Tuberculosis overview

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Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Tuberculosis from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Children

HIV Coinfection

Diagnosis

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

Chest X Ray

CT

MRI

Echocardiography or Ultrasound

Other Imaging Findings

Other Diagnostic Studies

Treatment

Medical Therapy

Special Conditions
Drug-resistant

Surgery

Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]; João André Alves Silva, M.D. [3]; Ammu Susheela, M.D. [4]

Overview

Tuberculosis (abbreviated as TB or Tuberculosis) is a common infectious disease caused by Mycobacterium tuberculosis. Tuberculosis most commonly involves the lungs as the organism thrives in high oxygen environments, but it can also cause disease in the central nervous system, the lymphatic system, the circulatory system, the genitourinary system, bones, joints and even the skin. Over one-third of the world's population has been exposed to M. tuberculosis, and new infections occur at a rate of one per second. Not all individuals exposed to the bacterium develop clinically overt tuberculosis infection; in fact, asymptomatic, latent TB infection discovered by screening is more common. Approximately, one in ten latent infections progresses to active (symptomatic) TB disease, which, if left untreated, carries mortality rates of up to 50%. Symptoms include shortness of breath, hemoptysis, fever, chills, night sweats, and weight loss. Several treatment regimens are available for the latent and active forms of TB. Classically, a prolonged course of 6-9 months of a single agent (rifampin or isoniazid) is administered to patients with latent TB, while a more aggressive course that consists of 4 major anti-tuberculous agents (rifampin, isoniazid, ethambutol, pyrazinamide) is reserved for patients with active disease.

Historical Perspective

Classification

TB Classification System

  • As per CDC (Centers of Disease Control and Prevention), the clinical classification system for TB used in the United States is based on the pathogenesis of the disease.
  • This classification system provides clinicians the opportunity to keep an eye on the development of TB in their patients.
  • Health care providers should follow with state and local laws and regulations requiring the reporting of TB disease.
  • All persons with Class 3 or Class 5 TB should be reported directly to the local or state health department.
  • A patient should not have a Class 5 classification for more than 3 months.
Class Type Description
0 *No TB exposure
*Not infected
*No history of TB exposure and no evidence of M. tuberculosis infection or disease
*Negative reaction to TST or IGRA
1 *TB exposure
*No evidence of infection
*History of exposure to M. tuberculosis
*Negative reaction to TST (Tuberculin skin tests) or IGRA (an interferon gamma release assay blood test) (given at least 8 to 10 weeks after exposure)
2 *TB infection
*No TB disease
*Positive reaction to TST or IGRA
*Negative bacteriological studies (smear and cultures)
*No bacteriological or radiographic evidence of active TB disease
3 *TB clinically active *Positive culture for M. tuberculosis OR
*Positive reaction to TST or IGRA, plus clinical, bacteriological, or radiographic evidence of current active TB
4 *Previous TB disease (not clinically active) *May have past medical history of TB disease
*Abnormal but stable radiographic findings
*Positive reaction to the TST or IGRA
*Negative bacteriologic studies (smear and cultures)
*No clinical or radiographic evidence of current active TB disease
5 *TB suspected *Signs and symptoms of active TB disease, but medical evaluation not complete

Pathophysiology

Causes

Epidemiology and Demographics

Risk Factors

Screening

Natural history, complications and prognosis

Diagnosis

History and Symptoms

Physical Examination

Laboratory findings

Electrocardiogram

Chest X-Ray

CT

MRI

Echocardiography or Ultrasound

Other Imaging findings

Other Diagnostic Studies

Treatment

Medical Therapy

Special conditions

  • Medical therapy for tuberculosis in special conditions include HIV co-infection and extra pulmonary manifestations.
  • Different approaches are taken for patients taking ART and those who do not take ART.
  • Although WHO recommends the same drug regimen for pulmonary and extrapulmonary manifestations, various stages of skeletal tuberculosis are managed differently.
  • For patients with renal or liver diseases, the first line of drugs are substituted with second-line drugs to prevent complications.

Drug-resistant

Children

Surgery

Primary Prevention

Secondary Prevention

Cost effectiveness of therapy

Future or investigational therapy

References

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