Deriving utility scores from the SF-36 health instrument using Rasch analysis

Assessment of fatigue and its impact in chronic liver disease

Patient-reported outcomes (PROs), such as health-related quality of life (HRQL), are important outcome measures for patients with chronic liver diseases (CLDs). Presence of cirrhosis and advanced liver disease have been associated with worsened HRQL and fatigue. On the other hand, some patients with earlier stages of CLD also experience fatigue, causing PRO impairment. Treatment for some CLDs may improve HRQL and, sometimes, levels of fatigue. We aimed to provide an in-depth expert review of concepts related to fatigue and HRQL in patients with primary biliary cholangitis, hepatitis C virus and MASLD (metabolic dysfunction-associated steatotic liver disease). A panel of experts in fatigue and CLD reviewed and discussed the literature and collaborated to provide this expert review of fatigue in CLD. Herein, we review and report on the complexity of fatigue, highlighting that it is comprised of peripheral (neuromuscular failure, often in conjunction with submaximal cardiorespiratory function) and central (central nervous system dysfunction) causes. Fatigue and HRQL are measured using validated self-report instruments. Additionally, fatigue can be measured through objective tests (e.g. grip strength). Fatigue has deleterious effects on HRQL and one's ability to be physically active and socially engaged but does not always correlate with CLD severity. Treatments for hepatitis C virus and MASLD can improve levels of fatigue and HRQL, but current treatments for primary biliary cholangitis do not seem to affect levels of fatigue. We conclude that obtaining PRO data, including on HRQL and fatigue, is essential for determining the comprehensive burden of CLD and its potential treatments.

Suitability of the Epworth Sleepiness Scale (ESS) for Economic Evaluation: An Assessment of Its Convergent and Discriminant Validity

OBJECTIVE

To assess the suitability for use within economic evaluation of a widely used sleep-related instrument (the Epworth Sleepiness Scale [ESS]) by examining its convergent and discriminant validity with two widely used generic preference-based instruments (Short-Form 36 [SF-36] and the Assessment of Quality of Life 4 dimensions [AQoL-4D]).

METHODS

Data from a cross-section of 2,236 community-dwelling Australian men were analyzed. Convergent validity was investigated using Spearman's correlation, intraclass correlation, and modified Bland-Altman plots, while discriminant validity was examined using Kruskal Wallis tests.

RESULTS

All instruments showed good discriminant validity. The ESS was weakly correlated to the Short Form 6 dimension, or SF-6D (derived from the SF-36) and AQoL-4D utilities (r = 0.20 and r = 0.19, respectively). Correlations between ESS and SF-36/AQoL-4D dimensions measuring the same construct were all in the hypothesized directions but also weak (range of absolute r = 0.00 to 0.18). The level of agreement between the ESS and AQoL-4D was the weakest, followed by that between the ESS and SF-6D. Moderate convergent validity was seen between the utilities.

CONCLUSIONS

The lack of convergent validity between the ESS and the preference-based instruments shows that sleep-related constructs are not captured by the latter. The ESS has, however, demonstrated good discriminant validity comparable to that of the AQoL-4D and the SF-36/SF-6D and would therefore be equally useful for measuring subgroup differences within economic evaluation. We therefore recommend using the ESS within cost-effectiveness analysis as a complement to preference-based instruments in order to capture sleep-specific constructs not measured by the latter.

Reported Outcome Measures in Degenerative Cervical Myelopathy: A Systematic Review

OBJECTIVE

Degenerative cervical myelopathy [DCM] is a disabling and increasingly prevalent group of diseases. Heterogeneous reporting of trial outcomes limits effective inter-study comparison and optimisation of treatment. This is recognised in many fields of healthcare research. The present study aims to assess the heterogeneity of outcome reporting in DCM as the premise for the development of a standardised reporting set.

METHODS

A systematic review of MEDLINE and EMBASE databases, registered with PROSPERO (CRD42015025497) was conducted in accordance with PRISMA guidelines. Full text articles in English, with >50 patients (prospective) or >200 patients (retrospective), reporting outcomes of DCM were eligible.

RESULTS

108 studies, assessing 23,876 patients, conducted world-wide, were identified. Reported outcome themes included function (reported by 97, 90% of studies), complications (reported by 56, 52% of studies), quality of life (reported by 31, 29% of studies), pain (reported by 29, 27% of studies) and imaging (reported by 59, 55% of studies). Only 7 (6%) studies considered all of domains in a single publication. All domains showed variability in reporting.

CONCLUSIONS

Significant heterogeneity exists in the reporting of outcomes in DCM. The development of a consensus minimum dataset will facilitate future research synthesis.

Evaluation of a skin self examination attitude scale using an item response theory model approach

INTRODUCTION

The Skin Self-Examination Attitude Scale (SSEAS) is a brief measure that allows for the assessment of attitudes in relation to skin self-examination. This study evaluated the psychometric properties of the SSEAS using Item Response Theory (IRT) methods in a large sample of men ≥ 50 years in Queensland, Australia.

