Tuberculosis- Prager

Question 1

Definition of Tuberculosis

Answer 1

Illness caused by chronic inflammation secondary to infection by Mycobacterium tuberculosis and characterized by creation of granulomas in affected organs and immunologic cellular response. Predominantly affects the lungs. About 60% of untreated die.

Question 2

Properties of the mycobacterium tuberculosis bacillus

Answer 2

Small, rod-shaped, aerobic, bacillus. Cell wall contains high concentration of lipids, resulting in resistance to standard staining, decolorizing-“acid fast”, and resistant to digestion by macrophages. doesn’t show up on gram stain making treatment evaluation more difficult.

Question 3

Classification of population wrt TB

Answer 3

Level 0: no exposure, no infection

Level 1: exposure, no evidence of infection (negative skin test, most healthcare workers)

Level 2: Evidence of infection but no disease (positive skin test, sequestered TB, 1/3 of world’s population)

Level 3: Infection with disease (60% die if untreated, 40% have remission into level 2)

Question 4

Factors for risk of infection of TB

Answer 4

1. Number of organisms in the sputum
2. Pulmonary cavities contain the most organisms (as opposed to other granulomas)
3. Frequency of cough

(Not contagious after 2 weeks of therapy)

Exposure with prolonged close contact with aerosole.

Question 5

Pathogenesis of TB

Answer 5

Inhalation

Primary infection: mild inflammatory reaction (T-cell activation, ingestion by macrophages, migration to lymph nodes, hematogenous spread of organisms, healing of initial infection and Ghon complex formation (calcified focus and regional node). Most likely in the lower and mid zones with hilar adenopathy. No containment in immunosuppressed.

Secondary infection: reactivation of dormant focus. Weight loss, low grade fever, night sweats, persistent, dry cough; occasional hemoptysis but often delayed diagnosis. Usually in higher oxygen sections of lung-upper lobes.

Question 6

Diagnosis of TB

Answer 6

History and PE

CXR (non-homogenous reticulo-nodular infiltrates, cavities, scars)

Sputum (may have to enduce coughing), fiberoptic bronchoscopy (fast but insensitive, sputum more sensitive)

AFB smear, washing, tissue (must do 3 then culture, insensitive and nonspecific)

Culture (more definitive but takes 6-8 weeks)

PCR-rapid but expensive

Question 7

Pleural TB

Answer 7

Young adults with primary infection, adults with reactivation, acute or indolent. Caused by pleural hypersensitivity reaction to rupture of subpleural caseous focus into pleura. Exudative effusion, lymphocytic. AFB negative, biopsy is best bet (for granulomas).

Treat patients with effusion and positive PPD. High risk for active TB.

Question 8

Miliary TB

Answer 8

Caused by hematogenous dissemination of MTB, usually with immunocompromise. In children often after primary infection. Lesions in nonpulmonary organs. Fuzzy CXR, millet seed dots throughout. Diagnosis with tissue biopsy and culture of other organs. Fatal without treatment (100%). May not cause cough.

Question 9

What is measured immunologically in PPD and QuentiFERON?

Answer 9

IFNgamma. IL8 and TNFalpha also released.

Question 10

What is QuantiFERON?

Answer 10

In vitro blood test for TB. Add antigens to patient’s serum. Measure IFN-gamma that will be realeased if memory T-cells recognize TB antigens implying prior infection/latent TB infection (LTBI).

Better for BCG vaccination. Preferred for every except children under 5. Better specificity.

Question 11

Who is at highest risk for developing active TB?

Answer 11

 HIV infected persons
 Recent (within 2 years) skin test converters
 Close contacts of active cases
 Recent arrivals (within 5 years) from high prevalence countries
 Patients with prior untreated tuberculosis

• Patients with certain medical conditions

 receiving immunosuppression
 end-stage renal disease
 diabetes mellitus
 Carcinoma of the head and neck
 Status-post gastrectomy
 silicosis

Question 12

Therapy of TB

Answer 12

 chemotherapy is the only effective treatment
for tuberculosis
 single-drug therapy for active disease is
associated with a substantial relapse rate and
with the development of isolates resistant to
the initial drug
 patients with active disease should receive at
least three drugs as initial therapy
 never add a single drug to a failing regimen
 compliance with therapy is the responsibility
of the treating physician as well as the
patient

NEVER TREAT ACTIVE TB WITH A SINGLE DRUG

2 months of RIPE (rifampin, isoniazid, pyrazinamide, ethambutol) followed by 4 months of isoniazid and rifampin

DOTS is best.

Question 13

Components of DOT programs from basic to most comprehensive

Answer 13

1. provision of medication
2. nursing services for
   providing medicine
   assessing for side effects
   patient education
3. outreach workers
   deliver medicine outside program
   track missing patients
4. provision of incentives/enablers
   funds for transportation
   food
   bonus payments
5. social services
   housing
   substance abuse counseling