Ontario Society of Occupational Therapists (OSOT) Perceptual Evaluation

Evidence Reviewed as of before: 19-08-2008
Author(s): Lisa Zeltzer, MSc OT
Editor(s): Nicol Korner-Bitensky, PhD O; Elissa Sitcoff, BA BSc

Purpose

The Ontario Society of Occupational Therapists (OSOT) Perceptual Evaluation was designed to assist in the detection of perceptual impairment in adults who have experienced brain damage caused by traumatic brain injury or stroke. The OSOT assesses perceptual dysfunction in areas related to basic living skills. The measure is also used to determine the degree of impairment, to monitor change, and to measure the effects of treatment and/or spontaneous recovery. The OSOT has been standardized for use with individuals aged 40-69 years.

In-Depth Review

Purpose of the measure

The Ontario Society of Occupational Therapists (OSOT) Perceptual Evaluation was designed to assist in the detection of perceptual impairment in adults who have experienced brain damage caused by traumatic brain injury or stroke. The OSOT assesses perceptual dysfunction in areas related to basic living skills. The measure is also used to determine the degree of impairment, to monitor change, and to measure the effects of treatment and/or spontaneous recovery. The OSOT has been standardized for use with individuals aged 40-69 years.

Available versions

The OSOT was created in 1972, by a study group formed in Toronto to discuss perceptual dysfunction in adults with brain damage. However, Boys, Fisher, Holzberg, and Reid (1988) were the first to standardize the OSOT.

Features of the measure

Items:

The original OSOT:

This evaluation consists of 28 subtests that evaluate 6 domains:

(Source: Boys et al., 1988)

Functional Area Test Item Scoring
Sensation Stereognosis
Eight common objects identified by touch
4 = 8/8 correct
3 = 5-7/8 correct
2 = 2-4/8
correct
1 = 0-1/8 correct
Scanning Scanning
Cancellation task (total possible
cancellations = 105)
4 = 0-3 errors
3 = 4-10 errors
2 = 11-25
errors
1 = 26 or more errors
Apraxia Motor Planning
Manipulate 3 wire and grommet devices
4 = 30 seconds (s) or less to complete 3 tasks
3 =
31-60s
2 = 61-90s
1 = unable to complete in less than
91s
Body awareness Parts Recognition
Identify parts of body
4 = 8/8 correct
3 = 5-7/8 correct
2 = 2-4/8
correct
1 = 0-1/8 correct
Spatial relations Environmental
Copy models of 4 pegboard designs
4 = 4/4 correct
3 = 3/4 correct
2 = 2/4
correct
1 = 0-1/4 correct
Visual agnosia Shape Recognition
Match 9 shapes to form board
4 = 9/9 correct
3 = 6-8/9 correct
2 = 2-5/9
correct
1 = 0-1/9 correct

Note: All test items have been recoded into the 4-point format. Only the test item Tactile suppression, which falls under the Sensation domain, is scored in a bivariate form of either 4 = present or 1 = absent.

The revised OSOT:

This evaluation consists of 18 subtests that evaluate 6 domains:

  • Sensation
  • Scanning
  • Apraxia
  • Body awareness
  • Spatial relations
  • Visual agnosia

In order to give the patient precise instructions, the evaluator must state the instructions verbatim prior to administering the OSOT. These instructions can only be repeated once. The evaluator must record all patient responses before offering help.

Scoring:

The OSOT uses a 5-point Likert scale for each of the subtests, ranging from 0 = an inability to do what is asked of the patient, to 4 = normal performance. The scores obtained for each task are added to establish a total score. In the original OSOT, the maximum score that can be obtained is 112. Below is a breakdown of the scores. Each interval corresponds to a degree of severity of the global perceptual impairment:

(Source: Boys et al., 1988)

Score Severity of impairment
110-112 Normal performance
101-109 Borderline case, requires additional testing
91-100 Mild impairment
81-90 Moderate impairment
80 or below Severe impairment

In the revised OSOT, the maximum score that can be obtained is 72. Below is a breakdown of the scores. Each interval corresponds to a degree of severity of the global perceptual impairment:

(Source: Boys et al., 1991)

Score Severity of impairment
70-72 Normal performance
61-69 Borderline case, requires additional testing
51-60 Mild impairment
41-50 Moderate impairment
40 or below Severe impairment

Time:

There is no information published regarding the time it takes to complete the original OSOT, but it is anticipated that it would take longer than the revised OSOT which takes approximately 90 minutes to complete (Tremblay, Savard, Casimiro, & Tremblay, 2004).

