Ontario Society of Occupational Therapists Perceptual Evaluation (OSOT)

CHAPTER 102: ONTARIO SOCIETY OF OCCUPATIONAL THERAPISTS PERCEPTUAL EVALUATION (OSOT)

Description

The Ontario Society of Occupational Therapists Perceptual Evaluation (OSOT) (1972) is a standardized assessment developed to test the perceptual capabilities of impaired individuals and its results can provide a measure of an individual’s perceptual dysfunction in areas related to basic living skills, determine his or her degree of impairment, monitor change, and measure the effects of treatment and/or spontaneous recovery (Boys, Fisher, & Holzberg, 1991; Toglia & Kirk, 2000). The OSOT consists of 18 tasks organized into 6 functional areas that measure (1) scanning neglect, (2) apraxia, (3) body awareness, (4) visual agnosia, (5) spatial relations, (6) and stereognosis. Each subtest is in the form of behavioral performance tasks that test an individual’s motor skills, eye-hand coordination, and visual recognition (Boys, Fisher, Holzberg, & Reid, 1988). The test involves several activities such as recognizing an object using only touch (stereognosis), scanning items for elimination (visual scanning), solving a puzzle of a human figure (body awareness), and stacking blocks (spatial relations). The assessment uses variable 5-point interval scoring systems (0 to 4) that are unique for each item. For example, the ability to manipulate wire grommet devices would be scored as (4) 30 seconds or less to complete 3 tasks, (3) 31 to 60 seconds, (2) 61 to 90 seconds, or (1) unable to complete in less than 91 seconds. The OSOT can be completed in less than 30 minutes with lower scores suggesting more severe impairment.

Psychometrics

When Desrosiers, Mercier, and Rochette (1999) translated the OSOT into French, using a sample of 32 subjects post-traumatic brain injury (TBI), they found overall test-retest reliability to be r = 0.93 and intra-rater reliability to be r = 0.98. A study of 76 subjects who were either residents of long-term care facilities or older adults living in the community referred to for occupational therapy assessment found inter-rater reliability to be r = 0.84 while perceptual status, as measured by the OSOT was highly correlated with the Physical Self-Maintenance Scale at 0.44, the Instrumental Activities of Daily Living (IADL) scale at 0.44, and the Mini-Mental Status Examination (MMSE) at 0.43 (Boyd & Dawson, 2000). Further results found that mean scores for the experimental group were 60.80 (range: 32 to 71) and for controls they were 69.37 (range: 101 to 112), suggesting an ability to detect impairment (Boyd & Dawson, 2000). Early research into the OSOT using a sample of 46 subjects determined inter-rater reliability to be r = 0.93 using 2 raters with item total correlations ranging from 0.63 to 0.85 with the exceptions of parts recognition at 0.23, ideomotor at 0.24, ideational apraxia at 0.29, right stereognosis at 0.33, and laterality at 0.46 (Boys et al., 1988). The same study found that mean total scores for the experimental group were 88.1 whereas control group scores were 108.38, also suggesting that the test is able to detect impairment. Additionally, at a score of 110 the sensitivity of the instrument was 100% and specificity was 40% (Boys et al., 1988). At a cutoff score of 100, the sensitivity was 63.7% and the specificity was 100% indicating that a score of 100 optimizes specificity, whereas 110 may optimize its sensitivity (Boys et al., 1988).

Advantages

The OSOT perceptual battery has been able to demonstrate high inter- and intra-rater reliabilities in light of the fact that there are 18 varying items. It has also shown to correlate well with other measures such as the IADL scale and the MMSE, which is the gold standard of cognitive testing. It is also an occupational therapy specific outcome measure.

Disadvantages

There is a limited amount of research in support of its use in clinical practice and that which is available is dated. Also, population studies have so far been limited to only TBI patients. The assessment can be time consuming requiring both an amount of time to set up and administer. Alas, it is costly at ≥ $900.

Administration

The OSOT is a standardized assessment that when purchased includes a detailed manual for its administration and scoring. The OSOT consists of 18 activities and uses several 5-point-interval scoring systems (0 to 4) unique for each item. A total score of 91 to 100 suggests mild impairment, 81 to 90 suggests moderate impairment, and a score of 80 or below indicates severe impairment.

Permissions

The OSOT Perceptual Evaluation Kit can be purchased from Nelson Education or other therapy equipment suppliers for $925. Permission to use in research and publication can be obtained by contacting the copyright holders of the measure or where purchased. More information can be found in the following journal article:

Boys, M., Fisher, P., Holzberg, C., & Reid, D. W. (1988). The OSOT Perceptual Evaluation: A research perspective. American Journal of Occupational Therapy, 42(2), 92-98.

Summary

POPULATION	Validated in TBI
TYPE OF MEASURE	Activity-based rating scale of performance
WHAT IT ASSESSES	Perceptual dysfunction in daily skills
TIME	< 30 minutes
COST	$925