Bonus Material-34_CHEST_ Board Review 2025 TB-LTBI FINAL DAH

Pdf Summary

This CHEST Board Review by Dr. Doreen Addrizzo-Harris provides a comprehensive overview of tuberculosis (TB) and latent tuberculosis infection (LTBI), covering epidemiology, pathogenesis, diagnosis, and treatment.<br /><br />TB is caused by Mycobacterium tuberculosis and transmits via airborne droplets, with infection risk influenced by patient infectiousness, environment, and exposure duration. Most exposed do not become infected; about 35% of household contacts acquire infection. Latent TB infection occurs when bacteria remain dormant yet viable; these individuals are asymptomatic and non-infectious. Diagnosis of LTBI traditionally used the tuberculin skin test (TST), now supplemented by interferon gamma release assays (IGRAs) like QuantiFERON and T-spot which offer better specificity, especially in BCG-vaccinated persons.<br /><br />Active TB develops in 5-10% with untreated LTBI, risk elevated notably with HIV or immunosuppression. Drug resistance definitions include multidrug-resistant TB (MDR-TB) resistant to isoniazid and rifampin, with extensively drug-resistant TB (XDR-TB) adding fluoroquinolone and injectable resistance. Drug-resistant TB is a rising global threat exacerbated by underdiagnosis and underreporting.<br /><br />Diagnosis relies on clinical suspicion, symptoms (fever, cough, weight loss), radiographic findings (upper lobe cavitary lesions for reactivation disease), and microbiology. Acid-fast bacilli (AFB) smears have limited sensitivity; culture remains gold standard but is slow. Nucleic acid amplification tests (NAAT) including GeneXpert MTB/RIF detect M. tuberculosis and rifampin resistance rapidly but do not replace cultures.<br /><br />Treatment for drug-susceptible TB includes an initial 2-month regimen of isoniazid, rifampin, pyrazinamide, and ethambutol, followed by continuation with isoniazid and rifampin, typically for a total of six months; extensions apply in certain cases. MDR-TB requires individualized, expert-guided regimens including newer agents like bedaquiline.<br /><br />For LTBI, targeted testing is recommended for high-risk groups (contacts, foreign-born from high prevalence countries, immunosuppressed). Treatment regimens include rifampin for 4 months, isoniazid plus rifampin for 3 months, or weekly isoniazid plus rifapentine for 12 doses. Pregnancy and HIV require special considerations.<br /><br />In summary, TB control demands high clinical vigilance, appropriate diagnostic testing, and tailored treatment strategies to manage active disease and prevent LTBI progression, especially amidst growing drug resistance.

Meta Tag

Concept Tuberculosis

Concept Latent Tuberculosis Infection

Concept Mycobacterium tuberculosis Infection

Concept Reactivation Disease

Concept Human Immunodeficiency Virus Infection

Keywords

tuberculosis

latent tuberculosis infection

Mycobacterium tuberculosis

interferon gamma release assay

tuberculin skin test

multidrug-resistant TB

nucleic acid amplification test

isoniazid rifampin pyrazinamide ethambutol

bedaquiline

rifapentine

Tuberculosis

Latent Tuberculosis Infection

Mycobacterium tuberculosis Infection

Reactivation Disease

Human Immunodeficiency Virus Infection