Flashcards in Clinical TB Deck (35):
Is tuberculosis (TB) considered both a "disease of poverty" and a disease associated with HIV?
YES, however wealthy individuals can also contract the disease like Nelson Mandela, Eleanor Roosevelt, Ringo Star...
Are the number of TB cases overall decreasing?
What are the risk factors for TB?
- immune suppression (HIV, cancer, steroids, transplant)
- occupational (health care workers, prison guards)
- substance abuse (alcohol)
- malnutrition (gastrectomy, bypass...)
- poor medical care
What is Mycobacterium tuberculosis?
- acid- fast, slow growing, aerobic bacillus with a highly lipid cell wall that can affect many organ systems.
- mycolic acid in the cell wall allows us to stain it using the Ziehl Neelsen stain
What does TB do to the lung?
- causes granulomatous inflammation with caseous necrosis= cheese like exudates.
- will see multinucleated giant cells (Langhans cells) with aggregations of epithelioid cells and a collar of lymphocytes within the alveoli of the lung.
How is TB transmitted?
- aerosolized droplet (1-5 micrometers) transmission (cough, sneezing, speaking, singing).
- less than 10 droplets are required to cause infection and one sneeze carries at least 3000 droplets.
Do most people who come into contact with a TB patient contract the disease?
NO (70% do not become infected)
If you do get infect, and have a positive PPD, what is the chance that you will never have active TB?
What is the body's immune response to TB?
- droplets are engulfed by lung dendritic cells and macrophages, which activate lymphocytes, which secrete cytokines, recruiting more macrophages, and this is what leads to granuloma formation (macrophages surrounded by lymphocytes).
- the granuloma is the protective response that contains the organisms by creating a low O2 and low pH environment.
What are the signs and symptoms of TB?
weight loss (anorexia), fever/chills/night sweats, fatigue, cough greater than 3 weeks, hemoptysis, and chest pain.
What can you find of physical examination?
- cachexia (weakness and wasting), fever, lymphadenopathy, hepatosplenomegaly, tachycardia, friction rub, hypoxia, rales, decreased breath sounds, dullness to percussion, or egophony.
What are the extrapulmonary sites of TB?
- CNS (meningits)
- lymphatics (scrofula of the neck)
- pleura (TB pleurisy)
- disseminated (miliary TB)
- bones and joints of spine (Pott's disease)
What can TB mimic?
asthma, influenza, drug abuse, pneumonia, ARDS, lung neoplasms, aspergillosis, bronchiolitis, asbestosis, pneumothorax...
What should be your initial workup?
- tuberculin skin test/interferon-gamma release blood test
- serum sputum smears (AFB; acid-fast bacillus)= less than 24 hours :)
- opt-out HIV test
What is a NAA smear?
nucleic acid amplification test to determine the makeup of what acid-fast organism you are dealing with. Takes 2 days.
What other tests can you do?
- bronchoscopy, biopsy, high-performance liquid chromatography, pleural effusion analysis, CSF analysis...
What is the purified protein derivative (PPD) test/ Mantoux method or called tuberculin skin test (TST)?
protein extracts of Mycobacterium that are injected under the skin to test for T cell mediated/delayed-type hypersensitivity reaction (meaning you've been exposed before if it reacts).
- positive= feel for edges of the welt and measure between these edges. Usually greater than 10 mm is positive, except for special circumstances.
What are the disadvantages of a PPD/TST?
- requires follow-up
- false-positives (previously BCG-vaccinated individuals or other Mycobacterial infections).
- false negatives (anergic or immune suppressed, bc you need an active immune system to respond to this).
What is the interferon-gamma (quanti-FERON gold) test?
newer, better test, the uses a patient's blood sample, separates out the lymphocytes, and then exposes the lymphocytes to tuberculosis antigen.
- no reader bias, results within 24 hrs, no BCG reaction, and no amnestic response)
*Note: this doesn't separate out active TB from past infection.
What CXR findings will you find with TB?
- airspace consolidation
- volume loss
- pleural effusions (ipsilateral)
- linear opacities
- Ghon/Ranke complexes= parenchymal scar with calcium within it + calcified hilar lymph node.
What segments of the lung does TB affect?
- primary infection= middle and lower lobes
- reactivation infection=posterior and apices, and spares the anterior portions.
What is miliary TB?
hematogenous dissemination of the disease, appears as a micro-nodular pattern throughout the lungs.
*** How do we make the diagnosis of TB?
- get respiratory secretions, look under the microscope, Zehl Neelsen AFB positivity (red stained acid-fast structures) and then grow it out on culture.
What is the law when diagnosing someone with TB?
notify the state within 5 work days
*** How do we treat active pulmonary TB?
- First line= Isoniazid (INH), Rifampin (RIF), Pyrazinamide, and Ethambutol.
- Second line= fluoroquinolones (levofloxacin...)
**** What TB drugs attack the cell wall and what are their side effects?
- Isoniazid= inhibits mycolic acid cell wall synthesis, but can cause LIVER toxicity.
- Ethambutol= inhibits cell wall synthesis of arabinogalactan.
**** How does Pyrazinamide work against TB and what are the side effects?
inhibits the cell membrane and disrupts ATP synthesis, but can cause HYPERURICEMIA.
**** How does Rifampin work and what are the side effects?
inhibits RNA synthesis. Will cause harmless orange/red urine, and can decrease effectiveness of women taking ORAL CONTRACEPTIVES.
**** Do you use all 4 drugs (isoniazid, rifampin, pyrazinamide, and athambutol) for first 2 months of TB treatment?
YES and then continue with just isoniazid and rifampin for 4-7 additional months for a total therapy of 6-9 months!
What program will ensure pts comply to their treatment if you are concerned they will not?
DOTS (Directly Observed Treatment Short course), which involves a state run center physically observing the pts take their medication.
How do you manage a latent TB infected pt (non-contagious, positive TST, negative CXR, and asymptomatic)?
give isoniazid for 9 months.
What are the recommendations for preventative therapy for PPD-positive persons?
- all persons less than 35 years old.
- only those over 35 who are: recent converter, close contact of active case, HIV positive, or IV drug user.
*this is because side effects for these older pts must be taken into account and you don't want to give it to a pt who doesn't need it.
What must you do for all pts taking Isoniazid?
follow liver function tests (LFTs ) and make sure they REFRAIN from ALCOHOL.
Do multi-drug resistant TB strains exist to both isoniazid and rifampin?
YES, then use streptomycin or Levofloxacin (fluoroquinolone).