Tuberculosis Flashcards
Method of TB transmission?
Airborne droplets
When we do a ZN smear for TB, what do the number of acid-fast bacilli present represent?
The infectiousness of the patient, and how likely they are to be ill
What is the gold standard for TB diagnosis?
Culture method
What is the most sensitive and fastest culture method?
Selective broth culture, 7-20 days
How do we do a Tuberculin skin test, (TST)
intradermaly inject 0.1ml of PPD into the skin of the forearm
What can cause a false positive in TST?
Previous BCG vaccination
So for TST, we measure the induration within 48-72 hours, this gives us 3 levels of positive results, what’s the first?
=>5mm, highest risk of disease development
What is =>10mm of induration mean?
Increased probability of recent infection, like from immigrants
What does an induration of =>15mm mean?
Low risk of TB
When do we do Two-step TST testing?
In healthcare workers given their occupational risks
What are the advantages of IGRAs, interferon gamma release assays?
They don’t react with BCG vaccinations, and are practitioner dependent, we don’t need the patient to come back
What’s the disadvantage of IGRAs?
They are expensive
What’s the goal of screening for Latent TB?
To identify people at increased risk of developing active TB disease
Who does the CDC recommend targeted testing for?
People with recent exposure or at high risk for disease reactivation
What methods are used for Latent TB testing?
TST and IGRAs
