Review of Existing Measures

Trevor Hall, PsyD

Introduction

Quality of life has long been recognized as an important aspect of health. In its 30-year history, research on quality of life combined with health related quality of life has generated numerous health related quality of life measurement tools. The origins of health related quality of life research in the 1970s preceded the transformation in the conceptualization of health and function as separate constructs. Consequently, many current measures of health related quality of life are rooted in the presumption that health and functional status are synonymous. For disability and health professionals, it is critically important to disentangle this conceptual confounding. Without distinguishing between health and function in assessment, we cannot use health related quality of life measures to measure one’s perceived health related quality of life.

Research Objective/Research Question or Training Goals

This review had two main purposes. The first was to evaluate the easily accessible/commonly used health related quality of life assessment tools for adequacy to assess health related quality of life for people with disabilities. The second purpose was to gain a consensus regarding desired characteristics of a comprehensive health related quality of life questionnaire that would avoid perceived functional bias.

Methods

Process for Selecting Measures to Review

With the goal of evaluating the status of easily accessible generic (meaning, applicable to all) health related quality of life measures, two methods were used to determine which measures would be reviewed. The first method was a search of the Internet database called the Patient-Reported Outcome and Quality of Life Instruments Database to retrieve a list of, and basic information related to, all known health related quality of life measures. The second method was to utilize the input from a national expert panel to select the final measures for review from the Patient-Reported Outcome and Quality of Life Instruments Database search.

Patient-Reported Outcome and Quality of Life Instruments Database

The Patient-Reported Outcome and Quality of Life Instruments Database is designed and maintained by Mapi Research Trust, as a primary source of information on health related quality of life assessment tools. The Patient-Reported Outcome and Quality of Life Instruments Database is becoming a widely-used resource for health care professionals; thus, the measures contained within the Patient-Reported Outcome and Quality of Life Instruments Database were, for this review, defined as easily accessible/widely used.

Expert Panel

The expert panel process is often used in a range of service fields to identify and improve practice guidelines, evaluate and highlight critical research findings, and suggest priority directions for the future. Researchers at the Research Rehabilitation and Training Center: Health & Wellness for Persons with Long Term Disabilities at Oregon Health & Science University randomly arranged all the questions from measures retrieved from the Patient-Reported Outcome and Quality of Life Instruments Database into an electronic spreadsheet. The spreadsheet was then sent to the members of the national expert panel who then rated the items for content validity. Members of the expert panel were provided with explicit instructions for their review.The completed ratings from the Expert Panel were then sent back to researchers at Oregon Health & Science University and summarized as Content Validity Ratios. The Content Validity Ratio is computed, Content Validity Ratio = (ne – N/2) / (N/2), where ne equals the number of subject matter experts indicating a measurement item is essential, and N equals the total number of subject matter experts in the panel. The Content Validity Ratio equation produces outcome values that range between –1.00 and +1.00, where a Content Validity Ratio of .00 means that 50% of the panel believes the item to be essential. For this review, with an expert panel of 10 members, a .60 Content Validity Ratio was required to meet a .05 significance level of importance. Each measure with at least one essential item (Content Validity Ratio > .60) was retained for the final review of measures.

Process for Reviewing Selected Measures

Each measure was evaluated for its overall performance on the basis of Content Validity Ratio ratings and to obtain information about its use and validation.

Literature Review

The review was limited to articles found using the following keyword searches: assessment, surveillance, quality of life, health status, disability, quality of life + health status + assessment, quality of life + health status + assessment + disability, quality of life + health status + assessment + surveillance, quality of life + health status + assessment + surveillance + disability. Search results were condensed by eliminating non-peer reviewed articles and articles not written in the English language. For measures not mentioned in articles obtained from the literature search, an additional search was conducted. Information for these measures was found in two ways. First, efforts were made to obtain articles cited in the Patient-Reported Outcome and Quality of Life Instruments Database entry for that measure. Second, an additional search was made on MEDLINE and PsycINFO using the name of the measure. To minimize the effects this would have on the literature review process, a maximum of 3 articles was obtained per measure. Research on each measure was reviewed to obtain information about its use and validation.

Results

A total of 85 measures met the original criteria for consideration. This resulted in a total of 648 items for review by the Expert Panel. Based on the review of items by the expert panel, and keeping all measures that had at least 1 essential item using the Content Validity Ratio > .60 criterion, 21 measures were retained. The number of essential items retained was 243. A review of literature was conducted using specific keyword searches. In total, 1,271 abstracts were considered; thereafter, 136 full text articles were retrieved for review. The articles chosen contained information about easily accessible/commonly used generic health-related quality of life measures. A total of 9 measures were not used in any of the articles produced by the literature review. A total of 13 additional articles were gathered to provide basic information about these measures.

Conclusions/Implications

Information gathered from the articles provided an overview of each measure’s use and validation. Information noted from the literature review included evidence for use with special populations, if it had a separate scale for physical function or disease symptoms, if disability groups were used to demonstrate validity, if a low correlation with a measure of physical functioning was used as evidence of validity, and if a high correlation with a measure of physical functioning was used as evidence of validity.In general, when health becomes overly connected with functional status a bias seems to emerge against people with disabilities. The health related quality of life measures reviewed do not appear to be free of biases for people with disabilities. A clear need remains for the development of a generic measurement tool that assesses the health and well-being of adults, is conceptually relevant for disabilities, and separates assessment of health status from functional ability.