The document discusses guidelines for tuberculosis (TB) testing and treatment. It provides criteria for positive TB test results based on induration size and risk factors. It notes that interferon gamma release assays (IGRAs) are at least as sensitive as the tuberculin skin test (TST) for detecting TB infection. Both tests detect exposure to TB but cannot differentiate between active disease and latent infection. IGRAs are preferred in those with BCG vaccination or nontuberculous mycobacterium infection history. Treatment options for latent TB infection include various combinations of isoniazid and rifampin administered for 3-9 months, depending on medications and patient risk factors such as HIV status.

1. 1) Classification of the Tuberculin Skin Test Reaction
Induration:5 mm or more Induration:10 mm or more Induration:15 mm or more
HIV + or persons immune
suppressed for other reasons
(i.e. prednisone 15 mg or more
for 1 month of takingTNF-alpha
inhibitor
Recent immigrants (< 5 years)
from high risk prevalence
countries
Any person, includingthose
without known risk factors for
TB
Recent contactof person with
activeTB
IVDU
Persons with fibrotic changes
on CXR consistentwith prior TB
Residents and employees of
high-risk congregatesettings
Organ transplantpatients Mycobacteriology laboratory
personnel
2) The IGRA tests are at leastas sensitiveas theTST, though considered to be more specific
3) Both the TST and IGRA detect exposure to MTB but do NOT tell the difference between activeTB disease
versus latent TB infection
4) An IGRA (interferon gamma releaseassay) is a wholeblood test that detects either the number of WBC
releasinginterferon gamma or the amount of interferon gamma released by WBC
5) IGRA arepreferred in those with poor followup, prior BCG vaccine,or those with history of NTM (except
M. marinumor M. kansasaii)
6) In general, only a TST or IGRA is needed, though in very high risk patients or very low risk patients itis
reasonableto obtain both. If orderingboth, there is evidence of a “boosting” effect to the IGRA, so obtain
the TST first,then at the time of TST readingobtain the IGRA
7) Treatment of LTBI:
a) Rifampin x 4 months
b) INH + rifampin x 3 months
c) INH + rifapentine,weekly, 3 months, via DOT
d) INH x 9 months
-If your patient is HIV + and on ART, utilizeINH and avoid the rifamycins given drug-drug interactions
8) 5 mm of induration is considered positivein thosewith RA (note that RA itself has been implicated in TB)
9) 1-2 weeks of treatment is needed prior to startingthe TNF-alpha inhibitor
10) Lymph node involvement and pleural disease
11) Exudative, lymphocytic.The rule of thumb is a lymphocyte: PMN ratio > 0.75
12) ADA in the pleural fluid can beused. If the ADA is <40, the pleural effusion is mostsurely NOT from TB.
Note that there aretwo types of ADA – ADA 1 and ADA 2. ADA 1 can be elevated in bacterial empyema,
parapneumonic effusion,lungcancer, lymphoma, and mesothelioma, while elevated ADA-2 is usually only
elevated in TB.