Elsevier

The Spine Journal

Volume 18, Issue 7, July 2018, Pages 1292-1297
The Spine Journal

Technical Report
Assessment of health-related quality of life in spine treatment: conversion from SF-36 to VR-12

https://doi.org/10.1016/j.spinee.2018.02.023Get rights and content

Abstract

Background Context

Health-related quality-of-life outcomes have been collected with the Medical Outcomes Study (MOS) Short Form 36 (SF-36) survey. Boston University School of Public Health has developed algorithms for the conversion of SF-36 to Veterans RAND 12-Item Health Survey (VR-12) Physical Component Summary (PCS) and Mental Component Summary (MCS) scores.

Purpose

The purpose of the present study is to investigate the conversion of the SF-36 to VR-12 PCS and MCS scores.

Study Design

Preoperative and postoperative SF-36 were collected from patients who underwent lumbar or cervical surgery from a single surgeon between August 1998 and January 2013.

Methods

Short Form 36 PCS and MCS scores were calculated following their original instructions. The SF-36 answers were then converted to VR-12 PCS and MCS scores following the algorithm provided by the Boston University School of Public Health. The mean score, preoperative to postoperative change, and proportions of patients who reach the minimum detectable change were compared between SF-36 and VR-12.

Results

A total of 1,968 patients (1,559 lumbar and 409 cervical) had completed preoperative and postoperative SF-36. The values of the SF-36 and VR-12 mean scores were extremely similar, with score differences ranging from 0.77 to 1.82. The preoperative to postoperative improvement was highly significant (p<.001) for both SF-36 and VR-12 scores. The mean change scores were similar, with a difference of up to 0.93 for PCS and up to 0.37 for MCS. Minimum detectable change (MDC) values were almost identical for SF-36 and VR-12, with a difference of 0.12 for PCS and up to 0.41 for MCS. The proportions of patients whose change in score reached MDC were also nearly identical for SF-36 and VR-12. About 90% of the patients above SF-36 MDC were also above VR-12 MDC.

Conclusions

The converted VR-12 scores, similar to the SF-36 scores, detect a significant postoperative improvement in PCS and MCS scores. The calculated MDC values and the proportions of patients whose score improvement reach MDC are similar for both SF-36 and VR-12.

Introduction

Patient-reported outcomes (PROs) are essential to the evaluation of spine treatment. The Food and Drug Administration (FDA) requires that the PROs collected in Investigational Device Exemption trials include disease-specific and health-related quality of life (HRQoL) assessments [1]. Although several HRQoL are available, the Medical Outcomes Study (MOS) Short Form 36 (SF-36) has been the most frequently used HRQoL for spine surgery. The FDA specifically mentions the SF-36 in its recommendations for spine Investigational Device Exemption and an article devoted to the SF-36 was published in a spine journal [2]. Despite the creation of the SF-12 (a shorter version of the SF-36) and its validation for spine surgery [3], many spine studies and FDA clinical trials have continued to rely on the SF-36. As a result, SF-36 scores have accumulated for many years on large patient samples.

As will be described later, the short form surveys have a proprietary and a public domain version. The proprietary version uses the trademarked SF-36 and SF-12 names, whereas the public version (with copyright by Trustees of Boston University) is denoted by VR-36 and VR-12. Converting SF-36 to Veterans RAND 12 Item Health Survey (VR-12) scores would enhance the comparability of study results for several reasons. The VR-12 is included in the Medicare Health Outcomes Survey, which has sampled Medicare beneficiaries annually since 1998 [4]. The conversion between VR-12 and PROMIS Global Health is already available [5]. Recently, the Centers for Medicaid & Medicare Services (CMS) has recommended the use of PRO measures that are validated, non-proprietary, and relatively short [6]. The VR-12 was specifically recommended as HRQoL measure in the orthopedic field and will be used by CMS as part of the “Comprehensive Care for Joint Replacement Bundled Payment Model” under “Meaningful Use.”

The conversion of PRO scores to current measures creates several opportunities: the continuity of outcomes in long-term studies, the use of the converted outcomes as historical controls for current studies, and the contribution of HRQoL measures to comparative effectiveness research. Comparative effectiveness research compares the benefits and harms of different diagnostic, treatment, and monitoring methods [7]. Comparative effectiveness research converts HRQoL measures into utility scores, which are included in cost-effectiveness analyses. Two utility indices, the EuroQol instrument (EQ-5D) and the SF-36 derived SF-6D, have been used to assess the comparative effectiveness of the Spine Patient Outcomes Research Trial (SPORT) [8]. SF-6D scores have been predicted from spine-specific measures such as the Oswestry Disability Index and the Neck Disability Index [9], [10]. A utility index, the VR-6D, is also available for the VR-12 and has been found to be similar to the SF-6D [11].

The surveys yield eight scales (vitality, physical functioning, bodily pain, general health perceptions, physical role functioning, emotional role functioning, social role functioning, and mental health) and two summary measures: Physical Component Summary (PCS) and Mental Component Summary (MCS). Researchers at the Boston University School of Public Health [12] have developed and made available algorithms for the conversion of SF-36 to VR-12 scales and summary measures. The purpose of the present study is to investigate the conversion of the SF-36 to VR-12 PCS and MCS scores. Specifically, the present study will compare the average preoperative to postoperative score change, as well as the proportion of patients reaching the minimum clinically important difference (MCID) obtained with the SF-36 and VR-12, respectively. Second, the impact of missing answers will be assessed by comparing the VR-12 scores computed with and without imputation of missing answers (an imputation algorithm is included in the SF-36 to VR-12 conversion algorithms). Finally, SF-36 and VR-12 scores will be directly compared with each other to confirm the necessity of converting SF-36 scores to render them comparable with VR-12 scores.

