Assessment of pain and disability in patients with chronic low back pain: Reliability and construct validity of the Turkish version of the Quebec Back Pain Disability Scale and Pain Disability Index

Objectives: The objective of this study was to test the reliability and validity of the Turkish version of the Quebec Back Pain Disability Scale (QBPDS) and Pain Disability Index (PDI) as well as the retainment of the psychometric properties of the original versions. The importance of the region-specific functional measures on patients with chronic low back pain was also assessed. Methods: Eighty-three patients with chronic low back pain were enrolled in the study. The QBPDS, the PDI and The Hospital Anxiety and Depression Scale (HADS) were filled by all subjects. Reliability was determined by internal consistency. Internal consistency was measured by calculating Cronbach's alpha and item-total correlation. Validity was examined by correlating the QBPDS and PDI scores to external criteria scores at a single point in time, defined as cross-sectional construct validity. Results: Cronbach's alpha value for QBPDS and PDI was found 0.93 and 0.84 respectively, which were both statistically significant (p < 0.0001). The item-total correlations of QBPDS varied between 0.28 and 0.76, and that of PDI varied between 0.30 and 0.73. The cross-sectional construct validity coefficients of QBPDS were 0.63 for PDI, 0.46 for Visual Analogue Scale (VAS), 0.28 and 0.16 for HADS. Correlation coefficients of PDI were 0.49, and those of VAS and HADS were 0.36 and 0.24 respectively. Conclusion: Our results are in accordance with the previous findings of the English and French versions of the QBPDS and English version of the PDI, indicating that these functional scales are valid and reliable. However, due to the considerable overlap between generic and region-specific functional instruments, the use of both scales is not necessary. We conclude that the QBPDS and PDI both measure predominantly functional status in patients with chronic low back pain.