Clinical Manual for Management of the HIV-Infected ... - myCME.com

Latent Tuberculosis
Background
Latent (or inactive) tuberculosis (TB) infection occurs
when an individual has dormant Mycobacterium
tuberculosis organisms and no active disease, and can be
diagnosed by a tuberculin skin test (TST). Persons with
HIV or AIDS and latent TB infection (LTBI) have a
much higher risk of developing active TB (estimated
at 10% per year) than does the general population
(estimated at 10% in a lifetime). The risk of developing
active TB can be reduced dramatically with treatment
of LTBI. Hence, identifying and treating HIV-infected
persons for LTBI is a high priority. Treatment of LTBI
not only reduces the risk of disease for the individual,
but also reduces the risk of further TB transmission
should the HIV/TB-coinfected person develop active
pulmonary TB. Standard treatment with isoniazid
(INH) is effective and safe.
Issues of concern regarding the treatment of LTBI
among HIV-infected persons include the following:
♦
♦
♦
♦
Excluding active pulmonary or extrapulmonary TB
disease before treatment with INH alone
Assessing the risk of latent infection with drugresistant
TB
Avoiding or managing drug interactions if rifampin
or rifabutin regimens are used
Exercising great caution in the use of rifampin/
rifabutin and pyrazinamide combinations for LTBI
treatment
S: Subjective
HIV-infected persons who have no symptoms of active
TB (ie, afebrile, stable weight, no cough) and who
have not been treated previously for active or latent
TB are eligible for LTBI treatment. When patients do
have symptoms that could represent active TB, active
TB must be evaluated and ruled out by appropriate
diagnostic methods before initiating treatment (see
“Assessment” below).
Persons who have had bacillus Calmette-Guérin (BCG)
vaccine should be evaluated in the same way as those
who have never had BCG. Immigrants from many
countries will have had childhood vaccination.
Section 2—Health Maintenance and Disease Prevention | 2–39
History
Health care providers should ask about a history of
potential exposure to TB, because this might indicate
infection with drug-resistant TB. Such risk might occur
when there is knowledge of a source patient or when
the exposure occurred in a setting with known drug
resistance or a location with ongoing TB transmission
where others remain at risk for exposure).
O: Objective
Physical Exam
Current U.S. guidelines strongly recommend
performing a TST in newly diagnosed HIV-infected
persons. Repeat testing is recommended for those
whose CD4 lymphocyte count increases from low
numbers to counts of >200 cells/µL, and annual testing
is suggested for those who initially test negative. The
TST is administered as an intradermal injection of
0.1 mL (5 tuberculin units TUs) of purified protein
derivative (PPD), which raises a wheal in the skin. This
also is known as the Mantoux test. Multiple-puncture
tests such as tine tests and the use of other strengths
of PPD are considered unreliable. Anergy testing is
not recommended routinely because a randomized
controlled study in HIV-positive patients in the United
States failed to show an advantage to treating anergic,
tuberculin-negative persons.
PPD tests are not designed for reading by the patient;
a trained health care worker must measure the area of
induration (not erythema) 48-72 hours after the test is
placed. Induration of 5 mm or more is a positive result
in HIV-infected persons, other immunosuppressed
persons, anyone with recent TB exposure, and anyone
with fibrosis on chest x-ray consistent with previousTB.
For HIV-uninfected health care workers, 10 mm of
induration is positive; in various other populations,
either 10 mm or 15 mm of induration may be
considered positive. Many large HIV clinics find it
challenging to get their patients to return for the PPD
reading. One randomized study found that offering
incentives (eg, a fast-food coupon) plus counseling was
more effective than counseling alone in obtaining return
visits for PPD readings.