Exploring the consistency of the SF-6Dv2 in a breast cancer population

ABSTRACT

Background: Short-Form Six-Dimension version 2 (SF-6Dv2) is a multi-attribute utility instrument that can be used in combination with the SF-36v2 (SF-6Dv2_SF-36) or as an independent instrument in two forms: six questions (SF-6Dv2_ind-6) and 10 questions (SF-6Dv2_ind-10). The purpose of this research was to assess the consistency between the results of the SF-6Dv2_ind-6 and the SF-6Dv2_SF-36 in patients with breast cancer.

Research design and methods: This cross-sectional study was carried out on 418 patients with breast cancer. The degree of agreement between the descriptive systems of instruments was calculated using Spearman’s correlation coefficient, global consistency index (GCI), and identically classified index (ICI).

Results: The average size of the Spearman’s correlation coefficients between the descriptive systems of instruments was higher than 0.5. The results of the GCI revealed that the level of agreement between dimensions of the two instruments had a mean of 64.9 (range 32.45–86.8). The SF-6Dv2_SF-36 generates statistically higher values than does the SF-6Dv2_ind-6, and mean difference between the two instruments was 0.087 for model 3 and 0.027 for model 10.

Conclusions: This study provided evidence that the SF-6Dv2_SF-36 and the SF-6Dv2_ind-6 may produce different answers from patients with breast cancer and lead to a small difference in utility values.

KEYWORDS:

• Consistency
• SF-6Dv2
• breast cancer
• Iran

Acknowledgments

The authors are grateful to the chemotherapy, radiography, and surgery wards of Imam Khomeini Cancer Institute for their valuable collaboration in the present study.

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

Reviewers disclosure

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Authors’ contributions

Conceptualization: H.A. and H.S.; Methodology: H.A. and T.G.P.; Formal Analysis: H.A. and T.G.P.; Data Curation: H.A.; Writing—Original Draft Preparation: H.A. and H.S.; Writing—Review and Editing: H.A.,T.G.P., and H.S.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the national research committee (the Imam Khomeini Cancer Institute + IR.TUMS.SPH.REC. 1396.4880) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all patients included in the study.

Additional information

Funding

This study was funded by the Imam Khomeini Cancer Institute (registration number: 97-01-51-37445).