Tuberculosis Diagnosis and Prevention

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Tuberculosis (TB) remains the leading cause of death from an infectious disease among adults worldwide, with over 10 million people becoming newly infected each year. Despite the challenges, advances in diagnosis and treatment hold promise for changing the trajectory of TB control, although the disease remains a serious global public health threat.

Advances in Diagnosis

Rapid molecular testing and whole-genome sequencing have become crucial tools in diagnosing TB, detecting drug resistance, and improving our understanding of transmission. Molecular tests such as the Xpert MTB/RIF assay have revolutionized TB diagnostics by enabling quick detection of Mycobacterium tuberculosis (M. tuberculosis) and rifampicin resistance. The Xpert MTB/RIF Ultra, a more sensitive version, offers results comparable to traditional culture methods but in a fraction of the time. Another significant development is the urinary lipoarabinomannan (LAM) test, which has shown clear mortality benefits, especially in HIV-positive individuals with a low CD4 count.

However, diagnostic challenges remain. No simple, point-of-care test is available to definitively diagnose TB, and tests such as the tuberculin skin test (TST) and interferon-gamma release assays (IGRA), though used for latent TB detection, have limited accuracy in differentiating between latent infection and active disease. Chest X-rays, particularly with computer-aided detection, are also making a comeback as a triage tool in certain settings.

Drug-Resistant Tuberculosis

While the treatment for drug-susceptible TB has not changed significantly, major strides have been made in managing drug-resistant TB. In 2018, the World Health Organization (WHO) recommended all-oral regimens for drug-resistant TB, a significant shift from earlier treatments that relied on injectable agents. New drugs like bedaquiline and delamanid, along with repurposed drugs like linezolid and clofazimine, are at the forefront of these changes.

Shorter regimens for drug-resistant TB, lasting 9 to 12 months compared to the previous 18 to 24 months, are also becoming more common. Despite concerns about potential side effects like QT prolongation, these regimens are generally well-tolerated and have shown cost-effectiveness compared to older, injectable-based therapies. However, the high cost of newer drugs, such as bedaquiline, remains a barrier to wider access.

Challenges in TB Control

Despite the availability of more effective diagnostic and treatment tools, TB remains a disease that disproportionately affects impoverished populations. Socioeconomic factors such as poor living conditions, indoor air pollution, and overcrowding are key drivers of TB transmission. Studies, including one from Peru, have shown that modifiable risk factors like poor housing conditions can significantly predict the likelihood of TB infection.

People living in poverty are also at greater risk of reinfection, further exacerbating the cycle of TB and poverty. In low-burden countries, improvements in living conditions have led to substantial reductions in TB incidence, highlighting the need for a comprehensive approach that includes both medical and socioeconomic interventions.

Prevention and the Role of Vaccines

The Bacillus Calmette-Guérin (BCG) vaccine, which has been in use for nearly a century, continues to provide protection against severe forms of TB in children. However, its efficacy in preventing pulmonary TB in adults is limited. New vaccine candidates are being developed, with some showing promise in preventing the progression of latent TB to active disease. Additionally, WHO has recommended several regimens for treating latent TB infection, with rifampicin and rifapentine-based regimens proving as effective as longer isoniazid-based therapies.

The Way Forward

Although diagnostic and treatment tools for TB have advanced, success in controlling the disease will depend on more than just medical innovations. The quality of TB care must improve, focusing on patient-centered approaches that provide socioeconomic support alongside medical treatment. Conditional cash transfers and programs aimed at reducing catastrophic costs for TB patients have shown promise in improving outcomes.

Renewed political will, better access to high-quality care, and addressing the social determinants of TB are essential to curbing the global burden of the disease. Without these measures, TB, especially drug-resistant strains, will continue to pose a significant threat to global health.

Source: 

Furin, J., Cox, H., & Pai, M. (2019). Tuberculosis. Lancet (London, England), 393(10181), 1642–1656.

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