Occupational therapy assessment and treatment of perceptual impairments are integral to the rehabilitation of clients following stroke and other forms of acquired brain injury. The purpose of this study was to establish the psychometric properties of a new screening tool for visual perceptual impairment in adults following stroke developed by the researcher - the Occupational Therapy Adult Perceptual Screening Test (OT-APST). The OT-APST takes approximately 20 minutes to administer and contains items to screen for visual perceptual impairments across each of the constructs of agnosias, visuospatial skills (including awareness of body scheme and unilateral neglect), constructional skills, apraxia and acalculia. The OT-APST is a screening tool to detect changes in visual perceptual skills and to determine the need for more in-depth assessment of impairment areas following stroke and other forms of acquired brain injury. The specific aims of the study included determining the clinical utility, content validity and face validity of the OT-APST, establishing the reliability of the OT-APST, establishing the construct, criterion and ecological validity of the OT-APST, and establishing adult normative data for this new screening tool.
To achieve these aims, the study was conducted in four phases. Phase 1 involved a preliminary survey of occupational therapists and expert panel reviews, with both stages followed by revisions to the OT-APST to improve its clinical utility, content validity and face validity. In Phase 2 of the study, the examination of three aspects of test reliability including inter-rater reliability, intra-rater reliability and test-retest reliability of the OT-APST was undertaken through video recordings of people completing the OT-APST at different time intervals following stroke. Fifteen people following stroke were included in the inter-rater and intra-rater reliability study and 10 people in the test-retest reliability study. Ten occupational therapists were involved in rating these performances as part of the reliability studies. Phase 3 of the study involved exploration of the construct validity of the OT-APST through scale validation, convergent validity, and ecological validity methods, and examination of the concurrent criterion validity of the OT-APST for a sample of people with stroke. Two participant groups were recruited for the third phase, including a sample of 208 people following stroke and 356 healthy adults. The fourth phase of the study included examination of the perceptual skill performance characteristics of the healthy participant group in order to establish the normative data for the OT-APST.
The Phase 1 survey of 56 occupational therapy practitioners on the clinical utility and content of the original version of the perceptual screening test provided support for its clinical usefulness. The expert panels, comprising 13 occupational therapists, further explored issues related to perceptual screening and assessment raised in the survey, and endorsed the clinical utility, content validity and face validity of the revised OT-APST.
The findings of Phase 2 revealed that the OT-APST has a high level of inter-rater, intra-rater and test-retest reliability for all items, and that the levels of reliability are comparable to other visual perceptual assessment tools.
The results of Phase 3 supported the construct validity of the OT-APST through exploration of the scale design using factor analysis and internal consistency measurement, convergent validity correlations and 'separation of known groups method' with the two participant groups. Concurrent criterion validity of the OT-APST was demonstrated through correlation of the performance of people following stroke on a 'gold standard' reference tool and analysis of test sensitivity and test specificity. Finally, ecological validity was examined through correlation of the performance of the participants with stroke on the OT-APST with a measure of functional independence.
Phase 4 analyses yielded age-stratified normative data for OT-APST interpretation, including the determination of cut-off scores for each subtest. Normative data with cut-offs will enable occupational therapists to make norm-referenced interpretations of OT-APST performance for individual clients for use in treatment planning and education. The incidence of perceptual impairments in the two participant groups was compared, and factors influencing OT-APST performance for the healthy participants examined.
In summary, the OT-APST is a brief but comprehensive, reliable and validated screening tool for visual perception. It systematically screens the main perceptual constructs including a wide range of perceptual impairments that may occur after stroke. This study demonstrates the psychometric properties of reliability (inter-rater, intra-rater and test-retest reliability) and validity (face, content, construct, criterion and ecological validity) and provides a large and age-stratified normative data set. The study participants reflect the population for whom the test is designed. Factors that may have impacted on the results were identified, and recommendations for further research in this area are suggested.