290,784 research outputs found
Exploring the consistency of the SF-6D
Objective: The six dimensional health state short form (SF-6D) was designed to be derived from the short-form 36 health survey (SF-36). The purpose of this research was to compare the SF-6D index values generated from the SF 36 (SF-6D(SF-36)) with those obtained from the SF-6D administered as an independent instrument (SF-6D(Ind)). The goal was to assess the consistency of respondents answers to these two methods of deriving the SF-6D. Methods: Data were obtained from a sample of the Portuguese population (n = 414). Agreement between the instruments was assessed on the basis of a descriptive system and their indexes. The analysis of the descriptive system was performed by using a global consistency index and an identically classified index. Agreement was also explored by using correlation coefficients. Parametric tests were used to identify differences between the indexes. Regression models were estimated to understand the relationship between them. Results: The SF-6D(Ind) generates higher values than does the SF-6D(SF-36), There were significant differences between the indexes across sociodemographic groups. There was a significant ceiling effect in the SF-6D(Ind) a but not in the SF-6D(SF-36). The correlation between the indexes was high but less than what was anticipated. The global consistency index identified the dimensions with larger differences. Considerable differences were found in two dimensions, possibly as a result of different item contexts. Further research is needed to fully understand the role of the different layouts and the length of the questionnaires in the respondents' answers. Conclusions: The results show that as the SF-6D was designed to derive utilities from the SF-36 it should be used in this way and not as an independent instrument.Fundacao para a Ciencia e a Tecnologia (FCT
Noncompact gaugings, chiral reduction and dual sigma models in supergravity
We show that the half-maximal SU(2) gauged supergravity with topological mass
term admits coupling of an arbitrary number of n vector multiplets. The chiral
circle reduction of the ungauged theory in the dual 2-form formulation gives
N=(1,0) supergravity in 6D coupled to 3p scalars that parametrize the coset
SO(p,3)/SO(p)x SO(3), a dilaton and (p+3) axions with p < n+1. Demanding that
R-symmetry gauging survives in 6D is shown to put severe restrictions on the 7D
model, in particular requiring noncompact gaugings. We find that the SO(2,2)
and SO(3,1) gauged 7D supergravities give a U(1)_R, and the SO(2,1) gauged 7D
supergravity gives an Sp(1)_R gauged chiral 6D supergravities coupled to
certain matter multiplets. In the 6D models obtained, with or without gauging,
we show that the scalar fields of the matter sector parametrize the coset
SO(p+1,4)/SO(p+1)x SO(4), with the (p+3) axions corresponding to its abelian
isometries. In the ungauged 6D models, upon dualizing the axions to 4-form
potentials, we obtain coupling of p linear multiplets and one special linear
multiplet to chiral 6D supergravity.Comment: 41 pages, late
Interacting Chiral Gauge Fields in Six Dimensions and Born-Infeld Theory
Dimensional reduction of a self-dual tensor gauge field in 6d gives an
Abelian vector gauge field in 5d. We derive the conditions under which an
interacting 5d theory of an Abelian vector gauge field is the dimensional
reduction of a 6d Lorentz invariant interacting theory of a self-dual tensor.
Then we specialize to the particular 6d theory that gives 5d Born-Infeld
theory. The field equation and Lagrangian of this 6d theory are formulated with
manifest 5d Lorentz invariance, while the remaining Lorentz symmetries are
realized nontrivially. A string soliton with finite tension and self-dual
charge is constructed.Comment: 22 pages, latex, no figure
Exact Wave Solutions to 6D Gauged Chiral Supergravity
We describe a broad class of time-dependent exact wave solutions to 6D gauged
chiral supergravity with two compact dimensions. These 6D solutions are
nontrivial warped generalizations of 4D pp-waves and Kundt class solutions and
describe how a broad class of previously-static compactifications from 6D to 4D
(sourced by two 3-branes) respond to waves moving along one of the
uncompactified directions. Because our methods are generally applicable to any
higher dimensional supergravity they are likely to be of use for finding the
supergravity limit of time-dependent solutions in string theory. The 6D
solutions are interesting in their own right, describing 6D shock waves induced
by high energy particles on the branes, and as descriptions of the near-brane
limit of the transient wavefront arising from a local bubble-nucleation event
on one of the branes, such as might occur if a tension-changing phase
transition were to occur.Comment: 22 pages, 1 figure. Minor clarifications added. Accepted in JHE
A view from the Bridge: agreement between the SF-6D utility algorithm and the Health utilities Index
BACKGROUND: The SF-6D is a new health state classification and utility scoring system based on 6 dimensions (â6Dâ)
of the Short Form 36, and permits a ââbridgingââ transformation between SF-36 responses and utilities. The Health
Utilities Index, mark 3 (HUI3) is a valid and reliable multi-attribute health utility scale that is widely used. We
assessed within-subject agreement between SF-6D utilities and those from HUI3.
METHODS: Patients at increased risk of sudden cardiac death and participating in a randomized trial of implantable
defibrillator therapy completed both instruments at baseline. Score distributions were inspected by scatterplot and
histogram and mean score differences compared by paired t-test. Pearson correlation was computed between
instrument scores and also between dimension scores within instruments. Between-instrument agreement was by
intra-class correlation coefficient (ICC).
