FIGURE 1.

This schematic shows the clinical scale development process employed within DID. The process involves development of a conceptual framework for the scale (through input from experts, patients and the literature), development of interview questions to assess symptoms identified during this process, and field testing of items by expert research centers in the target population. Data from this field testing is analyzed synthesized by working group experts before being used to modify the conceptual framework and to guide further interview question development and modification. This process is repeated until all symptoms of interest have been assessed and optimized, a final framework can be assembled, items are finalized for inclusion in the instrument, and formal validation processes undertaken. Figure reproduced with permission: Vaccarino AL, Anderson K, Borowsky B, et al. The Functional Rating Scale Taskforce for Pre-Huntington Disease (FuRST-pHD): an initiative to develop a gold standard instrument to assess early manifestations of Huntington disease prior to formal diagnosis. Presented at International Congress of Parkinson’s Disease and Movement Disorders. Toronto, Canada. June 2011.