The two different methods of determining age of onset (i.e., a single self-report item or responses to a semi-structured interview) showed comparable validity. A recent systematic review of factors affecting the implementation of information technologies in clinical settings (Gagnon et al. 2010) showed ease of use to be an important factor promoting the adoption of new technology. Thus, given the greater simplicity of the single-item measure, we would anticipate that it would be the better approach to use clinically (and, possibly, in treatment guidelines). However, other considerations, such as the psychometric properties of the measure should be included in this determination. Thus, research on the temporal stability of the age-of-onset measure is needed.
