Tuberculosis

Tuberculosis 150 150 Tony Guo

Tuberculosis

 

  • Infectious disease caused by Mycobacterium tuberculosis
  • Lungs most commonly infected
  • 1/3 of world’s population has TB
  • Leading cause of death in patients with HIV/AIDs
  • Prevalence is decreasing in the United States

 

Risk factors

  • Homeless
  • Residents of inner-city neighborhoods
  • Foreign-born persons
  • Living or working in institutions (includes health care workers)
  • IV injecting drug users
  • Poverty, poor access to health care
  • Immunosuppression

 

Multidrug-Resistant Tuberculosis (MDR-TB)

  • Resistance to 2 of the most potent first-line anti-TB drugs
  • Extensively drug-resistant TB (XDR-TB) resistant to any fluoroquinolone plus any injectable antibiotic
  • Several causes for resistance occur
    • Incorrect prescribing
    • Lack of case management
    • Nonadherence 

 

Etiology and pathophysiology

  • Spread via airborne particles
  • Can be suspended in air for minutes to hours
  • Transmission requires close, frequent, or prolonged exposure
  • NOT spread by touching, sharing food utensils, kissing, or other physical contact
  • Once causative organisms gains entrance, particles lodge in bronchioles and alveoli
  • Local inflammatory reaction occurs
    • Ghon lesion or focus – represents a calcified TB granuloma
    • Infection walled off and further spread stopped
  • Only 5% to 10% will develop active TB
  • Aerophilic (oxygen-loving) – causes affinity for lungs
  • Infection can spread via lymphatics and grow in other organs as well
    • Cerebral cortex
    • Spine 
    • Epiphyses of the bone
    • Adrenal glands

Classification

  • Classes
    • 0 = No TB exposure
      • No TB exposure, not infected (no history of exposure, negative tuberculin skin test)
    • 1 = Exposure, no infection
      • TB exposure, no evidence of infection (history of exposure, negative tuberculin skin test)
    • 2 = Latent TB, no disease
      • TB infection without disease (significant reaction to tuberculin skin test, negative bacteriologic studies, no x-ray findings compatible with TB, no clinical evidence of TB
    • 3 = TB, clinically active
      • TB infection with clinically active disease (positive bacteriologic studies or both a significant reaction to tuberculin skin test and clinical or x-ray evidence of current disease)
    • 4 = TB, not clinically active
      • No current disease (history of previous episode of TB or abnormal, stable x-ray findings in a person with a significant reaction to tuberculin skin test. Negative bacteriologic studies if done. No clinical or x-ray evidence of current disease)
    • 5 = TB suspected
      • TB suspect (diagnosis pending). Individual should not be in this classification for >3 months
  • Primary  infection
    • When bacteria are isoniazidaled
  • Latent TB infection (LTBI)
    • Infected but no active disease
  • Active TB disease
    • Primary TB
    • Reactivation TB (post-primary)

Clinical manifestations

  • LTBI – asymptomatic
    • Cannot spread TB bacteria to others
    • Usually has a skin test or blood test result indicating TB infection
    • Has a normal chest x-ray and a negative sputum smear
    • Needs treatment for latent TB infection to prevent active TB disease
  • Pulmonary TB
    • Takes 2-3 weeks to develop symptoms
    • Initial dry cough that becomes productive
    • Constitutional symptoms (fatigue, malaise, anorexia, weight loss, low-grade fever, night sweats)
    • Dyspnea and hemoptysis late symptoms
  • Cough becomes frequent
    • Hemoptysis is not common and is usually associated with advanced disease
    • Dyspnea is unusual
  • Can also present more acutely
    • High fever
    • Chills, generalized flulike symptoms
    • Pleuritic pain
    • Productive cough
    • Crackles and/or adventitious breath sounds
  • Extrapulmonary TB manifestations dependent on organs infected
  • Immunosuppressed people and older adults are less likely to have fever and other signs of an infection
    • Carefully investigate respiratory problems in HIV patients
      • Rule out opportunistic diseases
    • A change in cognitive function may be the only initial sign of TB in an older person

