The purpose of this study is to define what treatment outcome satisfaction (TOS) means for the patient with low back pain (LBP) and to develop a theoretically-based, valid and reliable measure to assess this construct in a physical therapy setting. Two preliminary studies were conducted to provide support for the main study: (1) An explorative study that examined the concept of TOS at the end of a physical therapy (PT) intervention, and (2) A cross-sectional study that evaluated the content, face validity, and internal consistency of a TOS questionnaire (TOSQ).

Methods. A longitudinal study established construct validity by evaluating the content, convergent, and discriminate validity of a TOSQ. Data were collected using three methods: written, phone, and proxy.

Results. An exploratory and confirmatory factor analysis detected one factor that accounted for 58% to 78% of the total variance in the multidimensional questionnaire depending on the method of data collection (written, phone, or proxy). All of the items highly and significantly correlated with each other and with the global measures of satisfaction, demonstrating good internal consistency and concurrent validity. Cronbach's alpha (α) values were calculated to find the most homogenous set of items. The highest α and average inter-item correlation in all of the cases was found when eight items were included. Criterion validity was supported by the strong correlations between each of the specific items and the two global items, and the significant association between the total score of the TOSQ and these global questions. Convergent validity was established as TOS was associated with the theoretical models of performance, expectation/disconfirmation, and embodiment. Discriminate validity was suggested by the low associations with process and structure of care satisfaction. Results remained similar for all methods of data collection.

Conclusions. TOS was found to be a complex attitude reflected in the patient's beliefs, emotional responses, and behavioral reactions resulting from the physical therapy (PT) intervention. Construct validity of the TOSQ was proven through content, face, criterion, convergent, and discriminant validity. This research project was successful in developing a valid TOSQ for patients with LBP in a PT setting.