Original ArticleA questionnaire found disease-specific WORC index is not more responsive than SPADI and OSS in rotator cuff disease
Introduction
Patient-centered evaluation of pain, disability, and quality of life has been recognized as important in clinical research of interventions for shoulder pain. Many self-administered questionnaires have been developed, but only a few have been thoroughly validated in different clinical settings and by independent researchers [1]. The selection of a proper tool is challenging for most clinicians and researchers. Responsiveness has been defined as the ability to detect change when a real change has occurred [2] and is regarded as a form of construct validity [3]. This is an important characteristic of any measure of treatment effects. Responsiveness of an outcome may depend on several factors such as the patient population studied, type of intervention, timing of data collection, and the construct of change being quantified [4]. Thus, it is necessary to investigate the responsiveness of the outcome measures in different clinical settings [5]. Controversies exist about how to measure responsiveness. Several approaches have been proposed based on study design and the construct of change. The different strategies have been divided into anchor-based and distribution-based methods. The anchor-based method links the instrument to a meaningful external anchor, whereas the distribution-based approaches include methods based on sample variability and measurement precision. As both approaches may have advantages and limitations, there have been authors advocating the use of both anchor- and distribution-based methods [5], [6], [7].
Self-report health assessment questionnaires are classified as generic, region-specific, and disease-specific measures. Specific measures are generally believed to be more responsive than generic measures [8]. Disease-specific questionnaires for patients with shoulder pain have been developed [9]. Region-specific questionnaires have the advantage that the same questionnaire can be used in patients with different diagnoses. A responsive measure will be preferred because the greater the responsiveness of an outcome measure, the fewer the patients required to detect significant between-group treatment effects. The responsiveness of the disease-specific Western Ontario Rotator Cuff index (WORC) has been compared with other region-specific shoulder questionnaires, but the results are diverging and without proper statistical testing of differences between questionnaires [10], [11], [12].
It is often difficult to retrieve what constitutes important changes in self-reported health status questionnaires [3], [7]. Statistical difference is largely dependent on sample size and has little relation to the importance of the observed differences. To guide the interpretation of change scores, estimates of minimum changes in scores that are considered important by patients or clinicians are established [7]. This threshold has been designated the minimal important difference or minimal clinically important change (MCIC). We were not able to find any published studies reporting MCIC values for the WORC index and the Oxford Shoulder Scale (OSS).
The aim of this study is two-fold; first, we want to determine if the responsiveness of the disease-specific WORC index is superior to two commonly used region-specific scales, the OSS and the Shoulder Pain and Disability Index (SPADI) in patients with rotator cuff disease, and second, we want to present estimates of the MCIC of these outcome scores.
Section snippets
Study design and setting
We invited general practitioners in Oslo, serving a population of half a million people, to refer patients with rotator cuff disease to the outpatient clinic of the Physical Medicine and Rehabilitation Department at Oslo University Hospital, Ullevål. All patients were considered for inclusion in a randomized controlled trial comparing systemic and ultrasound-guided corticosteroid injection [13].
We included patients who were at least 18 years old and had all the following: pain on abduction;
Results
Forty-four men and 77 women with a mean age of 51 years [11] participated in the study (Table 1). Two patients did not attend the 2-week follow-up. All patients were encouraged to answer all items in the questionnaires. At follow-up of 2 and 6 weeks, one subject did not fill in WORC and one subject did not fill in OSS and thereby violated the missing rules. At baseline, there were five patients leaving one missing item and two patients leaving two missing items in SPADI, three patients leaving
Discussion
The primary objective of this study was to determine whether responsiveness of the disease-specific WORC index was greater than the region-specific SPADI and OSS shoulder questionnaires. The study sample consisted of 121 patients with a clinical diagnosis of rotator cuff disease who had systemic or local corticosteroid injections. Applying a main complaint scale as an external anchor, all scores showed high SRMs, area under the ROC curves, and RCPs in the improved group. The SRMunchanged and RCP
Conclusion
We conclude that the main finding in the present study suggests that all questionnaires are suitable for measuring change in patients with rotator cuff disease. We did not identify consistent significant differences in responsiveness between the disease-specific WORC index and the region-specific SPADI and the OSS in this patient sample.
Acknowledgments
The University of Oslo funded this study. All authors declare no competing interests. We wish to thank Margrethe Grotle at FORMI, Division for Neuroscience and Musculoskeletal Medicine at Oslo University Hospital, Ullevål, for helpful advices in the planning of this study; the Department of Physical Medicine and Rehabilitation at Oslo University Hospital, Ullevål, for recruitment of patients; and Jan Michael Gran at the Department of Biostatistics at the University of Oslo for help with the
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