Validity, Reliability, and Responsiveness of the Spanish Version of the OPTIMAL Instrument.

Background: The Outpatient Physical Therapy Improvement in Movement Assessment Log (OPTIMAL) is a self-report instrument developed to measure the ability to perform mobility actions.

Objective: To validate a Spanish version of the OPTIMAL instrument.

Design: Cross-cultural adaptation and validation study.

Setting: Primary and specialized outpatient care settings.

Participants: Three hundred seven patients beginning physical therapy treatment and 30 subjects from the general population.

Methods: A 2-part study was designed based on guidelines for cultural adaptation of patient-reported outcome measures.

Outcomes: Reliability was estimated by internal consistency (Cronbach α), SE of measurement, and test-retest reliability (intraclass correlation coefficient) at 2 weeks. Confirmatory factor analysis was performed to examine structural validity. The association with the Physical Functioning Subscale was assessed with Spearman correlation coefficients. OPTIMAL scores across different groups were compared with Mann-Whitney U and Kruskal-Wallis tests. Effect size, standardized response mean, and minimal detectable change were determined for responsiveness.

Results: The Spanish version of the OPTIMAL instrument showed a similar structure to the original English questionnaire. Cronbach α was 0.95 for the difficulty and confidence scales. Intraclass correlation coefficient was 0.91 (95% CI 0.87-0.94) for the difficulty scale and 0.90 (95% CI 0.85-0.93) for the confidence scale. The SE of measurement was 5.11 for the difficulty scale and 6.54 for the confidence scale. The association with the Physical Functioning Subscale was strong and significant (P < .001). The 2 scales showed significantly different scores for each of the established patient groups. The effect size was 0.61 (95% CI 0.48-0.74) for the difficulty scale and 0.53 (95% CI 0.38-0.69) for the confidence scale. The standardized response mean was 0.97 (95% CI 0.78-1.13) for the difficulty scale and 0.76 (95% CI 0.48-1.01) for the confidence scale. The minimal detectable change, of a possible score of 100, was 14.2 for the difficulty scale and 18.1 for the confidence scale.

Conclusion: The Spanish version of the OPTIMAL has appropriate reliability, validity, and responsiveness and it is an adequate self-report instrument for the assessment of mobility actions.

Level Of Evidence: III.