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Summary/Overview of Instrument: Spot the Change is a visual working memory task in which subjects are presented briefly with a computer screen showing 5 colored squares. The screen then displays the same squares in the same position, but with 1 square circled. Subjects were asked to indicate, within a specified time, whether the color of the circled square had changed.

Construct measured: Visual working memory.

Generic vs. disease specific: Generic.

Intended use of instrument/purpose of tool (cross-sectional, longitudinal, diagnostic, etc): Assessment of cognitive function in HD cross-sectional and longitudinal studies.

Means of administration (paper and pencil, computerized): Computerized.

Location of administration (clinic, home, telephone, etc): Clinic.

Intended respondent (patient, caregiver, etc.): Patient.

# of items: N/A.

# of subscales and names of sub-scales: N/A.

Strengths: This task is nonverbal and is feasible for use across languages. The response does not rely on motor speed or fine motor control as task performance requires only an untimed button press.

Weaknesses: Ideally, multiple set sizes would be used but this would increase test time. Track-HD found that set size 5 was neither at ceiling nor at floor for controls, pre- manifest, and early HD. However, set size 3 approached ceiling in controls and pre- manifest subjects far from onset whereas set size 7 began to approach floor in Early HD subjects.

Special Requirements for administration: Computer and mouse.

Administration Time: 8 minutes.

Translations available (e.g. Spanish, French, Other languages): French, Dutch, and English.

Reliability:

Test-retest or intra-interview (within rater) reliability (as applicable): 24-month test- retest correlations ranged from .34 to .60 in controls, late pre-manifest HD, and early (stage 1) HD in the TRACK-HD study.

Inter-interview (between-rater) reliability (as applicable): N/A.

Internal consistency: N/A.

Statistical methods used to assess reliability: test-retest correlation.

Reliability data from the CAB study will be available by end of 2012 for 100 control, 100 pre-manifest, and 50 early HD subjects.

 

Validity:

Content validity: N/A.

Construct validity: N/A.

 

Sensitivity to Change/Ability to Detect Change (over time or in response to an intervention): In TRACK-HD, cross-sectional differences from controls were detected in pre-manifest HD and early HD (Tabrizi et al, 2009); longitudinal rate of change (annualized over 24 months) in early HD but not pre-manifest HD differed from rate of change in controls (Tabrizi et al., 2011; Stout et al., in submission).

 

Known Relationships to Other Variables (e.g. gender, education, age, etc): In TRACK- HD, performance was related to age and education but not gender; change in performance was not related to age, gender or education.

 

Diagnostic Sensitivity and Specificity, if applicable (in general population, HD population- pre-manifest/ manifest, other disease groups):