Lidia Engel

Short form health surveys and related variants in spinal cord injury research : a systematic review

Abstract Context ‘Short Form’ health surveys – such as the SF-36 and SF-12 – are widely used in medical research. Spinal cord injury (SCI) is no exception, despite oft-cited concerns regarding measurement properties for populations with physical impairment. Objective To provide a comprehensive overview of the use of Short Form health surveys and their variants within the SCI literature. Methods Papers published between database inception and September 2012 were identified from 11 electronic databases; a supplementary reference list search was also conducted. Data extraction focused on details regarding the range of different Short Form surveys and variants used in SCI research, the respective frequency of use, the nature of reporting (complete versus partial reporting) and the method of survey administration. Results One hundred seventy-four papers were identified. Thirty-six-item Short Form health surveys were frequently administered as complete instruments (n = 82); in 69 of these 82 studies (84%), it was not clearly stated which 36-item version had been used (e.g. SF-36v1, SF-36v2, RAND-36). Data for individual items and domains were often reported (29% of identified studies), indicating significant partial use of standardized measures. Modified variants of standardized health surveys were administered in 12 studies. Conclusion Although standardized Short Form health surveys are common within SCI research, attempts to add, delete, or modify items have resulted in a number of variants, often with minimal supportive psychometric evidence. Using established, generic outcome measures is appealing for a number of reasons. However, validity is paramount and requires further explicit consideration within the SCI research community.

EXCLUSION CRITERIA IN NATIONAL HEALTH STATE VALUATION STUDIES: A SYSTEMATIC REVIEW

Background. Health state valuation data are often excluded from studies that aim to provide a nationally representative set of values for preference-based health-related quality of life (HRQoL) instruments. The purpose was to provide a systematic examination of exclusion criteria used in the derivation of societal scoring algorithms for preference-based HRQoL instruments. Methods. Data sources included MEDLINE, official instrument websites, and publication reference lists. Analyses that used data from national valuation studies and reported a scoring algorithm for a generic preference-based HRQoL instrument were included. Data extraction included exclusion criteria and associated justifications, exclusion rates, the characteristics of excluded respondents, and analyses that explored consequential implications of exclusion criteria on the respective national tariff. Results. Seventy-six analyses (from 70 papers) met the inclusion criteria. In addition to being excluded for logical inconsistencies, respondents were often excluded if they valued fewer than 3 health states or if they gave the same value to all health states. Numerous other exclusion criteria were identified, with varying degrees of justification, often based on an assumption that respondents did not understand the task or as a consequence of the chosen statistical modeling techniques. Rates of exclusion ranged from 0% to 65%, with excluded respondents more likely to be older, less educated, and less healthy. Limitations included that the database search was confined to MEDLINE; study selection focused on national valuation studies that used standard gamble, time tradeoff, and/or visual analog scale techniques; and only English-language studies were included. Conclusion. Exclusion criteria used in national valuation studies vary considerably. Further consideration is necessary in this important and influential area of research, from the design stage to the reporting of results.

Perceptions of individuals living with spinal cord injury toward preference-based quality of life instruments: a qualitative exploration

BackgroundGeneric preference-based health-related quality of life instruments are widely used to measure health benefit within economic evaluation. The availability of multiple instruments raises questions about their relative merits and recent studies have highlighted the paucity of evidence regarding measurement properties in the context of spinal cord injury (SCI). This qualitative study explores the views of individuals living with SCI towards six established instruments with the objective of identifying ‘preferred’ outcome measures (from the perspective of the study participants).MethodsIndividuals living with SCI were invited to participate in one of three focus groups. Eligible participants were identified from Vancouver General Hospital’s Spine Program database; purposive sampling was used to ensure representation of different demographics and injury characteristics. Perceptions and opinions were solicited on the following questionnaires: 15D, Assessment of Quality of Life 8-dimension (AQoL-8D), EQ-5D-5L, Health Utilities Index (HUI), Quality of Well-Being Scale Self-Administered (QWB-SA), and the SF-36v2. Framework analysis was used to analyse the qualitative information gathered during discussion. Strengths and limitations of each questionnaire were thematically identified and managed using NVivo 9 software.ResultsMajor emergent themes were (i) general perceptions, (ii) comprehensiveness, (iii) content, (iv) wording and (v) features. Two sub-themes pertinent to content were also identified; ‘questions’ and ‘options’. All focus group participants (n = 15) perceived the AQoL-8D to be the most relevant instrument to administer within the SCI population. This measure was considered to be comprehensive, with relevant content (i.e. wheelchair inclusive) and applicable items. Participants had mixed perceptions about the other questionnaires, albeit to varying degrees.ConclusionsDespite a strong theoretical underpinning, the AQoL-8D (and other AQoL instruments) is infrequently used outside its country of origin (Australia). Empirical comparative analyses of the favoured instruments identified in this qualitative study are necessary within the context of spinal cord injury.

