Importance: A reliable observational measure is necessary to measure clients’ behaviors as they participate in activities. The Comprehensive Occupational Therapy Evaluation Scale (COTES) is designed to measure strengths and difficulties in various behaviors that support occupational performance.

Objective: To examine the test–retest reliability of the COTES (overall score and scores on the General Behavior, Social Behavior, and Work Behavior subscales) and calculate the minimal detectable change (MDC) for people with schizophrenia.

Design: Prospective, observational study.

Setting: A psychiatric center.

Participants: COTES data for 118 people with schizophrenia were collected from occupational therapy records. Data from the initial and second COTES measurements were chosen for analysis.

Outcomes and Measures: Test–retest reliability of the overall scale and three subscales was evaluated using the intraclass correlation coefficient (ICC). The MDC was calculated on the basis of the standard error of measurement.

Results: ICCs for the overall scale and three subscales ranged from .91 to .97. The MDC values (MDC%) were 6.5 (10.5%) for the overall scale, 3.4 (13.5%) for the General Behavior subscale, 2.3 (15.2%) for the Social Behavior subscale, and 2.4 (11.0%) for the Work Behavior subscale.

Conclusion and Relevance: The COTES has good test–retest reliability. Clinicians and researchers can use the MDC values provided in this study to explain the implications of change scores for behaviors that affect occupational performance for people with schizophrenia.

What This Article Adds: The COTES has sound reliability and support for its use in determining whether people with schizophrenia make real improvements in behavior that affects occupational performance over time.

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