TB Flashcards
How is TB transmitted?
Respiratory droplets (coughing, sneezing, vocalizing) rapidly evaporate and bacilli circulate airborne
When after initiation of treatment is the patient no longer contagious?
After 2 weeks of 3 or 4 drug chemotherapy or if initially was AFB +ve then after 3 negative AFBs
In what situations is extrapulmonary TB contagious?
- Oral cavity lesions
Open skin lesions
What are the 4 Dannenberg stages of pathogenesis of TB?
Stage 1: alveolar macrophages ingest inhaled bacillus
Stage 2: bacili replicate in macrophage and lyse it attracting more macrophages which then are infected
Stage 3: infected macrophages are activated by CD4 T helper cells and cytotoxic CD8 cells arrive. all work together to create caseating granuloma: at this point infection can progress or become latent
Stage 4: reactivation or reinfection
List symptoms of pulmonary tuberculosis.
Cough Weight loss Chills Fatigue Anorexia Tactile fever Chest pain Night sweats Dyspnea Hemoptysis
List 7 populations at increased risk for TB:
- Foreign born in africa, asia, s. america
- HIV
- contacts of known case
- medically inderserved, low income
- long-term care facility residents
- IVDU
- occupational exposure
- groups with local prevalence
List RF for reactivation
HIV Recent TB (within 2 yrs) CXR shows prev untreated TB IVDU DM silicosis immunosuppresion (steroids, immunosuppresants) Head/neck ca heme dz ESRD intestinal bypass chronic malabsorption low body weight
List 6 complications of pulmonary TB.
PTX empyema hemoptysis pericarditis superinfection airway TB endobronchial spread
What is a Rasmussen’s aneurysm?
Psuedoaneurysm that results when a TB lesion or cavity that erodes into a pulmonary artery – Potential for massive (and fatal) hemoptyis
What % of patients with active TB will have negative PPD skin testing?
~20%
A normal CXR is reported to be a useful screening (high NPV) test for pulmonary TB. What is the false negative rates of a normal CXR?
- Immunocompetant: FN LT 1%
HIV: FN 7 – 15%
List 4 CXR findings for TB.
- Upper lobe cavitary lesions
- Bilateral upper lobe infiltrates : highly likely to be TB if see on CXR!!
- Consolidation with enlarged hilar or mediastinal nodes
- Milliary TB
- Moderate to large pleural effusion
- Well circumscribed nodular coin lesions (Tuberculonmas)
- Calcified nodular scar: Gohn focus
Provide a DDx for cavitary lesions on CXR:
- TB
- Other Infections:
o Klebsiella pneumoniae
o Staphylococcus aureus
o M. avium complex (in HIV pts) - Cancer:
o Bronchogenic Carcinoma - Other:
o Aspiration pneumonia
Pulmonary infarction secondary to PE
List criteria for a positive tuberculin skin test.
- > 5mm: immunosuppressed, close contacts
- > 10mm: any TB RF
15mm: all other people
List sites of extrapulmonary TB.
- Lymphatic
- Pleural
- Bone or joint
- GI
- Menigeal
- Peritoneal
Other (skin, heart, pericardium, thyroid, mastoid cells, sclera, adrenal glands
List a differential for scrofula.
- Lymphoma
- Metastatic cancer
- Fungal disease
- Cat-scratch disease
- Sarcoid
- Toxoplasmosis
- Reactive adenitis
- Bacterial adenitis
- Tularemia
- Yersenia pestis
What are the most commonly involved bone and joints in EPTB?
- Spine (Potts disease) from paravertebral nodes (50-70%)
- Hip, knee (15-20%)
- Other less common: ankle, elbow, wrists, shoulders
List features of CSF in TB meningitis.
- WBC# 0 – 1500
- Predominance of lympohocytes (May be predominantltly PMNs)
- Increased protein
Decreased glucose
What is recommended treatment for TB meningititis?
- 4 drug regime: INH, pyrazinamide, rifampin, steroids
- Prednisone 60 – 80mg daily tapered over 4 – 6 weeks
- +/- VP shunt for hydrocephalus
What is the most emergent presentation of TB?
- Massive hemoptysis = 600mL/24 hours
List fist line TB drugs and adult and child doses.
First Line (RRRIPE)
- Rifampin
- Rifabutin
- Rifapentine
- Isoniazid
- Pyrazinamide
- Ethambutol
List major side effects of the four most common TB drugs.
- INH
o MOA:
§ Creates functional deficiency of pyridoxine
§ Results in GABA depletion à INH induced Sz!!
o Toxicity:
§ Acute toxicity: refractory seizures, AGMA, coma
§ Chronic toxicity: Hepatotoxicity, peripheral neuropathy
o Antidote:
§ Pyridoxine used in INH therapy as prevention of neuropathy
§ Acute INH induced Sz à pyridoxine 5g (70mg/kg) bolus - RIF
o Discolouration of body fluid - PZA
o Hepatotoxicy
o Polyarthralgias - ETH
o Retrobulbar neuritis and colourblindness
List risk factors for drug-resistant TB (Box-135-5).
· Patient o HIV +ve o Failure to respond or adhere to prior treatment o Unsuccessful treatment o Poor gastric absorption o Cavitary lung lesion · Close contact with source case · Socio-economic o Immigration from area with drug resistance o IVDU o Homeless o Imprisonment
What are considerations when treating TB in pregnancy?
- TREAT! Rifampin, isoniazid, and ethambutol are NOT teratogenic.
Give pyridoxine
List guidelines for the management after accidental exposure to TB at work in the ED (Box-135-6):
- TB skin test early for baseline to assess for prior TB exposure
- Re-test in 3 months to see if there is conversion
- If Positive, check for evidence active disease CXR. If abnormal treat
- If no active disease, follow the below guidelines:
