Introducing a new health-related quality of life outcome tool for metastatic disease of the spine: content validation using the International Classification of Functioning, Disability, and Health; on behalf of the Spine Oncology Study Group

Abstract

Study design: A systematic review of Health Related-Quality of Life Outcomes (HRQOL) in metastatic disease of the spine and content validation of a new Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ).

Objective: To identify HRQOL questionnaires previously reported for spinal metastases and to validate the content of the new SOSGOQ based on the International Classification of Function and Disability (ICF).

Summary of background data: Literature on metastatic tumors of the spine and clinical outcomes is limited and generally of poor quality. The SOSG has developed a "quality of life" outcome tool specific for patients with metastatic of the spine. The ICF is a universal framework allowing content exploration, comparison, and validation of all questionnaires relating to HRQOL.

Methods: A systematic review identified 141 studies. Reported outcome tools were enumerated. The most commonly used (ESAS, Karnofsky Scale, and Oswestry Disability Index) and the SOSGOQ were linked to the ICF. Descriptive statistics examined the frequency and specificity of the ICF linkage. Linkage reliability was evaluated by interinvestigator percentage agreement.

Results: The SOSGOQ contains 56 concepts, with all 4 domains of the ICF represented. Four concepts could not be linked. There was 100% interobserver agreement (IOA) for total number of concepts and for those "not covered." Hundred percent of concepts had "First and Second" level linkage. Hundred percent IOA exists at both "Component" and "First Level" linkage. There was 96.1% IOA at "Second Level". Thirty-three concepts linked to Third Level with 96.9% IOA. Ten concepts linked at the Fourth Level with 100% IOA.

Conclusion: The SOSGOQ includes all domains relevant for measurement of function and disability and its content validity is confirmed by linkage with the ICF. This new questionnaire has superior content capacity to measure disease burden of patients with metastatic disease of the spine than any instruments previously identified in the literature.