Subscales:

The OSOT has 6 subscales or ‘domains’: Sensation; Scanning; Apraxia; Body awareness; Spatial relations; Visual agnosia.

Equipment:

  • Instruction manual
  • Evaluation material
  • Pencil
  • Chronometer
  • 5″x11″ piece of paper
  • Subtests and equipment for each subtest (e.g. a clock, 6 circles out of various sized cardboard, etc).

Training:

The OSOT was created to be used by occupational therapists. An adequate understanding of the instructions and procedures is needed before using the OSOT.

Alternative forms of the OSOT

The revised version of the OSOT (Boys, Fisher, & Holzberg, 1991).

In the revised version of the OSOT, 10 subtests have been eliminated from the 28 found in the original version of the measure.

Client suitability

Can be used with:

Patients with stroke.

Should not be used with:

The OSOT has not been examined for use for patients with An alternative test is the Motor-Free Visual Perception Test, which can sometimes be used to examine the presence of visual perception impairments in patients with expressive aphasia if they are able to understand simple verbal or non-verbal instructions and the various subscale requirements.

In what languages is the measure available?

Validated in French (Desrosiers, Mercier, & Rochette, 1999).

Summary

What does the tool measure? Perceptual impairment in adults (Sensation, Scanning, Apraxia, Body awareness, Spatial relations, Visual agnosia).
What types of clients can the tool be used for? Patients who have experienced brain damage caused by traumatic brain injury or stroke.
Is this a screening or assessment tool? Assessment
Time to administer The revised OSOT takes approximately 90 minutes to complete. There is no information published regarding the time it takes to complete the original OSOT.
Versions Original OSOT (consists of 28 subtests); Revised OSOT (consists of 18 subtests).
Other Languages English and French
Measurement Properties
Reliability
  • Only 1 study has examined the internal consistency of the original OSOT and found alpha coefficients ranging from poor to excellent.
  • Only 1 study has examined the internal consistency of the revised OSOT and reported excellent internal consistency.
  • No studies have examined the test-retest reliability of the OSOT.
  • One study examined the inter-rater reliability of the original OSOT and reported very high agreement (93.1%) across items for all subjects.
Validity

Criterion :

Concurrent:One study reported that the revised OSOT correlated adequately with the Physical Self-Maintenance Scale (PSMS), the Instrumental Activities of Daily Living Scale, and with the Mini-Mental State Evaluation (MMSE).

Construct:

Known groups:

Both the original OSOT and the revised OSOT have been shown to discriminate between patients with acquired brain injury and healthy controls.

Floor/Ceiling Effects No studies have examined the floor or ceiling effects of the OT-APST.
Does the tool detect change in patients? Not Applicable.
Acceptability

The OT-APST is not suitable for individuals:

  • with severe auditory comprehension problems
  • who are unable to use either hand for task completion,
  • whose level of arousal/attentional capacity precludes participation for the necessary time required for task completion
  • with receptive language problems

Alternative methods of test administration are provided for clients with expressive language problems.

Feasibility The OSOT is a lengthy measure to administer and requires an adequate understanding of the test procedures and instructions on the part of the examiner. A number of items are required as equipment for the OSOT, however all items are readily available. The OSOT is simple to score and uses a 5-point Likert scale for each of the subtests. A breakdown of the total score is provided and each interval corresponds to a degree of severity of the global perceptual impairment (e.g. original OSOT: 80 or below represents severe impairment; revised OSOT: 40 or below represents severe impairment).
How to obtain the tool?

The OSOT can be purchased from the publisher:
Nelson, A Thomson Company
1120 Birchmount Road
Toronto, Ontario
M1K 5G4, Canada
E-mail: inquire@nelson.com
Website: http://www.assess.nelson.com/pdf/assessmentcatalogue/cn-19.pdf

Psychometric Properties

Overview

The OSOT has not been well studied. To our knowledge, the creators of the OSOT have personally gathered the majority of psychometric data that are currently published on the scale. The psychometric properties of the original version of the OSOT were based on a study by Boys et al. (1988) of 80 patients with brain damage (experienced a stroke, tumor, normopressure hydrocephalus, or anoxia), and a group of 70 neurologically intact participants. The psychometric properties of the revised version of the OSOT were based on a study by Boys et al. in 1991.

Further investigation on the reliability, validity, and sensitivity of the OSOT is required with larger numbers of subjects. For the purposes of this review, we conducted a literature search to identify all relevant publications on the psychometric properties of the OSOT.

