Letters Section Editor: Robert M. Golub, MD, Senior Editor.
In Reply: In response to Dr Damián, we had considered including details of the treatment analysis. However, it would have been necessary to analyze both the interactions with treatment components considered separately (antioxidants vs placebo, zinc vs placebo) as well as in combination (antioxidants with zinc vs placebo). Furthermore, it is important to consider both quantitative interactions (when the direction of the effect is the same in 2 treatment groups, but the magnitude is different) and qualitative interactions (when the direction of the effect is different in different treatment groups). However, these analyses are complex, and we believed that to do justice to the treatment data and not make this article too cumbersome to interpret, the genotype-treatment data would be best presented in a separate publication.
Seddon JM, Francis PJ, Klein ML, Rosner B. Genetic Associations With Age-Related Macular Degeneration—Reply. JAMA. 2007;298(14):1637. doi:10.1001/jama.298.14.1637-b