The Responsiveness of Three Persian Outcome Measures Following Physiotherapy Intervention in Patients with Chronic Non-Specific Neck Pain

Objectives: A prospective cohort study to evaluate and compare the responsiveness of the Persian version of the neck disability index (NDI), neck pain disability scale (NPDS), neck outcome score (NOOS), and to determine the minimal clinically important difference (MCID) and minimal detectable change (MDC). To date, no studies have made a direct comparison between the responsiveness of the Persian version of NPDS, NDI, and NOOS questionnaires. Methods: At the end of the study, 55 patients with chronic non-specific neck pain completed the NPDS, NDI, and NOOS questionnaires at the beginning and end of three weeks of physiotherapy treatment. Additionally, patients completed the global rating of change scale to differentiate between improved and unimproved patients. Comparison of responsiveness was performed using anchor-based methods (receiver operating characteristic (ROC) curve and correlation analysis). MCID and MDC were assessed to investigate relevant changes for each questionnaire. Results: ROC curves analysis showed areas under the curves of 0.70, 0.64, and 0.43 to 0.63 for the NPDS, NDI, and NOOS subscales, respectively. The correlation coefficients between the global rating of the change scale and the change scores of the NPDS and NDI were 0.38 (P 0.01) and 0.30 (P 0.05), respectively. There were no significant correlations between NOOS subscales and global rating of change score (r=0.001- 0.21, P 0.05). The MCID for the NPDS, NDI, and NOOS subscales were 28.09 (score 0-100), 7.5 (score 0-50), and 13.75 to 28.64 (score 0-100), respectively. The MDCs were found to be in the following order: 47.1 points for NPDS, 36.1 for NDI, and 23.5 to 39.7 for NOOS subscales. Conclusion: The Persian NPDS seems more responsive than the NDI and NOOS questionnaires. The level of clinically meaningful change in NDI, NPDS, and NOOS questionnaires is in the range of measurement error.