title: Utility of the hand-drawn spiral as a tool in clinical-epidemiological research on essential tremor: data from four essential tremor cohorts.
abstract: BACKGROUND
  In descriptive epidemiological studies, investigators must screen large numbers of individuals. How one best screens populations for essential tremor (ET); however, remains an open question. The collection of a standardized writing sample (e.g., a hand-drawn spiral) is a method with many practical advantages, yet there are virtually no data on the validity of this particular method.
  
  
  METHODS
  Four hand-drawn spirals (2 right, 2 left) were collected from 831 ET cases across four distinct study settings (population-based study, family study, environmental epidemiological study, brain repository) and, in two of these studies, from 697 controls. Spirals were rated (range 0-3) by a senior movement disorder neurologist. These 1,528 participants also underwent a detailed neurological examination, and total tremor scores (range 0-36) and ET diagnoses were assigned by the neurologist.
  
  
  RESULTS
  The proportion of cases with hand-drawn spiral ratings ≥1.5 in either arm ranged from 78.8-97.0%; only 4.7% of controls had spirals with tremor of that severity. The hand-drawn spiral rating was highly correlated with the total tremor score (r = 0.65-0.73, p < 0.001).
  
  
  CONCLUSIONS
  The hand-drawn spiral is a sensitive and specific method of screening for ET. Furthermore, it serves as a valid measure of overall tremor severity.
authors.affiliation: Department of Neurology, Yale School of Medicine, Yale University, New Haven, Conn., USA.
authors.forename: Elan D
authors.initials: ED
authors.lastname: Louis
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D020329:Essential Tremor / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D009460:Neurologic Examination; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index