Interventions for Tuberculosis Control and Elimination 2002

might be expected, therefore, that prevention of development of tuberculosis
would also delay onset of AIDS among HIV infected patients (figure
79). There is, however, as yet little epidemiological evidence that this
is the case. 883
A series of controlled clinical trials has been undertaken in various
settings to evaluate the efficacy of isoniazid (and other compounds) compared
to placebo in protecting HIV-infected individuals against tuberculosis
(figure 80).
The first study of this kind was conducted in Port-au-Prince, Haiti. 884
The efficacy of 12 months of isoniazid compared to placebo was ascertained.
The protection among persons with five or more millimeters of
induration to a tuberculin skin test was 83%. The population was small,
however, and the confidence intervals were consequently wide. An additional
finding was a significant delay in onset of HIV disease in the isoniazid
group compared to those receiving placebo. Survival analysis also
demonstrated significant protection against AIDS-defining illnesses and
AIDS-attributable death among tuberculin-positive, but not among tuberculin-negative,
patients.
In Lusaka, Zambia, HIV-positive individuals were randomly assigned
to receive twice-weekly isoniazid for six months or placebo and a third arm
Infection
with M. tbc
Preventive
therapy
Tuberculosis TNF - �
HIV replication
Increased
immunosuppression
132
AIDS
Granuloma
formation
Figure 79. Schematic presentation of the impact of tuberculosis on TNF-α production
and HIV replication, and prevention of the chain of events with preventive
therapy.