Tuberculosis

(Redirected from Tb)

Background

  • Over 1/3 of world's population is infected

Infection Types

  • Primary Infection
    • Usually contained by body via formation of tubercles
    • Hematogenous spread limited to areas with high O2 or blood flow (apical lung, vertebrae)
      • PPD positive
  • Reactivation Infection
    • More common in immunocompromised patients (AIDS, malignancy, DM, immunosupressive medications)
  • Miliary Tuberculosis
    • Disseminated tuberculosis
    • Looks like millet seeds
    • Seen in patients with comorbid AIDS
      • Check HIV in patients suspected of TB
    • PPD is positive in only 50% of cases

Special Populations

  • AIDS
    • TB is 200-500x more common in AIDS population than general population
    • CD4 count
      • Increased risk when <500
      • Determines the clinical and radiographic presentations of TB
  • Pediatric
    • More likely to progress early to active disease
      • Presentation more commonly that of primary TB
    • >5yr - classic symptoms
    • <5yr - miliary TB, meningitis, cervical lymphadenitis, pneumonia that does not respond to usual antibiotics
    • Children are usually not infectious due to their weak cough

Tuberculin Skin Test

Used for population screening, but not for rule-out in patients with concern for active disease

Reaction considered positive in following situations:

  • >5 mm
    • HIV positive
    • Close contact with active TB patient
    • Nodular or fibrotic changes on CXR
    • Immunosuppressed (TNF-alpha inhibitor, chemo, organ transplant)
  • >10 mm
    • Children < 4 yrs old
    • Healthcare/lab/prison employees and residents
    • Co-morbid conditions (dialysis, DM, blood/head/neck/lung malignancy, IV drug users)
    • People from high prevalence areas
  • >15 mm
    • Persons with no known risk factors for TB

Clinical Features

Tuberculous lymphadenopathy

Primary Tuberculosis

  • Usually asymptomatic (only identified by positive PPD/quantiferon gold)
  • May be rapidly progressive and fatal in immunocompromised patients
  • Tuberculous pleural effusion may occur if subpleural node ruptures into the pleura
    • Pleuritic chest pain
    • Exudative fluid
      • Organisms may not be visible on acid-fast staining (need pleural biopsy)

Reactivation Tuberculosis

Differential Diagnosis

HIV associated conditions

Evaluation

CXR of miliary TB
Miliary TB neonate born to mother with active TB
Bilateral pulmonary tuberculosis
Tuberculous vertebral osteomyelitis (Pott's Disease)

CXR

  • Primary infection
    • Infiltrates in any area of the lung
    • Isolated hilar or mediastinal adenopathy may be only finding
  • Reactivation infection
    • cavitary/noncavitary lesions in upper lobe or superior segment of lower lobe
  • Latent infection
    • Upper lobe or hilar nodules and fibrotic lesions
    • Ghon foci, areas of scarring, calcification
  • Miliary TB
    • Looks like millet seeds on CXR
  • Immunocompromised patients less likely to have classic lesions and may have normal CXR

PCR Sputum Assay

  • Rapidly detects TB in sputum specimens (as well as rifampin resistance)
  • Use to rule-out patients for active TB
  • Need two sputum specimens (expectorated or induced) at least 8 hours apart (including at least one early morning specimen)

Management

Active TB

Latent TB

  • Isoniazid x 9 months
  • Consider treatment for:
    • Recent conversion to PPD-positive
    • close contact with active TB
    • immunocompromised patients (or plan to start immunosuppressive medications)
  • New vaccine has demonstrated effectiveness (50%) in preventing progression to active TB[2]. However, this is not yet widely available and further research is needed.

Disposition

Discharge

  • Otherwise healthy
    • Contact public health services before discharge
      • Instructions for home isolation and follow up at appropriate clinic to receive meds
    • Do not start TB meds in ED unless specifically instructed by public health

Admit

  • Ill-appearing
  • Diagnosis is uncertain
  • Patient is treatment non-adherent

References

  1. Gutteridge, David L MD, MPH, Egan, Daniel J. MD. The HIV-Infected Adult Patient in The Emergency Department: The Changing Landscape of the Disease. Emergency Medicine Practice: An Evidence-Based Approach to Emergency Medicine. Vol 18, Num 2. Feb 2016.
  2. Final analysis of a trial of M72/AS01E vaccine to prevent tuberculosis Tait DR, Hatherill M, Van Der Meeren O, et al. N Engl J Med. 2019;381(25):2429-2439.