METHODS

A sample of 831 men (420 intervention and 411 control) completed a telephone assessment at the 13-month follow-up of a randomized-controlled trial of a video-based intervention to improve skin self-examination (SSE) behaviour. Descriptive statistics (mean, standard deviation, item-total correlations, and Cronbach's alpha) were compiled and difficulty parameters were computed with Winsteps using the polytomous Rasch Rating Scale Model (RRSM). An item person (Wright) map of the SSEAS was examined for content coverage and item targeting.

RESULTS

The SSEAS have good psychometric properties including good internal consistency (Cronbach's alpha = 0.80), fit with the model and no evidence for differential item functioning (DIF) due to experimental trial grouping was detected.

CONCLUSIONS

The present study confirms the SSEA scale as a brief, useful and reliable tool for assessing attitudes towards skin self-examination in a population of men 50 years or older in Queensland, Australia. The 8-item scale shows unidimensionality, allowing levels of SSE attitude, and the item difficulties, to be ranked on a single continuous scale. In terms of clinical practice, it is very important to assess skin cancer self-examination attitude to identify people who may need a more extensive intervention to allow early detection of skin cancer.

A review of the measurement properties of the 36-item short-form health survey (SF-36) to determine its suitability for use in an alcohol-dependent population

A psychometric evaluation of the 36-item short-form health survey (SF-36) was undertaken in contemporary studies to assess its suitability for use in an alcohol-dependent population. Three criteria were used to try and determine this: factor analysis, internal consistency reliability and test-retest reliability. Factor analysis revealed that it is mainly consistent with a bidimensional model, internal consistency reliability showed that it consistently provided scores above the recommended threshold and test-retest reliability of the SF-36 highlights that it too provided higher than suggested scores. A conclusion was reached recommending the SF-36 as a reliable screening tool in an alcohol-dependent population, but this is given in caution as no studies were found analysing the instrument in this population.

Estimating utilities for chronic kidney disease, using SF-36 and SF-12-based measures: challenges in a population of veterans with diabetes

PURPOSE

Using transformations of existing quality-of-life data to estimate utilities has the potential to efficiently provide investigators with utility information. We used within-method and across-method comparisons and estimated disutilities associated with increasing chronic kidney disease (CKD) severity.

METHODS

In an observational cohort of veterans with diabetes (DM) and pre-existing SF-36/SF-12 responses, we used six transformation methods (SF-12 to EQ-5D, SF-36 to HUI2, SF-12 to SF-6D, SF-36 to SF-6D, SF-36 to SF-6D (Bayesian method), and SF-12 to VR-6D) to estimate unadjusted utilities. CKD severity was staged using glomerular filtration rate estimated from serum creatinines, with the modification of diet in renal disease formula. We then used multivariate regression to estimate disutilities specifically associated with CKD severity stage.

RESULTS

Of 67,963 patients, 22,273 patients had recent-onset DM and 45,690 patients had prevalent DM. For the recent-onset group, the adjusted disutility associated with CKD derived from the six transformation methods ranged from 0.0029 to 0.0045 for stage 2; -0.004 to -0.0009 for early stage 3; -0.017 to -0.010 for late stage 3; -0.023 to -0.012 for stage 4; -0.078 to -0.033 for stage 5; and -0.012 to -0.001 for ESRD/dialysis.

CONCLUSION

Disutility did not increase monotonically as CKD severity increased. Differences in disutilities estimated using the six different methods were found. Both findings have implications for using such estimates in economic analyses.

Application of the Rasch model to develop a simplified version of a multiattribute utility measurement on attitude toward labor epidural analgesia

BACKGROUND

Valid and reliable measures based on health behavior theory, such as multiattribute utility decision theory, are essential to elucidate complex relationships between psychological factors and labor pain. In this study we aimed to use Rasch analysis to simplify a previously developed 20-item multidimensional questionnaire on attitude toward labor epidural analgesia using multiattribute utility theory.

METHODS

The Rasch analysis was performed to condense item selection categories, to exclude misfit items and persons, and to generate a unidimensional attitude toward labor epidural analgesia (ATLEA) score. Item characteristics and thresholds of rating categories in the questionnaire were also estimated. Reliability and empirical validity of the simplified version were further compared with those of the full version.

RESULTS

One hundred sixty-seven postpartum women completed the questionnaire. The original 10 rating scale categories were combined to make 4 without compromising reliability. Three respondents and 11 items were excluded because of misfit. Reliability indices of the simplified and full versions were 0.68 and 0.74, respectively. The correlation coefficient between ATLEA scores from the simplified and full versions was 0.89. Empirical validity values of ATLEA scores from the simplified and full versions for labor epidural analgesia decision, as assessed by area under the receiver operating characteristic curves, were 0.80 and 0.81, respectively.