RESULTS: SF-6D and HUI3 forms were available from 246 patients. Mean scores for HUI3 and SF-6D were 0.61
(95% CI 0.60â0.63) and 0.58 (95% CI 0.54â0.62) respectively; a difference of 0.03 (p50.03). Score intervals for
HUI3 and SF-6D were (-0.21 to 1.0) and (0.30â0.95). Correlation between the instrument scores was 0.58 (95% CI
0.48â0.68) and agreement by ICC was 0.42 (95% CI 0.31â0.52). Correlations between dimensions of SF-6D were
higher than for HUI3.
CONCLUSIONS: Our study casts doubt on the whether utilities and QALYs estimated via SF-6D are comparable with
those from HUI3. Utility differences may be due to differences in underlying concepts of health being measured, or
different measurement approaches, or both. No gold standard exists for utility measurement and the SF-6D is a
valuable addition that permits SF-36 data to be transformed into utilities to estimate QALYs. The challenge is
developing a better understanding as to why these classification-based utility instruments differ so markedly in their
distributions and point estimates of derived utilities
What is the relationship between the minimally important difference and health state utility values? The case of the SF-6D
BACKGROUND:
The SF-6D is a new single summary preference-based measure of health derived from the SF-36. Empirical work is required to determine what is the smallest change in SF-6D scores that can be regarded as important and meaningful for health professionals, patients and other stakeholders.
OBJECTIVES:
To use anchor-based methods to determine the minimally important difference (MID) for the SF-6D for various datasets.
METHODS:
All responders to the original SF-36 questionnaire can be assigned an SF-6D score provided the 11 items used in the SF-6D have been completed. The SF-6D can be regarded as a continuous outcome scored on a 0.29 to 1.00 scale, with 1.00 indicating "full health".
Anchor-based methods examine the relationship between an health-related quality of life (HRQoL) measure and an independent measure (or anchor) to elucidate the meaning of a particular degree of change. One anchor-based approach uses an estimate of the MID, the difference in the QoL scale corresponding to a self-reported small but important change on a global scale. Patients were followed for a period of time, then asked, using question 2 of the SF-36 as our global rating scale, (which is not part of the SF-6D), if there general health is much better (5), somewhat better (4), stayed the same (3), somewhat worse (2) or much worse (1) compared to the last time they were assessed. We considered patients whose global rating score was 4 or 2 as having experienced some change equivalent to the MID. In patients who reported a worsening of health (global change of 1 or 2) the sign of the change in the SF-6D score was reversed (i.e. multiplied by minus one). The MID was then taken as the mean change on the SF-6D scale of the patients who scored (2 or 4).
RESULTS:
This paper describes the MID for the SF-6D from seven longitudinal studies that had previously used the SF-36.
CONCLUSIONS:
From the seven reviewed studies (with nine patient groups) the MID for the SF-6D ranged from 0.010 to 0.048, with a weighted mean estimate of 0.033 (95% CI: 0.029 to 0.037). The corresponding Standardised Response Means (SRMs) ranged from 0.11 to 0.48, with a mean of 0.30 and were mainly in the "small to moderate" range using Cohen's criteria, supporting the MID results. Using the half-standard deviation (of change) approach the mean effect size was 0.051 (range 0.033 to 0.066). Further empirical work is required to see whether or not this holds true for other patient groups and populations
Green-Schwarz Automorphisms and 6D SCFTs
All known interacting 6D superconformal field theories (SCFTs) have a tensor
branch which includes anti-chiral two-forms and a corresponding lattice of
string charges. Automorphisms of this lattice preserve the Dirac pairing and
specify discrete global and gauge symmetries of the 6D theory. In this paper we
compute this automorphism group for 6D SCFTs. This discrete data determines the
geometric structure of the moduli space of vacua. Upon compactification, these
automorphisms generate Seiberg-like dualities, as well as additional theories
in discrete quotients by the 6D global symmetries. When a perturbative
realization is available, these discrete quotients correspond to including
additional orientifold planes in the string construction.Comment: v2: 66 pages, 5 figures, updated references and clarifications adde
Health-state utilities in a prisoner population : a cross-sectional survey
Background: Health-state utilities for prisoners have not been described.
Methods: We used data from a 1996 cross-sectional survey of Australian prisoners (n = 734).
Respondent-level SF-36 data was transformed into utility scores by both the SF-6D and Nichol's
method. Socio-demographic and clinical predictors of SF-6D utility were assessed in univariate
analyses and a multivariate general linear model.
Results: The overall mean SF-6D utility was 0.725 (SD 0.119). When subdivided by various medical
conditions, prisoner SF-6D utilities ranged from 0.620 for angina to 0.764 for those with none/mild
depressive symptoms. Utilities derived by the Nichol's method were higher than SF-6D scores,
often by more than 0.1. In multivariate analysis, significant independent predictors of worse utility
included female gender, increasing age, increasing number of comorbidities and more severe
depressive symptoms.
Conclusion: The utilities presented may prove useful for future economic and decision models
evaluating prison-based health programs
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