Skip to main content

Advertisement

SpringerLink
Log in

Reducing the Floor Effect in the SF-6D: A Feasibility Study

  • Published:
Applied Research in Quality of Life Aims and scope Submit manuscript

An Erratum to this article was published on 13 November 2015

Abstract

The SF-6D suffers from a floor effect where for patient groups in severe health a significant number of patients report the lowest level of health possible for some dimensions, meaning the SF-6D cannot capture a deterioration in health for these patients. This paper presents a feasibility study aimed at reducing this floor effect. A modified SF-6D classification system was proposed that incorporated an additional level in each of the physical functioning and role limitations dimensions. The modified classification system was valued by a Portuguese general population sample (n = 140) using the Portuguese SF-6D protocol. A sample of 82 health states were valued and several regression models were estimated to produce preference weights to predict health state values for all states defined by the modified classification system. Estimations at the individual level were performed using 950 health state valuations. Models were analyzed in terms of logical consistency of coefficients, overall fit and predictive ability and were compared to Portuguese SF-6D models. The additional severity levels included in the modified classification system have significant decrements in health state values. These additional severity levels do not significantly impact on the modelled preference weights (the regression coefficients) of other levels across all dimensions. This feasibility study modified the SF-6D to reduce the floor effect. This study presents one option and further research in this area is encouraged.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1

Similar content being viewed by others

References

  • Baum, C. (2006). An introduction to modern econometrics using stata (1st ed.). USA: Stata.

    Google Scholar 

  • Brazier, J., & Roberts, J. (2004). The estimation of a preference-based measure of health from the SF-12. Medical Care, 42(9), 851–859.

    Article  Google Scholar 

  • Brazier, J., Roberts, J., & Deverill, M. (2002). The estimation of a preference-based measure of health from the SF-36. Journal of Health Economics, 21, 271–292.

    Article  Google Scholar 

  • Brazier, J., Roberts, J., Tsuchiya, A., & Busschbach, J. (2004). A comparison of the EQ-5D and SF-6D across seven patient groups. Health Economics, 13, 873–884.

    Article  Google Scholar 

  • Brazier, J., Roberts, J., Platts, M., & Zoellner, Y. (2005). Estimating a preference-based index for a menopause specific health quality of life questionnaire. Health and Quality of Life Outcomes, 3, 13.

    Article  Google Scholar 

  • Brazier, J., Fukahara, S., Roberts, J., Kharroubi, S., Yamamoto, Y., Ikeda, S., et al. (2009). Estimating a preference-based index from the Japanese SF-36. Journal of Clinical Epidemiology, 62(12), 1323–1331.

    Article  Google Scholar 

  • Ferreira, L., & Ferreira, P. (2008). Quality of life in patients with cataracts. Oftalmologia, 32, 159–175 [article in Portuguese].

    Google Scholar 

  • Ferreira, L., Ferreira, P., & Baleiro, R. (2008a). Quality of life in patients with rheumatoid arthritis. Acta Reumatológica Portuguesa, 33(3), 341–342 [article in Portuguese].

    Google Scholar 

  • Ferreira, L., Ferreira, P., Pereira, L., & Brazier, J. (2008b). An application of the SF-6D to create health values in Portuguese working age adults. Journal of Medical Economics, 11(2), 215–233.

    Google Scholar 

  • Ferreira, P., Ferreira, L., & Pereira, L. (2008c). How consistent are health utility values? Quality of Life Research, 17(7), 1031–1042.

    Article  Google Scholar 

  • Ferreira, L., Brito, U., & Ferreira, P. (2010a). Quality of life in asthma patients. Portuguese Journal of Pulmonology, XV(1), 23–55.

    Google Scholar 

  • Ferreira, L., Ferreira, P., Pereira, L., Brazier, J., & Rowen, D. (2010b). A Portuguese value set for the SF-6D. Value in Health, 13(5), 624–630.

    Article  Google Scholar 

  • Fisk, J., Brown, M., Sketris, I., Metz, L., Murray, T., & Stadnyk, K. (2005). A comparison of health utility measures for the evaluation of multiple sclerosis treatments. Journal of Neurology, Neurosurgery, and Psychiatry, 76, 58–63.

    Article  Google Scholar 

  • Gerard, K., Nicholson, T., Mulle, M., Mehta, R., & Roderick, P. (2004). EQ-5D versus SF-6D in an older, chronically Ill patient group. Applied Health Economics and Health Policy, 3(2), 91–102.

