Quality of life assessment after central corpectomy for cervical spondylotic myelopathy: comparative evaluation of the 36-Item Short Form Health Survey and the World Health Organization quality of Life-Bref

Abstract

Object: In this study, the authors assessed the construct validity and the reliability of the World Health Organization Quality of Life-Bref (WHOQOL-Bref) questionnaire in patients with cervical spondylotic myelopathy (CSM) and compared the performance of the WHOQOL-Bref and the 36-Item Short Form Health Survey (SF-36) in assessing quality of life (QOL) in patients with CSM. Methods: In this prospective study, 70 patients with CSM were assessed preoperatively and again 1 year after central corpectomy using the Nurick scale, the SF-36, and the WHOQOL-Bref. Construct validity and reliability of the WHOQOL-Bref, its responsiveness compared with that of the SF-36, and the correlations between the 2 scales were studied. Results: The WHOQOL-Bref was found to be valid (p < 0.001, Cuzick test for trend between the physical domain of the WHOQOL-Bref and Nurick grade) and reliable (Cronbach > 0.7). It had smaller floor and ceiling effects (ranges 1.4-7.1% and 0-7.1%, respectively) than the SF-36 (ranges 2.9-71.4% and 0-14.1%, respectively). There was significant postoperative improvement in patient scores on all the SF-36 scales (p < 0.001) and the physical, psychological, and environment domains of the WHOQOL-Bref (p < 0.001). The SF-36 scales were more responsive to change (relative efficiency range 0.24-1) than the WHOQOL-Bref domains (relative efficiency range 0.002-0.73). Among scales measuring similar concepts, only the physical functioning and bodily pain scales of the SF-36 had a moderate correlation (r = 0.57 and 0.53, respectively; p < 0.001) with the physical domain of WHOQOL-Bref. Many of the scales of these 2 QOL instruments unexpectedly had a fair correlation with one another (r range = 0.2-0.4). Conclusions: The WHOQOL-Bref, like the SF-36, is valid and reliable in assessing outcome in patients with CSM. It measures impairment in CSM in a more uniform manner than the SF-36, but its domains are less responsive to postoperative changes. Because the WHOQOL-Bref measures different constructs and has additive value, it should be used along with the SF-36 for QOL assessment in patients with CSM.