Does interval between screening and baseline matter in HD cognitive clinical trials?

J Huntingtons Dis. 2014;3(2):139-44. doi: 10.3233/JHD-140100.


Background: "Practice effects" (PE), or performance improvements due to prior exposure to testing, are known to confound cognitive test results, particularly when short intervals occur between two test sessions.

Objective: We examined two subsamples with short or long re-test intervals from a recent clinical trial.

Methods: Thirty-four non-depressed adults with mild Huntington Disease (HD) participated. Three cognitive tests were administered at screening and again at baseline, before active treatment randomization. Half the sample had a 24-hour retest interval while the other half was >6-days.

Results: The two groups differed on demographic/clinical factors (age, Total Motor Score and Total Functional Capacity). After controlling for age and motor score, PE differences were found on three of the five UHDRS cognitive tests: the longer interval group showed larger PE on Symbol-Digit Modalities and Stroop color, while the rapid interval group had larger PE on Stroop interference. Controlling for screening cognitive performance yielded similar results.

Conclusions: Length of interval between screening and baseline visits and level of disease severity may influence stability of UHDRS cognitive test results in clinical trials in HD.

Trial registration: NCT00271596.

Keywords: Huntington disease; cognitive disorders/dementia; neuropsychological assessment; practice effects.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cognition / drug effects
  • Cognition Disorders / diagnosis*
  • Cognition Disorders / etiology*
  • Cognition Disorders / psychology
  • Dementia / diagnosis*
  • Dementia / etiology*
  • Dementia / psychology
  • Disease Progression
  • Female
  • Humans
  • Huntington Disease / complications*
  • Huntington Disease / drug therapy*
  • Huntington Disease / psychology
  • Male
  • Middle Aged
  • Neuropsychological Tests
  • Severity of Illness Index
  • Time Factors

Associated data