    Article  Google Scholar 

  • Harrison, M. J., Davies, L. M., Bansback, N. J., McCoy, M. J., Verstappen, S. M., Watson, K., et al. (2009). The comparative responsiveness of the EQ-5D and SF-6D to change in patients with inflammatory arthritis. Quality of Life Research, 18, 1195–1205.

    Article  Google Scholar 

  • Hatoum, H., Brazier, J., & Ahkras, K. (2004). Comparison of the HU13 with the SF-36 preference based single index in a clinical setting. Value in Health, 7, 602–609.

    Article  Google Scholar 

  • Lamers, L., Bouwmans, C., van Straten, A., Donker, M., & Hakkaart, L. (2006). Comparison of EQ-5D and SF-6D utilities in mental health patients. Health Economics, 15(11), 1229–1236.

    Article  Google Scholar 

  • Liang, K.-Y., & Zeger, S. (1986). Longitudinal data analysis using generalized linear models. Biometrika, 73, 13–22.

    Article  Google Scholar 

  • Longworth, L., & Bryan, S. (2003). An empirical comparison of EQ-5D and SF-6D in liver transplant patients. Health Economics, 12(12), 1061–1067.

    Article  Google Scholar 

  • McCabe, C., Stevens, K., Roberts, J., & Brazier, J. (2005). Health state values for the HUI2 descriptive system: Results from a UK survey. Health Economics, 14, 231–244.

    Article  Google Scholar 

  • Pan, W. (2001). Akaike‘s information criterion in generalized estimating equations. Biometrics, 57, 120–125.

    Article  Google Scholar 

  • Petrou, S., & Hockley, C. (2005). An investigation into the empirical validity of the EQ-5D and SF-6D based on hypothetical preferences in a general population. Health Economics, 14(11), 1169–1189.

    Article  Google Scholar 

  • Stavem, K., Frøland, S., & Hellum, K. (2005). Comparison of preference-based utilities of the 15D, EQ-5D and SF-6D in patients with HIV/AIDS. Quality of Life Research, 14, 971–980.

    Article  Google Scholar 

  • Szende, A., Svensson, K., Ståhl, E., Mészáros, A., & Berta, G. (2004). Psychometric and utility-based measures of health status of asthmatic patients with different disease control level. PharmacoEconomics, 22(8), 537–547.

    Article  Google Scholar 

  • Szende, A., Leidy, N., Ståhl, E., & Svensson, K. (2009). Estimating health utilities in patients with asthma and COPD: Evidence on the performance of EQ-5D and SF-6D. Quality of Life Research, 18, 267–272.

    Article  Google Scholar 

  • Zeger, S. L., & Liang, K.-Y. (1986). Longitudinal data analysis for discrete and continuous outcomes. Biometrics, 42, 121–130.

    Article  Google Scholar 

Download references

Acknowledgment

The authors thank the anonymous referees for their constructive comments and suggestions that have considerably improved the paper. The authors thank the support from the Foundation for Science and Technology (FCT), Portugal.

Author information

Authors and Affiliations

  1. School of Management, Hospitality and Tourism, University of the Algarve, Campus da Penha, 8005–139, Faro, Portugal

    Lara N. Ferreira & Luis N. Pereira

  2. Faculty of Economics, University of Coimbra, Av. Dias da Silva, 165, 3004–512, Coimbra, Portugal

    Pedro L. Ferreira

  3. Centre for Health Studies & Research, University of Coimbra, Coimbra, Portugal

    Lara N. Ferreira & Pedro L. Ferreira

  4. Research Centre for Spatial and Organizational Dynamics, University of the Algarve, Faro, Portugal

    Luis N. Pereira

  5. School of Health and Related Research, University of Sheffield, Regent Court, 30 Regent Street, Sheffield, S1 4DA, United Kingdom

    Donna Rowen

Authors
  1. Lara N. Ferreira
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Pedro L. Ferreira
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Luis N. Pereira
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Donna Rowen
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Lara N. Ferreira.

Additional information

An erratum to this article is available at http://dx.doi.org/10.1007/s11482-015-9440-9.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Ferreira, L.N., Ferreira, P.L., Pereira, L.N. et al. Reducing the Floor Effect in the SF-6D: A Feasibility Study. Applied Research Quality Life 7, 193–208 (2012). https://doi.org/10.1007/s11482-011-9149-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s11482-011-9149-3

Keywords

Search

Navigation