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 α > 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.