“When I saw walking I just kind of took it as wheeling”: interpretations of mobility-related items in generic, preference-based health state instruments in the context of spinal cord injury

BackgroundIn health economic analyses, health states are typically valued using instruments with few items per dimension. Due to the generic (and often reductionist) nature of such instruments, certain groups of respondents may experience challenges in describing their health state. This study is concerned with generic, preference-based health state instruments that provide information for decisions about the allocation of resources in health care. Unlike physical measurement instruments, preference-based health state instruments provide health state values that are dependent on how respondents interpret the items. This study investigates how individuals with spinal cord injury (SCI) interpret mobility-related items contained within six preference-based health state instruments.MethodsSecondary analysis of focus group transcripts originally collected in Vancouver, Canada, explored individuals’ perceptions and interpretations of mobility-related items contained within the 15D, Assessment of Quality of Life 8-dimension (AQoL-8D), EQ-5D-5L, Health Utilities Index (HUI), Quality of Well-Being Scale Self-Administered (QWB-SA), and the 36-item Short Form health survey version 2 (SF-36v2). Ritchie and Spencer’s ‘Framework Approach’ was used to perform thematic analysis that focused on participants’ comments concerning the mobility-related items only.ResultsFifteen individuals participated in three focus groups (five per focus group). Four themes emerged: wording of mobility (e.g., ‘getting around’ vs ‘walking’), reference to aids and appliances, lack of suitable response options, and reframing of items (e.g., replacing ‘walking’ with ‘wheeling’). These themes reflected item features that respondents perceived as relevant in enabling them to describe their mobility, and response strategies that respondents could use when faced with inaccessible items.ConclusionInvestigating perceptions to mobility-related items within the context of SCI highlights substantial variation in item interpretation across six preference-based health state instruments. Studying respondents’ interpretations of items can help to understand discrepancies in the health state descriptions and values obtained from different instruments. This line of research warrants closer attention in the health economics and quality of life literature.

An Investigation of the Overlap Between the ICECAP-A and Five Preference-Based Health-Related Quality of Life Instruments

BackgroundThe ICEpop CAPability measure for Adults (ICECAP-A) is a measure of capability wellbeing developed for use in economic evaluations. It was designed to overcome perceived limitations associated with existing preference-based instruments, where the explicit focus on health-related aspects of quality of life may result in the failure to capture fully the broader benefits of interventions and treatments that go beyond health. The aim of this study was to investigate the extent to which preference-based health-related quality of life (HRQoL) instruments are able to capture aspects of capability wellbeing, as measured by the ICECAP-A.MethodsUsing data from the Multi Instrument Comparison project, pairwise exploratory factor analyses were conducted to compare the ICECAP-A with five preference-based HRQoL instruments [15D, Assessment of Quality of Life 8-dimension (AQoL-8D), EQ-5D-5L, Health Utilities Index Mark 3 (HUI-3), and SF-6D].ResultsData from 6756 individuals were used in the analyses. The ICECAP-A provides information above that garnered from most commonly used preference-based HRQoL instruments. The exception was the AQoL-8D; more common factors were identified between the ICECAP-A and AQoL-8D compared with the other pairwise analyses.ConclusionFurther investigations are needed to explore the extent and potential implications of ‘double counting’ when applying the ICECAP-A alongside health-related preference-based instruments.

Disability discrimination and misdirected criticism of the quality-adjusted life year framework

Whose values should count – those of patients or the general public – when adopting the quality-adjusted life year (QALY) framework for healthcare decision making is a long-standing debate. Specific disciplines, such as economics, are not wedded to a particular side of the debate, and arguments for and against the use of patient values have been discussed at length in the literature. In 2012, Sinclair proposed an approach, grounded within patient preference theory, which sought to avoid a perceived unfair discrimination against people with disabilities when using values from the general public. Key assumptions about general public values that beget this line of thinking were that ‘disabled states always tally with lower quality of life’, and the use of standardised instruments means that ‘you are forced into a fixed view of disability as a lower value state’ (Sinclair, 2012). Drawing on recent contributions to the health economics literature, we contend that such assumptions are not inherent to the incorporation of general public values for the estimation of QALYs. In practice, whether health states of people with disabilities are of ‘lower value’ is, to some extent, a reflection of the health state descriptions that members of the public are asked to value.

The impact of depression on health-related quality of life and wellbeing: identifying important dimensions and assessing their inclusion in multi-attribute utility instruments

PurposeWellbeing measures have been proposed for inclusion in economic evaluation to measure the effect of depression and compensate for shortcomings of existing multi-attribute utility instruments (MAUIs). The aims of this study were to identify dimensions of health-related quality of life (HRQoL) and wellbeing that are most affected by depression and to examine the extent to which these are captured by MAUIs.MethodsData were used from the Multi-Instrument Comparison study. Dimensions of HRQoL (SF-36v2 and AQoL-8D dimensions), capability wellbeing (ICECAP-A), and subjective wellbeing (including PWI, SWLS, and IHS) were identified that distinguished most individuals with depression from a healthy public. The extent to which these dimensions explain the content of five existing MAUIs (15D, AQoL-8D, EQ-5D-5L, HUI-3, and SF-6D) was examined using regression analyses. Additionally, the sensitivity of all MAUIs was also assessed towards depression-specific symptoms measured by DASS-21 and K-10.ResultsThe sample consisted of 917 individuals with self-reported depression and 1760 healthy subjects. Dimensions that distinguished most individuals with depression from the healthy group (effect size > 2) included AQoL-8D coping, AQoL-8D happiness, AQoL-8D self-worth, ICECAP-A, SF-36 mental health, and SF-36 social functioning. The AQoL-8D was most sensitive to the dimensions above as well as towards the depression-specific measures, the K10, DASS-S, and DASS-D.ConclusionsThis study has shown that psychosocial dimensions of HRQoL have the greatest ability to capture the impact of depression when compared with dimensions of capability wellbeing and SWB. Some MAUIs, such as the AQoL-8D, are sensitive to most distinguishing dimensions of HRQoL and wellbeing, which may obviate the need for supplementary wellbeing instruments.