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Volume 12, Number 5—May 2006
THEME ISSUE
Tuberculosis Special Section

Research

Isoniazid Preventive Therapy and Risk for Resistant Tuberculosis

Maria Elvira Balcells*1, Sara L. Thomas*, Peter Godfrey-Faussett*, and Alison D. Grant*Comments to Author 
Author affiliations: *London School of Hygiene and Tropical Medicine, London, United Kingdom

Main Article

Table 1

Assumptions underlying the analysis

Assumption Comment
When a sample of culture positive isolates underwent resistance testing, this was a random sample of all cases. Additional variation incurred by sampling tuberculosis (TB) cases for resistance was incorporated into 95% confidence interval estimates and thus the weighting of studies in meta-analyses.
Differential ascertainment of resistance is unlikely because most of the included studies were double-blinded and (for studies in which information was available) similar proportions of culture-positive TB cases from each group were tested.
Latent infection with isoniazid-resistant TB was equally distributed between comparison groups. 12 of 13 studies were comparisons of randomized groups; any latent infection with a resistant organism would likely be equally distributed between comparison groups. Any imbalance due to random error would be bidirectional and so would result in summary estimate of relative risk tending towards 1 (i.e., being underestimated).
Risk for isoniazid-resistant TB resulting from recent infection was equally distributed between comparison groups. Similarly, any new infection with an isoniazid-resistant organism would likely be equally distributed between randomized groups. Any imbalance would similarly result in summary estimate of relative risk being underestimated.

Main Article

1Current affiliation: Department of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile

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