title: Videotape tic counts in the assessment of Tourette's syndrome: stability, reliability, and validity.
abstract: OBJECTIVE
  We examined the short- and long-term temporal stability of tic counts to estimate the minimum length of videotape needed for a reliable index of overall tic activity and determined the interrater reliability and validity of tic counts based on prolonged videotape segments (> 10 minutes).
  
  
  METHODS
  Motor and phonic tic counts and clinician ratings were performed on 43 patients with Tourette's syndrome (TS), aged 7 to 50 years. Short-term stability was estimated by determining the mean interval-to-interval correlation of sequential equal-length segments from 30-minute videotape recordings of 20 subjects. Long-term stability was determined by correlating tic counts at 1-week (N = 14) and 2-week intervals (N = 11). In addition, tic counts were correlated with the most widely used clinical ratings of TS.
  
  
  RESULTS
  The short-term stability data indicated that estimates of motor and phonic tic frequencies should be based on videotape counts of at least 5 minutes' duration. Tic counts also were highly reliable and were significantly correlated with clinical ratings with the Yale Global Tic Severity Scale and the Clinical Global Impression Scale for Tourette Syndrome.
  
  
  CONCLUSIONS
  Standardized videotape tic counts can provide highly reliable, stable measures of tic frequencies that are moderately correlated with selected global ratings of tic severity.
authors.affiliation: Child Study Center, Yale University School of Medicine, New Haven, CT 06510.
authors.forename: P B
authors.initials: PB
authors.lastname: Chappell
authors.forename: M T
authors.initials: MT
authors.lastname: McSwiggan-Hardin
authors.forename: L
authors.initials: L
authors.lastname: Scahill
authors.forename: M
authors.initials: M
authors.lastname: Rubenstein
authors.forename: D E
authors.initials: DE
authors.lastname: Walker
authors.forename: D J
authors.initials: DJ
authors.lastname: Cohen
authors.forename: J F
authors.initials: JF
authors.lastname: Leckman
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D002648:Child; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009270:Naloxone / Q000627:therapeutic use; D011569:Psychiatric Status Rating Scales; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D013981:Tic Disorders; D005879:Tourette Syndrome / Q000175:diagnosis* / Q000188:drug therapy; D014743:Videotape Recording
chemical_list: D009270:Naloxone