Seattle Treatment Education Project: STEP Perspective - Volume 4, Number 3 - October 1992
Lori Panther, M.D.

TB in HIV-infected people tends to occur at relatively high CD4 counts (300 to 400). HIV-infected people exposed to TB in the past are 24 times more likely to develop active disease than HIV-negative individuals previously exposed to TB (called reactivation TB). Clinical symptoms are sometimes difficult to attribute to possible TB infection, so diagnosis is sometimes missed: between 5 and 9 percent of TB in people with AIDS is diagnosed after death (Chaisson, USA, Session 136). TB in HIV-infected people often occurs outside the lung (called extrapulmonary TB), and side effects from TB medication are more likely to occur in this population.

TB in HIV-infected individuals is one opportunistic infection that does not need to be treated indefinitely after initial therapy (Schuermann, Germany, PoB3096). Currently recommended regimens advise therapy for 12 months. In HIV-positive people who test positive for prior exposure to TB, treatment with isoniazid (INH) for 12 months will substantially decrease the risk of developing active TB (Selwyn, USA, previous data; Wadhawan, Zambia, TuB0536).

Because of inaccurate diagnosis, poor compliance with medication, and inadequate individual follow-up, two problems have emerged with respect to TB in the HIV-positive population: (1) the incidence of TB is continuing to increase, and (2) inadequate treatment of TB that was once sensitive to many anti-TB drugs has resulted in the emergence of TB strains resistant to many of the drugs commonly used to treat the infection.

Multidrug-resistant Tuberculosis. MDRTB was first reported in New York City and Florida. Greater than 90 percent of MDRTB occurs in HIV-positive people, and mortality from MDRTB is greater than 80 percent. In 1991, 20 percent of all TB cases reported to the New York City Health Department were MDRTB (Chaisson, USA, Session 136). Study of the problem at the University of Miami showed that infection with MDRTB in HIV-positive people was 11 times more likely in those with AIDS than in those with asymptomatic HIV infection. Clinically, it is much more aggressive and involves both the lung and sites outside the lung in a single individual (pulmonary and extrapulmonary TB). The 50 percent mortality ratio from MDRTB in HIV-positive people is two to three months. Seventy-five percent of people with MDRTB do not clear their infection despite therapy (Fischl, USA, TuB0534).

The problem of MDRTB has raised important questions regarding treatment for this disease. Unfortunately, there is no immediate method to distinguish drug-sensitive TB from MDRTB. Sometimes several weeks are needed to generate drug sensitivity data. Currently, the standard of care is to begin treating the individual with the common drugs used for treatment of sensitive TB. If the individual does not clinically respond after five days of therapy, serious consideration should be given to switching to a treatment regimen which would be more effective for MDRTB (Mullen, USA, TuB0535).
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