Complications

  • Miliary TB
    • Large numbers of organisms spread via the bloodstream to distant organs
    • Fatal if untreated
    • Manifestations progress slowly and vary depending on which organs are infected
    • Fever, cough, and lymphadenopathy occur
    • Can include hepatomegaly and splenomegaly
  • Pleural TB
    • Chest pain, fever, cough, and a unilateral pleural effusion are common
    • Pleural effusion
      • Bacteria in pleural space cause inflammation.
      • Pleural exudates of protein-rich fluid
    • Empyema
      • Large numbers of tubercular organisms in pleural space
  • TB pneumonia
    • Large amounts of bacilli discharged from granulomas into lung or lymph nodes
    • Manifests as bacterial pneumonia
  • Other organ development
    • Spinal destruction
    • Bacterial meningitis
    • Peritonitis

 

Diagnostic Studies

  • Tuberculin skin test (TST) 
    • AKA: Mantoux test
    • Uses purified protein derivative (PPD) injected intradermally
    • Assess for induration in 48 – 72 hours
    • Presence of induration (not redness) at injection site indicates development of antibodies secondary to exposure to TB
    • Positive if ≥15 mm induration in low-risk individuals
    • Response decrease in immunocompromised patients
    • Reactions ≥5 mm considered positive
    • A waning immune response can cause false negative results
    • Repeating TST may boost reaction
    • Two-step testing recommended for health care workers getting repeated testing and those with decreased response to allergens
    • Two-step testing ensures future positive results accurately interpreted
  • Interferon-γ gamma release assays (IGRAs) 
    • Detects  T-cells in response to Mycobacterium tuberculosis
    • Includes QuantiFERON-TB and T-SPOT.TB tests 
    • Rapid results
    • Several advantages over TST but more expensive
  • Chest x-ray
    • Cannot make diagnosis solely on x-ray
    • May appear normal in a patient with TB
    • Upper lobe infiltrates, cavitary infiltrates, lymph node involvement, and pleural and/or pericardial effusion suggest TB
  • Bacteriologic studies
    • Required for diagnosis
    • Consecutive sputum samples  obtained on 3 different days
    • Stained sputum smears examined for AFB
    • Culture results can take up to 8 weeks
    • Can also examine samples from other suspected TB sites

Interprofessional care

  • Hospitalization not necessary for most patients
  • Infectious for first 2 weeks after starting treatment if sputum +
  • Drug therapy used to prevent or treat active disease
  • Need to monitor compliance

Drug therapy

  • Active disease
    • Treatment is aggressive  
    • Two phases of treatment
      • Initial (8 weeks)
      • Continuation (18 weeks)
    • Four-drug regimen
      • Isoniazid
      • Rifampin (Rifadin)
      • Pyrazinamide 
      • Ethambutol
    • Patients should be taught about side effects and when to seek medical attention
    • Liver function should be monitored
    • Alternatives are available for those who develop a toxic reaction to primary drugs
  • Directly observed therapy (DOT)
    • Noncompliance is major factor in multidrug resistance and treatment failures
    • Requires watching patient swallow drugs
    • Preferred  strategy to ensure adherence 
    • May be administered by public health nurses at clinic site
  • Latent TB infection
    • Usually treated with Isoniazid for 6 to 9 months
    • HIV patients should take Isoniazid for 9 months
    • Alternative  3-month regimen of Isoniazid and rifapentine OR 4 months of rifampin
  • Vaccine
    • Bacille-Calmette-Guérin (BCG) vaccine to prevent TB is currently in use in many parts of world
    • In United States, not recommended except for very select individuals
    • Can result in positive PPD reaction

 

Nursing Assessment

  • History
  • Physical symptoms
    • Productive cough
    • Night sweats
    • Afternoon temperature elevation
    • Weight loss
    • Pleuritic chest pain
    • Crackles over apices of lungs
  • Sputum collection

Nursing diagnoses

  • Ineffective breathing pattern related to decreased lung capacity
  • Ineffective airway clearance related to increased secretions, fatigue, and decreased lung capacity

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