"It ain't over till the fat lady sings" : A response to Cameron N. McIntosh, improving the evaluation of model fit in confirmatory factor analysis

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Minimal important differences and response shift in health-related quality of life : a longitudinal study in patients with multiple myeloma

Acknowledgements This project has been financed with the aid of EXTRA funds from the Norwegian Foundation for Health and Rehabilitation. The authors thank health-care providers at the following hospitals for recruiting patients to this study: Akershus University Hospital; Diakonhjemmet Hospital; Lovisenberg Diaconal Hospital; Oslo University Hospital, Aker; Oslo University Hospital, Ulleval; Sorlandet Hospital, Arendal; Sykehuset in Vestfold, Tonsberg; Sykehuset Innlandet, division Gjovik, Hamar, Kongsvinger and Lillehammer; Sykehuset Ostfold, Fredrikstad; Telemark Hospital, Skien; Vestre Viken HF, division Asker and Baerum, Buskerud, Kongsberg and Ringerike. Preliminary results have been presented as a paper at the ISOQOL annual meeting, New Orleans, October 2009Peer reviewedPublisher PD

Is progression-free survival associated with a better health-related quality of life in patients with lung cancer? : Evidence from two randomised trials with afatinib

Acknowledgements Medical writing assistance, supported financially by Boehringer Ingelheim, was provided by Suzanne Patel during the preparation of this article. Funding This study was supported by Boehringer Ingelheim.Peer reviewedPublisher PD

Meaning behind measurement : self-comparisons affect responses to health related quality of life questionnaires

Purpose The subjective nature of quality of life is particularly pertinent to the domain of health-related quality of life (HRQOL) research. The extent to which participants’ responses are affected by subjective information and personal reference frames is unknown. This study investigated how an elderly population living with a chronic metabolic bone disorder evaluated self-reported quality of life. Methods Participants (n = 1,331) in a multi-centre randomised controlled trial for the treatment of Paget’s disease completed annual HRQOL questionnaires, including the SF-36, EQ-5D and HAQ. Supplementary questions were added to reveal implicit reference frames used when making HRQOL evaluations. Twenty-one participants (11 male, 10 female, aged 59–91 years) were interviewed retrospectively about their responses to the supplementary questions, using cognitive interviewing techniques and semi-structured topic guides. Results The interviews revealed that participants used complex and interconnected reference frames to promote response shift when making quality of life evaluations. The choice of reference frame often reflected external factors unrelated to individual health. Many participants also stated that they were unclear whether to report general or disease-related HRQOL. Conclusions It is important, especially in clinical trials, to provide instructions clarifying whether ‘quality of life’ refers to disease-related HRQOL. Information on selfcomparison reference frames is necessary for the interpretation of responses to questions about HRQOL.The Chief Scientist Office of the Scottish Government Health Directorates, The PRISM funding bodies (the Arthritis Research Campaign, the National Association for the Relief of Paget’s disease and the Alliance for Better Bone Health)Peer reviewedAuthor final versio

Deriving a preference-based measure for cancer using the EORTC QLQ-C30 : a confirmatory versus exploratory approach

Background: To derive preference-based measures from various condition-specific descriptive health-related quality of life (HRQOL) measures. A general 2-stage method is evolved: 1) an item from each domain of the HRQOL measure is selected to form a health state classification system (HSCS); 2) a sample of health states is valued and an algorithm derived for estimating the utility of all possible health states. The aim of this analysis was to determine whether confirmatory or exploratory factor analysis (CFA, EFA) should be used to derive a cancer-specific utility measure from the EORTC QLQ-C30. Methods: Data were collected with the QLQ-C30v3 from 356 patients receiving palliative radiotherapy for recurrent or metastatic cancer (various primary sites). The dimensional structure of the QLQ-C30 was tested with EFA and CFA, the latter based on a conceptual model (the established domain structure of the QLQ-C30: physical, role, emotional, social and cognitive functioning, plus several symptoms) and clinical considerations (views of both patients and clinicians about issues relevant to HRQOL in cancer). The dimensions determined by each method were then subjected to item response theory, including Rasch analysis. Results: CFA results generally supported the proposed conceptual model, with residual correlations requiring only minor adjustments (namely, introduction of two cross-loadings) to improve model fit (increment χ2(2) = 77.78, p 75% observation at lowest score), 6 exhibited misfit to the Rasch model (fit residual > 2.5), none exhibited disordered item response thresholds, 4 exhibited DIF by gender or cancer site. Upon inspection of the remaining items, three were considered relatively less clinically important than the remaining nine. Conclusions: CFA appears more appropriate than EFA, given the well-established structure of the QLQ-C30 and its clinical relevance. Further, the confirmatory approach produced more interpretable results than the exploratory approach. Other aspects of the general method remain largely the same. The revised method will be applied to a large number of data sets as part of the international and interdisciplinary project to develop a multi-attribute utility instrument for cancer (MAUCa)

Use of methods for specifying the target difference in randomised controlled trial sample size calculations : Two surveys of trialists' practice

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Simple imputation methods were inadequate for missing not at random (MNAR) quality of life data

Acknowledgements We thank the patients who took part in the RECORD study, without whose help this study would not have been possible. The MRC funded the central organisation of RECORD, and Shire Pharmaceuticals Group plc funded the drugs, which were manufactured by Nycomed Ltd. The Health Services Research Unit is funded by the Chief Scientist Office of the Scottish Government Health Directorate. Shona Fielding is also currently funded by the Chief Scientist Office on a Research Training Fellowship (CZF/1/31). The views expressed are, however, not necessarily those of the funding body.Peer reviewedPublisher PD

Validation and Reliability Testing of the EORTC QLQ-NMIBC24 Questionnaire Module to Assess Patient-reported Outcomes in Non–Muscle-invasive Bladder Cancer

Funding/Support and role of the sponsor: Trial recruitment was facilitated within centres by the National Institute for Health Research Cancer Research Network. Pfizer provided study medication free of charge within the BOXIT trial.Peer reviewedPublisher PD

Doloplus-2, a valid tool for behavioural pain assessment?

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Combinatorial realizations of crystals via torus actions on quiver varieties

Consider Kashiwara's crystal associated to a highest weight representation of a symmetric Kac-Moody algebra. There is a geometric realization of this object using Nakajima's quiver varieties, but in many particular cases it can also be realized by elementary combinatorial methods. Here we propose a framework for extracting combinatorial realizations from the geometric picture: We construct certain torus actions on the quiver varieties and use Morse theory to index the irreducible components by connected components of the subvariety of torus fixed points. We then discuss the case of affine sl(n). There the fixed point components are just points, and are naturally indexed by multi-partitions. There is some choice in our construction, leading to a family of combinatorial models for each highest weight crystal. Applying this construction to the crystal of the fundamental representation recovers a family of combinatorial realizations recently constructed by Fayers. This gives a more conceptual proof of Fayers' result as well as a generalization to higher level. We also discuss a relationship with Nakajima's monomial crystal.Comment: 23 pages, v2: added Section 8 on monomial crystals and some references; v3: many small correction