB transmission.

Furthermore, a 2021 paper in the American Journal of Respiratory and Critical Care Medicine highlighted that people with subclinical TB could maintain high bacillary loads typically linked to transmission, even without coughing. This reinforces the importance of using chest X-rays and molecular diagnostics globally to improve TB detection and management strategies.