Bonus Material-34_CHEST_ Board Review 2024 TB-LTBI FINAL DAH

Pdf Summary

This comprehensive review by Dr. Doreen Addrizzo-Harris focuses on tuberculosis (TB), covering epidemiology, pathogenesis, diagnosis, treatment, and latent TB infection (LTBI).<br /><br />TB is caused by Mycobacterium tuberculosis, transmitted via airborne droplet nuclei, influenced by patient infectiousness, environment, and exposure duration. Approximately 35% of household contacts get infected, yet most do not develop disease due to immune containment—resulting in latent TB infection (LTBI), which is asymptomatic and non-infectious.<br /><br />Diagnosis involves clinical suspicion, symptoms (fever, cough, night sweats), risk factor evaluation (HIV, immunosuppression), radiologic imaging, and microbiologic tests. Sputum smear microscopy detects acid-fast bacilli but has limited sensitivity; culture remains the gold standard but is slow. Nucleic Acid Amplification Tests (NAATs) like GeneXpert MTB/RIF rapidly detect TB and rifampin resistance, aiding early diagnosis.<br /><br />Radiographically, post-primary/reactivation TB typically shows apical cavitary lesions, while primary TB displays lower lobe infiltrates, lymphadenopathy, or pleural effusions. Smear-negative TB can still transmit infection.<br /><br />Treatment of active drug-susceptible TB uses multidrug therapy—initially isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), and ethambutol—to prevent resistance. Standard duration is six months but extended to nine months in cases like intolerance to PZA, extensive cavitary disease, or delayed sputum conversion. Drug-resistant TB (MDR and XDR forms) require expert-guided regimens including newer agents like bedaquiline.<br /><br />LTBI testing targets high-risk groups, especially contacts, foreign-born individuals from high TB prevalence countries, and immunocompromised patients (HIV, TNF-alpha blockers). TST and Interferon Gamma Release Assays (IGRAs) are screening tools; IGRAs are preferred in BCG-vaccinated individuals due to higher specificity.<br /><br />Treatment regimens for LTBI include rifampin for 4 months, INH plus rifampin for 3 months, or weekly INH-rifapentine for 12 doses, with alternatives for pregnancy and drug intolerance. Active TB must be excluded before LTBI treatment to prevent resistance.<br /><br />Overall, TB control requires focused diagnosis, appropriate multidrug therapy, and targeted LTBI screening and treatment to prevent progression and transmission, especially amid rising drug resistance and global disparities.

Meta Tag

Concept Tuberculosis

Concept Latent Tuberculosis Infection

Concept Active Tuberculosis

Concept Drug-resistant tuberculosis

Concept Diagnosis

Keywords

tuberculosis

Mycobacterium tuberculosis

latent TB infection

diagnosis

sputum culture

GeneXpert MTB/RIF

drug-resistant TB

isoniazid

rifampin

interferon gamma release assay

Tuberculosis

Latent Tuberculosis Infection

Active Tuberculosis

Drug-resistant tuberculosis

Diagnosis