Frequently asked questions

What is available from this website?

Programmes that convert your SF-36 or SF-12 data into an SF-6D health state and corresponding utility score for each observation in your dataset.

What do the programmes do?

The programme will generate for each row of your dataset the six dimension scores of the SF-6D, the six digit health state and a utility value anchored at 1 for full health and 0 for dead.

What is the SF-6D?

The SF-6D is a generic preference-based single index measure of health that can be used to generate QALYs and hence which can be used in cost-utility analysis.

What types of programmes are available?

There are excel, SPSS and SAS programmes available to convert SF-36 data into SF-6D data and there are SPSS and SAS programmes available to convert SF-12 data into SF-6D.

All programmes generate the SF-6D utility score estimated using a set of parametric preference weights obtained from a sample of the general population using the recognised valuation technique of standard gamble. In addition a new excel programme is now available from the University of Sheffield to convert SF-36 data into the SF-6D utility score estimated using a set of non-parametric Bayesian preference weights. These nonparametric preference weights are an improvement on the parametric preference weights as the nonparametric model has many advantages over the conventional parametric random effects model which is reflected in improvements in the predictive ability of the model. For further details see Kharroubi et al. (2007).

Furthermore a new excel programme is available to convert SF-36 data into the SF-6D utility score estimated using a set of preference weights obtained using an ordinal valuation technique for a sample of the general population. The estimates using ordinal data represent an alternative value set based on a different valuation technique which produces estimates that are comparable to estimates produced using standard gamble data. For further details see McCabe et al. (2006).

What do I need to include in my study to use these programmes?

The programmes which are available from our website derive the SF-6D from either the SF-12 or the SF-36 and therefore to use these algorithms you need to include the SF-12 or SF-36 in your study. Refer to Optum Insight for details on these. These consist of 12 or 36 questions about the individual´s health where the individual chooses an option from a list of responses.

Do you provide a licence for the SF-36 and SF-12?

Refer to Optum Insight for details on these.

Do I need to include a valuation in my study?

No. You need to include either the SF-12 or the SF-36 to use these programmes. These do not involve a valuation study or ranking. The programmes which are available from our website use already existing utility values from the valuation study described in Brazier and Roberts (2004).

Is it possible to use the SF-6D alone in a study, rather than using the SF-36 or SF-12 and converting this into the SF-6D?

It is theoretically possible but not generally recommended. The data will be of limited use if only the SF-6D is included in a study as there is no conversion from the SF-6D to the SF-36 or SF-12. Furthermore the algorithms are based on the SF-6D derived from the SF-36 and we have no evidence whether this equals a directly administered SF-6D.

Can I use the SF-6D algorithm for a different study other than the study described in the initial application?

No. You need a licence agreement for each study for which you use the SF-6D algorithm.

How does the SF-6D generate preference scores?

The SF-6D comes with a set of preference weights obtained from a sample of the general population in the UK using the recognised valuation technique of standard gamble. Members of the general population in the UK were asked to value a selection of health states from which a model has been estimated to predict all the health states described by the SF-6D.

Is there a written document outlining the process for converting the SF-36 data to SF-6D scores?

Instructions are available for each of the programmes available but these do not outline how the process can be done using a different software package. We currently have algorithms available for use on SF-36 data in SAS, SPSS and excel, and for SF-12 data in SAS and SPSS.

Can I use these programmes for a study outside the UK?

The SF-6D utility score is generated using preference weights obtained from a sample of the general population in the UK. The UK population may have different preferences to non-UK populations.

Are there SF-6D preference scores available for other countries?

There is emerging evidence that standard gamble health state values differ between countries for SG, so it is often important to have local valuations. SF-6D preference scores are available for Australia, Brazil, Hong Kong, Japan, Portugal and Singapore. See below for details of who to contact for further information.

References

Brazier, JE, Roberts, JR,. The estimation of a preference-based index from the SF-12. Medical Care, 2004;42(9):851-859.
Kharroubi, S, Brazier, JE, Roberts, JR, et al. Modelling SF-6D health state preference data using a nonparametric Bayesian method. Journal of Health Economics, 2007;26(3):597-612.
McCabe, C, Brazier, JE, Gilks, P, et al. Using rank data to estimate health state utility models. Journal of Health Economics, 2006;25(3):418-431.