Tuberculosis Flashcards
what is the risk of starting a anti TNF alpha inhibitor?
reactivates TB
How to test for active pulmonary TB?
induced sputum tested for AFB.
Quantiferon Gold will be positive for life? True/false
true. so not helpful for determining if someone has active dx.
treatment options for latent TB infection
isoniazide and rifapentine weekly for 3 months under DOT (not recommended for HIV pt)
isoniazid monotherapy for 6-9 months (give them pyridoxine (Vitamin B6) to prevent neuropathy from isoniazid)
rifampin for 4 months.
No need for baseline or monthly monotring of LFTs unless at risk for hepatotoxicity (HIV infection, chronic Hep B or C or ETOH use, pregnancy or other concurrent hepatotoxic drugs or underlying liver dx)
pyridoxine is also known as
B6 vitamin supplement. Give this in pts on isoniazid to prevent peripheral neuropathy. Also higher risk for B6 deficiency are those with DM2, uremia, ETOH, malnutrition and HIV, pregnancy and epilepsy
Major side effects of isoniazid therapy
vitamin b6 deficiency
neuropathy
hepatitis - stop drinking ETOH and check LFTs every 3 months
When to stop isoniazid due to LFT side effects
check LFTs q3months and stop if serum transaminase levels are >3 times the normal limit in symptomatic pts and >5 times normal limit in asymptomatic pts
who needs to get sputum samples for acid fast stain?
pts with concern for TB and they have respiratory symptoms OR chest XR symptoms concerning for active TB
Tuberculin skin test (TST) is positive at >5mm when they are
close contacts of known TB case.
10 mm cut off is used for recent immigrants from endemic areas, IVDA, residents, employees of high risk settings and those at risk for TB reactivation (glucosteroids and leukemia and ESRD)
what does a positive TST mean?
it means exposure and doesn’t need to be repeated. close contacts who have negative initial TST should have repeat TST done at 8-12 weeks.
pts to treat if PPD or TST induration is >5mm
HIV positive pts recent contacts of known TB case nodular or fibrotic changes on CXR consistent with previously healed TB organ transplant recipient or other immunosuppressed pt
pts to treat if PPD or TST induration is >10mm
recent immigrants from endemic areas, IVDA, residents, employees of high risk settings (prisons, SNF, hosptials and homeless shelters) and those at risk for TB reactivation (DM2, glucosteroids and leukemia and ESRD, chronic malabsorption syndromes) kids<4 yrs and those exposed to adults in high risk categories
pts to treat if PPD or TST induration is >15mm
all the above plus healthy individuals
those who have been exposed to the highly infectious pulmonary TB should get a
TST within a week of exposure. If negative it doesn’t mean they don’t have it; it means they need repeat TST in 8-12 weeks.
is there a window period from infection/exposure to detectable PPD skin test?
yes. it’s about 2-12 weeks and so CDC recommend retesting exposed individuals again with a repeat TST test 8-152 weeks after exposure for those who have a negative TST initially
what to do after someone has a positive TST?
need a CXR and symptom review to clarify if they have active pulmonary TB
how long does it take for a interferon gamma release assay to turn positive after exposure
there’s also a window period and it takes about 4-6 weeks
are interferon gamma release assays (IGRAs) affected by the BCG vaccine?
no they are not affected by this. TST can be affected by BCG vaccine.
positive test TST criteria?
>10 mm increase within a 2 year period
Prophylaxis of TB in HIV positive pts
side effects of rifampin
hyperuricemia
discolored body fluids
hepatitis
rifampin and rifapentine also can cause drug interactions
clinical manifestations of a TB infection:
fever,
weight loss,
productive cough (blood tinged sometimes)
anorexia, malaise
pleuritic chest pain
Latent TB is defined as:
positive TST or IGRA with no clinical or radiographic manifestation of active TB
When do we prefer to do a IGRA (quantiferon gold) test over a TST?
when pt is <5 years old
older pts who are likely to have M tb
low to intermediate risk of dx progression
history of BCG (bacillus Calmette Guerin) vaccination
or unlikely to return to have TST result read.
in which cases or clinical scenarios are IGRA better than using a TST to tell if they have TB?