CONCLUSIONS

We demonstrated application of the Rasch analysis to simplifying a multiattribute utility questionnaire without compromising reliability. Further study is necessary to determine whether the simplified questionnaire is valid for use in clinical practice.

Creating scenarios of the impact of COPD and their relationship to COPD Assessment Test (CAT™) scores

BACKGROUND

The COPD Assessment Test (CAT™) is a new short health status measure for routine use. New questionnaires require reference points so that users can understand the scores; descriptive scenarios are one way of doing this. A novel method of creating scenarios is described.

METHODS

A Bland and Altman plot showed a consistent relationship between CAT scores and scores obtained with the St George's Respiratory Questionnaire for COPD (SGRQ-C) permitting a direct mapping process between CAT and SGRQ items. The severity associated with each CAT item was calculated using a probabilistic model and expressed in logits (log odds of a patient of given severity affirming that item 50% of the time). Severity estimates for SGRQ-C items in logits were also available, allowing direct comparisons with CAT items. CAT scores were categorised into Low, Medium, High and Very High Impact. SGRQ items of corresponding severity were used to create scenarios associated with each category.

RESULTS

Each CAT category was associated with a scenario comprising 12 to 16 SGRQ-C items. A severity 'ladder' associating CAT scores with exemplar health status effects was also created. Items associated with 'Low' and 'Medium' Impact appeared to be subjectively quite severe in terms of their effect on daily life.

CONCLUSIONS

These scenarios provide users of the CAT with a good sense of the health impact associated with different scores. More generally they provide a surprising insight into the severity of the effects of COPD, even in patients with apparently mild-moderate health status impact.

Rasch analysis of the Patient and Observer Scar Assessment Scale (POSAS) in burn scars

PURPOSE

The Patient and Observer Scar Assessment Scale (POSAS) is a questionnaire that was developed to assess scar quality. It consists of two separate six-item scales (Observer Scale and Patient Scale), both of which are scored on a 10-point rating scale. After many years of experience with this scale in burn scar assessment, it is appropriate to examine its psychometric properties using Rasch analysis.

METHODS

Cross-sectional data collection from seven clinical trials resulted in a data set of 1,629 observer scores and 1,427 patient scores of burn scars. We examined the person-item map, item fit statistics, reliability, response category ordering, and dimensionality of the POSAS.

RESULTS

The POSAS showed an adequate fit to the Rasch model, except for the item surface area. Person reliability of the Observer Scale and Patient Scale was 0.82 and 0.77, respectively. Dimensionality analysis revealed that the unexplained variance by the first contrast of both scales was 1.7 units. Spearman correlation between the Observer Scale Rasch measure and the overall opinion of the clinician was 0.75.

CONCLUSION

The Rasch model demonstrated that the POSAS is a reliable and valid scale that measures the single-construct scar quality.

The AUSCAN subscales, AIMS-2 hand/finger subscale, and FIOHA were not unidimensional scales

OBJECTIVES

Evaluate the internal construct validity of the Australian/Canadian (AUSCAN) index for hand osteoarthritis (HOA) and identify the physical function instrument with best performance.

STUDY DESIGN AND SETTING

AUSCAN, AIMS-2 (Arthritis Impact Measurement Scale 2), and Functional Index of HOA (FIHOA) were self-completed by 209 HOA patients (mean [standard deviation] age 61.6 [5.7] years) at baseline and 128 at follow-up. Rasch analysis was performed.

RESULTS

AUSCAN pain, physical function, and stiffness subscales comprised three constructs. AUSCAN scale performance was improved after removal of "Pain at rest" from the pain scale and division of physical function into two scales of high precision and grip strength tasks. AIMS-2 hand/finger subscale and FIHOA were improved after removal of one and two items, respectively and collapse of two AIMS-2 response categories. AUSCAN physical function scale showed better targeting to the sample and higher person reliability compared with FIHOA and especially AIMS-2 because of less "severe" items concerning grip strength tasks as opposed to precision tasks.

CONCLUSION

The AUSCAN subscales, AIMS-2 hand/finger scale, and FIHOA were not unidimensional. However, deletion of misfitting items improved scale performance. The revised AUSCAN physical function and FIHOA scales are preferable for measurement of grip strength and precision tasks, respectively.

Defining value in spine care

Spinal disorders are extremely common, debilitating, and costly to the payer and to society as a whole. The rate and cost of various spinal treatments are increasing at an astonishing rate, but it is unclear whether the resulting quality of spinal care is improving. Rather than focusing solely on quality improvement measures or cost-saving measures, there is a recent emphasis on the value of health care. Defining the value of spine care depends on a standardized, accurate method of measuring outcomes and costs. It is important that the outcomes measured are patient centered and that both the outcomes and costs are measured over time with long-term follow-up. The purpose of this article is to review current methods for measuring outcomes and propose a means by which the value of spine care can be more clearly defined.