Ontario Society of Occupational Therapists (OSOT) Perceptual Evaluation

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).