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April 3, 1987

The Age Threshold for Isoniazid Chemotherapy

JAMA. 1987;257(13):1728-1729. doi:10.1001/jama.1987.03390130046014

To the Editor.—  Although the decision analysis by Rose et al1 applies a useful model to explore how risks and benefits must be weighed in deciding whether the individual with a positive tuberculin reaction should take isoniazid, we believe that the analysis is flawed by two major problems.First, the authors misapplied cross-sectional data to their longitudinal model and thereby greatly overestimated the number of cases of tuberculosis that would be expected over the lifetime of individuals whose only risk factor for the development of tuberculosis is a positive tuberculin reaction. The longitudinal studies cited by Rose et al demonstrate that the longer a tuberculin reactor goes without developing tuberculosis, the lower the likelihood that tuberculosis will develop. Rather than incorporating this fact into their model (or at least performing a sensitivity analysis to demonstrate its implications), the authors merely mention in their discussion that this issue "was not