Reliability

Internal consistency:
Original OSOT:
Boys et al. (1988) examined the internal consistency of the original OSOT and reported alpha coefficients ranging from poor (Body Awareness – Parts recognition, alpha = 0.23) to excellent (Sensory Function – Localization, alpha = 0.95).

Revised OSOT:
Boys et al. (1991) examined the internal consistency of the revised OSOT and reported that this version of the OSOT has an excellent internal consistency (Cronbachs alpha = 0.90).

Inter-rater.
Original OSOT:
Boys et al. (1988) examined the inter-rater reliability of the OSOT by having both the attending therapist and one of the investigators score the performance of 46 patients independently, on separate score sheets. Agreement for this study was very high (93.1%) across items for all subjects.

Validity

Criterion:

Concurrent:
Boyd and Dawson (2000) examined the relationship between perceptual impairment and independence in basic and instrumental activities of daily living in a sample of older adults living in an institution or in the community. In this study, the OSOT correlated adequately with the Physical Self-Maintenance Scale (PSMS) (Lawton, & Brody, 1969) (r = 0.44), the Instrumental Activities of Daily Living Scale (r = 0.44), and with the Mini-Mental State Evaluation (MMSE) (Folstein, Folstein, & McHugh, 1975) (r = 0.43). The results of this study suggest that perceptual impairment is related to activities of daily living status.

Construct:

Boys et al. (1988) reported that the moderate correlations observed between scores obtained for each of the 6 domains of the original OSOT demonstrates that each domain measures different concepts, which together give a global perceptual deficit score.

Known groups:
Both the original OSOT and the revised OSOT have been shown to discriminate between patients with acquired brain injury and healthy controls (Boys et al., 1991; Boys et al.,1988). When the performance of patients and control participants were compared in the study by Boys et al. (1988), statistically significant differences were observed for all tests except for Ideational Apraxia.

Sensitivity and specificity:

Boys et al. (1988) reported that the total score of the original version of the OSOT can differentiate between individuals with neurological impairment from neurologically normal control participants. At a total score cutoff of 110, the OSOT can differentiate between individuals with functional impairment and a control group without neurological impairment with a sensitivity of 100% and a specificity of only 40%. At a cutoff of 100, the sensitivity was 63.7% and the specificity was 100%.

Boys et al. (1991) reported that the total score of the revised version of the OSOT can also differentiate between individuals with brain damage from neurologically normal control participants. The sensitivity was 100% with a cutoff score of 70 and over, and of 58% with a cutoff of 60. The specificity was 40% with a cutoff score of 70 and under, and 100% with a cutoff of 60.

References

  • Boyd, A., Dawson, D. R. (2000). The relationship between perceptual impairment and self-care status in a sample of elderly persons. Physical & Occupational Therapy in Geriatrics, 17(4), 1-16.
  • Boys, M., Fisher, P., & Holzberg, C. (1991). The OSOT Perceptual Evaluation Manual: Revised. Scarborough, Ont.: Nelson Canada.
  • Boys, M., Fisher, P., Holzberg, C., & Reid, D. (1988). The OSOT Perceptual Evaluation: A research perspective. American Journal of Occupational Therapy. 42, 92-98.
  • Desrosiers, J.,Mercier, L.,Rochette, A. (1999).Test-retest and inter-rater reliability of the French version of the Ontario Society of Occupational Therapy (OSOT)Perceptual Evaluation. Can J Occup Therapy, 66(3), 134 -139.
  • Folstein, M., Folstein, S., McHugh, P. (1975). Mini-mental State: A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12,189-198.
  • Lawton, M. P., Brody, E. M. (1969). Assessment of older people: self-maintaining and instrumental activities of daily living. Gerontologist, 9, 179-186.
  • Temblay, L. E., Savard, J., Casimiro, L., Tremblay, M. (2004). Répertoire des Outils d’Évaluation en Français pour la Réadaptation (pp406-408). Ottawa, ON: Regroupement des intervenantes et intervenants francophones en santé et en services sociaux de l’Ontario: Université d’Ottawa: CFORP.

See The Measure

The OSOT can be purchased from the publisher:

Publisher address:
Nelson, A Thomson Company
1120 Birchmount Road,
Toronto, Ontario M1K 5G4, Canada
Telephone: 416-752-9448 or 1 800 268-2222
Fax: 416-752-8101 or 1 800 430-4445
E-mail: inquire@nelson.com
Website: http://www.assess.nelson.com/pdf/assessmentcatalogue/cn-19.pdf

Cost: (price is subject to change)
Perceptual evaluation kit (version 2, with English manual): $859
English manual: $75
French manual: $31.80

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