Association for Academic Surgery
Valuing postoperative recovery: validation of the SF-6D health-state utility

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Abstract

Background

Many surgical innovations are costly but may result in faster patient recovery. Economic analyses of these innovations require utility measures that reflect the construct of “postoperative recovery.” We investigated the validity of Short Form 6D (SF-6D) utility value as a measure of postoperative recovery in patients undergoing elective colorectal resection.

Materials and methods

Patients undergoing elective colorectal resection completed the Short Form 36 and the 6-min walk test at baseline (before surgery) and at 4 and 8 wk postoperatively. SF-6D utilities were derived from the Short Form 36. Longitudinal validity (responsiveness) was assessed using standardized response means (SRM). Construct validity was assessed by comparing the difference in mean SF-6D between patients with and without complications (discriminant) and by correlating the SF-6D with other measures of recovery (convergent).

Results

A total of 191 patients were included (58% male; mean age 63.0 (SD 14.2) y, 81% malignancy, and 54% laparoscopic). SF-6D values dropped significantly from baseline to 4 wk after surgery (SRM −0.54, P < 0.001) and returned to baseline by 8 wk (SRM −0.12, P = 0.111). At 4 wk after surgery, the SF-6D was lower in patients with complications than in those without (mean difference −0.047, 95% CI −0.088, −0.006). At all time points, the SF-6D correlated significantly with the physical and mental component scales of the SF-36 (Pearson r 0.67–0.80, all P < 0.001) and the 6-min walk test (r 0.21–0.29, all P < 0.05).

Conclusions

The SF-6D is a valid measure of postoperative recovery following elective colorectal resection and may be used to measure quality-adjusted life years for cost-effectiveness analyses of surgical technologies and interventions hypothesized to impact recovery.

Introduction

Many surgical innovations in colorectal surgery, such as minimal access techniques and enhanced recovery after surgery pathways, are costly but may result in faster patient recovery. Cost-effectiveness analyses of new technologies are increasingly important in the era of financial constraints in health-care budgets. These studies require appropriate measures of effectiveness. The US Panel on Cost-Effectiveness in Health and Medicine has recommended the measurement of effectiveness in terms of quality-adjusted life years (QALYs), which are calculated by multiplying the time spent in a health state by the quality-of-life weight of that health state, which is measured in terms of utilities [1].

Utility represents the preference of an individual for being in a particular health state, which is defined on a scale from 0–1.0, with 0 representing the worst health/death and 1.0 representing perfect health. This allows for the valuation of health status scaled relative to perfect health and death [2]. In particular, the US Panel recommended the use of preference-based health measures to generate utilities. Examples of these include the Euro-Qol-5D (EQ-5D) [3], Health Utilities Index [4], and the Short Form 6D (SF-6D) [5]. Preference-based health measures that are used to generate utilities differ from other health-related quality-of-life instruments, such as the Short Form 36 (SF-36) [6] and the European Organization for Research and Treatment of Cancer questionnaire [7], in that the latter have no valuation and therefore cannot be used to calculate QALYs. Utilities may also be generic (e.g., the EQ-5D and the SF-6D) or disease-specific (e.g., the King's Health Questionnaire [8] for urinary incontinence). Generic utilities have the advantage of being comparable across studies, but they may be insensitive to disease-specific effects of interventions.

The SF-6D is a generic preference-based health measure that is derived from the SF-36 and is used to generate utilities in order to calculate QALYs for cost-effectiveness analyses. First described by Brazier et al. [5], it has rapidly become one of the most commonly used instruments for measuring utilities, partly because of the widespread use of the SF-36 as a generic quality-of-life instrument. The SF-36 is one of the most commonly reported quality-of-life measures in colorectal surgery [9], and if proved valid, the SF-6D would be a useful adjunct to the SF-36 for use in cost-effectiveness analyses. Although it has been validated for use in endoscopic sinus surgery [10] and carpal tunnel surgery [11], as well as various chronic medical diseases [12], [13], no studies have provided evidence for its validity as a measure of postoperative recovery after major abdominal surgery. Given that faster patient recovery is one of the much-touted benefits of many new surgical techniques, it is important to determine whether a generic utility value is sensitive to the complex “construct” of postoperative recovery. Therefore, the objective of this study is to determine the longitudinal and construct validity of the SF-6D as a measure of postoperative recovery in patients undergoing elective colorectal resection.

Section snippets

Patients

Data previously collected from three clinical trials, including two trials investigating preoperative exercise training [14], [15] and one trial investigating thoracic epidural analgesia versus intravenous lidocaine for perioperative pain management [16], were analyzed. The study population consisted of patients undergoing elective colorectal resection at a single university-affiliated institution between 2005 and 2010. Inclusion criteria for the study were: 18 y of age or older, nonpregnant,

Results

A total of 191 patients were included in the study. Baseline patient demographics and operative characteristics are reported in Table 1. The majority of the patients underwent a segmental colectomy and anastomosis. The overall incidence of complications was 46% (88/191), including 38% (72/191) minor complications and 8% (16/191) major complications. Mean length of stay was 7.7 (19.2) d (median 5 d, interquartile range 4–7). No patients had received adjuvant therapy at 4 wk after surgery,

Discussion

In order to calculate QALYs and perform cost-effectiveness analyses of surgical technologies that may improve recovery after surgery, there is a need for a preference-based health-state utility that is a valid measure of the complex construct of postoperative recovery. In this study, we provide evidence for the responsiveness and discriminant and convergent validity of the SF-6D health-state utility as a measure of recovery after major elective colorectal surgery. Although generic health-state

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    Presented at the Outcomes Plenary Session at the 8th Annual Academic Surgical Congress, New Orleans, Louisiana, February 5, 2013.

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