The Tourette syndrome diagnostic confidence index - Development and clinical associations

Background: The clinical characteristics of Tourette syndrome (TS) present challenges far the systematic determination of whether individuals are affe cted and severity. Vocal and motor ties wax and wane, decrease over time, a nd may be voluntarily suppressible, and therefore may be absent at intervie w. Current instruments measure symptoms at interview or rate symptom severi ty only. Method: To minimize error in case ascertainment and produce an ins trument measuring lifetime likelihood of having had TS, clinical members of the American Tourette Syndrome Association International Genetic Collabora tion developed the Diagnostic Confidence Index (DCI). The expert group work ed collaboratively with progressive revision in consensus workshops using e xisting diagnostic criteria as guidelines. The DCI produces a score fi om 0 to 100 that is a measure of the likelihood of having or ever having had TS . Results: The DCI was administered to 280 consecutive patients with TS att ending a TS clinic; 264 (94%) completed it, indicating high feasibility and acceptability. Its correlation with other instruments and associations wit h psychopathology provide support for its being a lifetime measure of TS. C onclusions: The DCI is a useful, practicable instrument in the clinic or re search practice allowing an assessment of lifetime likelihood of TS. Furthe r work is needed to test the DCI's psychometric properties, such as its val idity and reliability in populations of interest.