Interventions for Tuberculosis Control and Elimination 2002

tionally considered to belong to groups at risk of tuberculous infection.
Only nine cases of tuberculosis occurred in the entire cohort of more than
500 patients during a follow-up period of 30 months following cessation
of treatment with six months of either placebo or isoniazid: three in the
isoniazid group and six in the placebo group. This corresponds to an overall
protection of 52%, yet with 95% cent confidence intervals including
zero.
In Nairobi, Kenya, HIV-positive patients were randomly assigned to
receive either daily isoniazid for six months or placebo (irrespective of the
tuberculin skin test result). 888 Outcome measures were incidence of tuberculosis
and death. The follow-up period from enrolment onwards was a
median of 1.8 years. The protection among persons with positive tuberculin
skin test reactions (not further defined) was 40%, yet with confidence
intervals overlapping zero. There was a slight, statistically significant reduction
in risk of death among tuberculin-positive isoniazid recipients compared
to the controls.
Spontaneously healed tuberculosis with fibrotic residuals
Patients with tuberculosis that has healed spontaneously with fibrotic lesions
are frequently found, and remain an important source of reactivation tuberculosis,
particularly in countries where the tuberculosis risk has been rapidly
declining and most cases are the result of endogenous reactivation. Three
such studies are shown here (figure 81).
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Figure 81. Protection from isoniazid preventive therapy against tuberculosis among
patients with fibrotic lesions, hemodialysis, or silicosis. 123,641,891-893
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