Recent research from a state-wide tuberculosis (TB) prevalence survey conducted in Tamil Nadu, India, has revealed critical insights into screening and diagnostic methods for the infectious disease. A total of 130,932 individuals were screened using chest X-ray (CXR) and a symptom checklist to detect TB, which continues to be a major public health issue globally. The findings from this study highlight the mixed effectiveness of commonly used screening methods in identifying TB cases among a large population.
TB remains a significant health challenge worldwide, with approximately 7.5 million new cases diagnosed in 2022, of which 83% were pulmonary TB. Recognizing the need for effective testing, the World Health Organization (WHO) recommends systematic screenings for populations in regions with TB prevalence exceeding 0.5%. The Tamil Nadu TB prevalence survey aimed to evaluate the efficacy of various screening and diagnostic tests deployed within the community, aiding in the quest to improve TB control strategies.
The survey's results were notable: among the 130,932 individuals examined, 130,914 underwent symptom screening and 125,870 completed both symptom screening and chest X-ray examinations. The research identified that a cough lasting more than two weeks, often regarded as a key symptom of TB, exhibited a sensitivity of 41.6%. However, its specificity was limited at 72.8%, signaling a considerable number of false positives that could arise when relying solely on symptom assessment.
On the other hand, the abnormal chest X-ray displayed a higher sensitivity of 86.4% and a lower specificity of 42.12%. When these two screening methods were combined, the sensitivity for identifying potential TB cases increased significantly to 97.9%, though with a drastically reduced specificity of just 4.9%. This indicates that while the combination of CXR and symptom screening is highly sensitive, it may also lead to a larger number of individuals being inaccurately identified as having TB, necessitating further testing.
The diagnostic tests applied during the survey included the Xpert/MTB RIF test, smear microscopy, and culture techniques. The Xpert/MTB RIF test performed in the reference laboratory demonstrated the highest sensitivity at 96.55%, outperforming smear microscopy which showed an impressive specificity of 99.7%. Notably, the mobile van Xpert/MTB RIF testing also recorded a high specificity at 99.3%, underscoring its effectiveness as a field diagnostic tool.
Given the additional context of TB diagnostics, the study's authors argue that symptom screening, followed by chest X-rays and rapid molecular tests, constitutes a robust algorithm for TB detection in high-burden regions. This diagnostic approach not only improves case detection rates but also enhances the clarity of treatment pathways for health care providers.
Overall, the findings from this extensive survey will assist TB program managers and public health officials in defining better diagnostic algorithms for active case finding and prevalence surveys, aiming to bridge gaps in TB detection and treatment. While traditional diagnostic methods like smear microscopy have their place, the advent of rapid molecular diagnostics represents a crucial advancement toward more reliable TB management. With further refinement in procedures and increased implementation of advanced technologies such as portable X-ray machines and AI reporting, the future of TB diagnostics looks promising.
The study, conducted under the auspices of Tamil Nadu's health authorities and supported by the National Health Mission, aims to fortify TB elimination efforts in India, highlighting the essential need for ongoing research and adaptation to enhance TB detection and management strategies in line with current global health directives.
