Setting: Preventive therapy with isoniazid (INH) is usually recommended for all patients with pulmonary fibrotic lesions compatible with previous tuberculosis (TB).
Objective: To determine the optimal strategy between a 6- to 12-month course of prophylactic INH and therapeutic abstention in different age groups and in patients with severe coexisting diseases that limit life expectancy, such as chronic heart failure (CHF) or chronic obstructive pulmonary disease (COPD).
Design: A Markov decision analysis model that balances the risk of developing active TB against TB-related mortality, the risk of INH-related hepatitis, and INH-related death.
Results: In all groups of patients, prophylactic INH clearly reduced the number of deaths from TB, whereas very few cases died from INH-related toxicity. However, because INH-related deaths occur early, and TB-related deaths occur early or late, the gain in life expectancy was small. Particularly for patients with short survival such as those older than 80 years and those with CHF or COPD, the average gain in life expectancy provided by prophylactic INH did not exceed one week.
Conclusions: Our analysis confirms that prophylactic INH is beneficial to all cohort groups of patients. However, in the case of very old age or severe disease, the gain in life expectancy is minimal. In these cases, the decision to give INH prophylaxis should be tailored on an individual basis with special consideration given to the patient and his environment.