Comparison of Visual–Motor Skills of Typical Adults With Those of Adults With Parkinson's Disease

RESEARCH HYPOTHESIS: The omnibus research hypothesis of this study is “typical adults will exhibit better visual–motor skills than adults with Parkinson’s disease as measured by scores on the Design Copying (DC) Test.”

RATIONALE: More than 1 million people in the United States have Parkinson’s disease, and each year 60,000 more adults are diagnosed with the disease. Annual direct and indirect costs of the disease in the United States are estimated to be $25 billion. Many adults with Parkinson’s disease have visual–motor problems that prevent them from engaging in occupations and receive occupational therapy services. Occupational therapists (OTs) need evidence-based assessments to evaluate their visual–motor skills.

The DC Test has excellent interrater and test–retest reliability with adults. If the hypothesis that typical adults exhibit better visual–motor skills than adults with Parkinson’s disease is confirmed, the results will demonstrate the test has construct validity. Thus, if the DC Test is shown to be sufficiently sensitive to detect differences in typical adults and those with Parkinson’s disease, the test can be used by occupational therapists to assess some aspects of visual–motor skills of those with Parkinson’s disease.

DESIGN: A nonexperimental, cross-sectional, descriptive design with one independent variable (health status) and three dependent variables was used in this study.

PARTICIPANTS: Using a purposive sampling technique, 19 adults with Parkinson’s disease were each matched to a typical adult on ethnicity, age, gender, and dominance. Inclusion criteria were male or female, fluent in English, independent in activities of daily living and instrumental activities of daily living, either typical or diagnosed with Parkinson’s disease, high school diploma. Exclusion criterion was taking mood-altering drugs.

METHOD: The DC Test was administered and scored according to the manual’s instructions and yielded Accuracy, Approach, and Total scores. Each person was tested individually in a quiet room with only the participant and examiner present.

ANALYSIS: Hotelling’s Trace for paired samples was used to test the omnibus hypothesis and maintain a .05 α level. Results were significant, so post hoc analyses using Bonferroni’s adjustment (paired t tests, each with an α level of .015) were conducted.

RESULTS: Results of Hotelling’s Trace confirmed the hypothesis that typical adults exhibit better visual–motor skills than those with Parkinson’s disease, as measured by the DC Test. Bonferroni adjustments revealed Accuracy and Total scores of typical adults were higher than those of adults with Parkinson’s disease. Using a rigorous alpha level of .015, Approach scores did not differ.

CONCLUSIONS: The DC Test is sufficiently sensitive to detect differences in visual–motor skills of typical adults and adults with Parkinson’s disease. The test detected differences in their accuracy. No differences in how they approach copying tasks were found; that may be a Type II error because the alpha level of .015 was so rigorous.

DISCUSSION: Ayres based the DC Test on research with neurologically impaired adults. This study was undertaken to determine if the test is valid to assess visual–motor skills of adults with Parkinson’s disease. Results using a rigorous α level revealed typical adults perform better on the DC Test than those with Parkinson’s disease. The test, therefore, demonstrates known groups construct validity when used with those with Parkinson’s disease. Thus, OTs have an evidence-based outcome measure to use to assess visual–motor skills of adults with Parkinson’s disease.

IMPACT STATEMENT: OTs need valid measures to assess clients. Results reveal the DC Test is sufficiently sensitive to distinguish between copying of typical adults and those with Parkinson’s disease. Thus, it may be used by OTs to assess some visual–motor skills of those with Parkinson’s disease.