Ontario Society of Occupational Therapists (OSOT) Perceptual Evaluation

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.