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
  • 8.5″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
    aphasia. 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)