The Canine Orthopedic Index. Step 2: Psychometric testing.

OBJECTIVE: To perform psychometric testing an owner self-administered questionnaire, the Canine Orthopedic Index (COI), designed to assess outcome in dogs with orthopedic disease. STUDY
DESIGN: Original study. SAMPLE POPULATION: Owners (n = 20) of dogs with osteoarthritis (OA) for item (question) pretesting, and 80 owners of dogs with OA for reliability and validity testing.
METHODS: Standard methodology for the stepwise development and testing of instruments designed to assess subjective states was followed. Items generated in previous studies were pretested for readability, ambiguity, and inter-item correlations; poorly performing items were removed; and the reduced set of items subjected to factor analysis, reliability, and validity testing.
RESULTS: Four factors were identified and named on the basis of the items contained in them: "Stiffness," "Gait," "Function," and "Quality of Life." Cronbach's α ranged from 0.76 to 0.86, suggesting the items in each factor could be assessed as a group to compute factor scores (i.e., stiffness, gait, function, and quality of life scores). The test-retest analysis revealed κ values from 0.68 to 0.80. Overall, the scores amongst the 4 factors correlated moderately well (r = 0.52-0.58), with a mild correlation (r = 0.35) between gait and function scores.
CONCLUSIONS: The COI is a psychometrically sound owner completed instrument that can assess 4 domains in dogs with OA: Stiffness, Gait, Function, and Quality of Life. © Copyright 2014 by The American College of Veterinary Surgeons.