BCG (bacillus Calmette Guerin) vaccination and non tuberculous mycobacterium infection.
IGRAs have less cross reactivity and sensitization with BCG (bacillus Calmette Guerin) vaccination whereas TST will show a bump or induration
IGRAS have less cross reactivity and sensitization by non tuberculous mycobacterium
how to diagnose some with active TB infection?
All suspected people must get AFB smear microscopy
Testing three samples is recommended because can have both false negative and false positive
Need to get expectorated sputum (preferred over BAL) and needs 5-10 ml _at least 8 hrs apar_t with one early morning specimen.
Gold standard is - culture of MTB - liquid or solid cultures which return in 2-4 weeks (as opposed to traditional 8-10 weeks)
If sputum smear is positive for AFB, then need to get NAAT or nucleic acid amplification testing - which detects PCR of TB in sputum. PPV of NAAT on a smear positive sputum is 95%
Gold standard of active TB infection
Gold standard = culture of MTB - liquid or solid cultures which return in 2-4 weeks (as opposed to traditional 8-10 weeks)
importance of getting NAAT testing for TB and how it all fits in to diagnosis of TB.
three expectorated sputums 8 hrs apart with one early morning sputum for AFB smear microscopy
If sputum smear is positive for AFB, then need to get NAAT or nucleic acid amplification testing - which detects PCR of TB in sputum. PPV of NAAT on a smear positive sputum is 95%
If negative smear, NAAT can be positive in 65% of cases
NOTE a negative NAAT doesn’t exclude TB - can confirm presence of TB in 50-80% of time on AFB negative smear, culture positive specimens.
NAAT also can help detect for rifampin resistance.
gold standard diagnosis : culture of AFB.
histopathology of TB is
caseating granulomas which are suggestive but not exclusive to or diagnostic of TB.
can get blood cultures of TB.
Pregnant women who have latent TB should get
should delay or defer therapy until after delivery unless the pt is at high risk for developing active infection due to immunocompromise (HIV)
Treatment of active TB infection
1st line agents: isoniazid, rifampin, pyrazinamide, ethambutol
- from multidrug resistant and extensively drug resistant TB
needs 6-9 months of treatment (4 drugs given daily for 2 months then can get isoniazid plus rifampin daily for 4 months)
Direct observed thearpy is needed
recheck sputum samples at 1 month and 2 months to look for efficacy.
what must be checked prior to starting TB treatment for active TB infection?
check CBC, LFTs, hepatitis serology and clinical assessment.
Drug resistant TB is:
isoniazid resistant TB- isoniazid, rifampin, ethambutol can be given 6 months but some experts recommend adding a fluoroquinolone
isoniazid and rifampin resistant MDR-TB (multi drug resistant) - FIVE drug regimen depneding on isolate susceptbility for 4 months followed by four drug regimen for 12-18 months
HIV and TB
TREAT TB infection first before HIV….can layer in ART to avoid IRIS.
ART should be started within 2 weeks (after starting TB meds) with CD4<50
start ART by 8 to 12 weeks (after starting TB meds) with CD4 >50 or more
exception is HIV positive pts with TB meningitis then ART should not be started during first 8 weeks of TB therapy regardless of CD4 count due to increased morbidity because of IRIS.
when are active TB pts safe and no longer contagious (ok to remove the airborne precautions)
- needs to be on appropriate TB meds for 2 weeks
- clinical improvement of signs and symptoms
- 3 negative sputum smears collectived at least 8 hours apart with one being an early morning specimen
Pts with negative smears are less contagious even if they still have infection.
what to do with someone who is on chemotherapy and getting immunosuppressants and has been living with a someone who has acute TB infection (with cavitary lesion)?
High risk pts for TB infection are those that include (duration of space of contact with infected indvidual as well as degree of symtpoms especially the presence of cavitation of X-Ray).
These include HIV pts, chemotherapy pts, immunosuppressed (TNF alpha agents)
get a TST in those who haven’t gotten BCG vaccine. If they got BCG vaccine get interferon gamma release assay.
In the meantime treat with isoniazid and pyridoxine
there is a window period of 8-10 weeks after exposure where TST and quantiferon is negative. Negative test at 8 and 10 weeks ok to stop treatment.