Section snippets

Sample

The SF-36 scores used in this sample were collected from patients who underwent lumbar or cervical surgery from a single surgeon between August 1998 and January 2013. The sample includes all patients who had completed the SF-36 preoperatively and at 2-year postoperatively or 1-year postoperatively if the 2-year postoperative survey was missing.

PCS and MCS scoring

For the present study, SF-36 PCS and MCS scores were calculated following their original instructions [13], [14]. The SF-36 answers were then converted

Results

A total of 1,968 patients (1,559 lumbar and 409 cervical) had completed preoperative and postoperative SF-36. The postoperative SF-36 consisted of 1-year (n=946) and 2-year (n=1,022) intervals. Results are reported for combined 1-year and 2-year SF-36 as separate analyses yielded similar results. Incomplete answers to the survey resulted in up to 21 unscored SF-36 and up to 129 unscored VR-12, whereas imputing missing values captured all but 2 VR-12 scores. In all comparisons with the SF-36,

Discussion

These results indicate that the converted VR-12 scores are strongly correlated with the original SF-36 scores. When evaluating the treatment effect of spine surgery, the converted VR-12 scores, similar to the SF-36 scores, detect a significant postoperative improvement in PCS and MCS scores. The calculated MDC values and the proportions of patients whose score improvement reach MDC are similar for both SF-36 and VR-12. However, SF-36 scores should not be compared with VR-12 scores without

Conclusions

The conversion of SF-36 to VR-12 scores has been made possible by the development of a public domain algorithm. This score conversion facilitates the adoption of the VR-12 which will contribute to comparative effectiveness research and help participation in CMS regulatory schemes.

Acknowledgment

The authors would like to thank Professor Lewis Kazis for his help and support of this work.

References (34)

  • A.G. Copay et al.

    The minimum clinically important difference in lumbar spine surgery patients. A choice of methods using the Oswestry Disability Index, MOS Short Form 36, and pain scales

    Spine J

    (2008)
  • A.G. Copay et al.

    Understanding the minimum clinically important difference: a review of concepts and methods

    Spine J

    (2007)
  • U.S. Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health

    Guidance document for the preparation of IDEs for spinal systems

    (2000)
  • J.E. Ware

    SF-36 health survey update

    Spine

    (2000)
  • LuoX. et al.

    Reliability, validity, and responsiveness of the short form 12-item survey (SF-12) in patients with back pain

    Spine

    (2003)
  • Centers for Medicare & Medicaid Services

    Health Outcomes Survey (HOS)

  • B.D. Schalet et al.

    Linking Physical and Mental Health Summary Scores from the Veterans RAND 12-Item Health Survey (VR-12) to the PROMIS((R)) Global Health Scale

    J Gen Intern Med

    (2015)
  • American Association of Hip and Knee Surgeons

    Patient-Reported Outcomes Summit for Total Joint Arthroplasty Report

    J Arthroplasty

    (2015)
  • K.G. Abdullah et al.

    Comparative effectiveness research in spine surgery

    Neurosurg Focus

    (2012)
  • A.N. Tosteson et al.

    Comparative effectiveness evidence from the spine patient outcomes research trial: surgical versus nonoperative care for spinal stenosis, degenerative spondylolisthesis, and intervertebral disc herniation

    Spine

    (2011)
  • L.Y. Carreon et al.

    Predicting SF-6D utility scores from the Oswestry disability index and numeric rating scales for back and leg pain

    Spine

    (2009)
  • L.Y. Carreon et al.

    Predicting SF-6D utility scores from the neck disability index and numeric rating scales for neck and arm pain

    Spine

    (2011)
  • A.J. Selim et al.

    A preference-based measure of health: the VR-6D derived from the veterans RAND 12-Item Health Survey

    Qual Life Res

    (2011)
  • Boston University School of Public Health

    VR-36, VR-12, and VR-6D

  • RAND Corporation

    36-Item Short Form Survey (SF-36)

  • J.E. Ware et al.

    SF-36 Physical and mental health summary scales: a user's manual

    (1994)
  • W.H. Rogers et al.

    Imputing the physical and mental summary scores (PCS and MCS) for the MOS SF-36 and the Veterans SF-36 Health Survey in the presence of missing data

    (2004)
  • Cited by (0)

    FDA device/drug status: Not applicable.

    Author disclosures: MFG: Royalties: RTI (F); Stock Ownership: Bonovo (D), International Spine & Orthopedic Institute, LLC (F); Nocimed (A); OuroBoros (C); Viscogliosi Bros Venture Partners LLC (F); Consulting: K2M (E); Medtronic (E); Aesculap (E), outside the submitted work. AGC: Nothing to disclose. KMS: Nothing to disclose. FWS: Nothing to disclose.

    The disclosure key can be found on the Table of Contents and at www.TheSpineJournalOnline.com.

    The Veterans RAND 12-Item Health Survey (VR-12) was developed from the Veterans RAND 36-Item Health Survey (VR-36) which was developed and modified from the original RAND version of the 36-item Health Survey version 1.0 (also known as the “MOS SF-36”).

    SF-36 and SF-12 are registered trademarks of the Medical Outcomes Trust. The VR-36 and the VR-12 are copyrighted by the Trustees of Boston University.

    View full text