The reliability and validity of the SF-8 with a conflict-affected population in northern Uganda
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BioMed Central
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Research
The reliability and validity of the SF-8 with a conflict-affected population in northern Uganda Bayard Roberts*1, John Browne2, Kaducu Felix Ocaka3, Thomas Oyok2 and Egbert Sondorp1 Address: 1Conflict and Health Programme, Health Policy Unit, Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, UK, 2Health Services Research Unit, Department of Public Health and Policy, London School of Hygiene and Tropical Medicine, UK and 3Faculty of Medicine, Gulu University, PO Box 166, Gulu, Uganda Email: Bayard Roberts* - [email protected]; John Browne - [email protected]; Kaducu Felix Ocaka - [email protected]; Thomas Oyok - [email protected]; Egbert Sondorp - [email protected] * Corresponding author
Published: 2 December 2008 Health and Quality of Life Outcomes 2008, 6:108
doi:10.1186/1477-7525-6-108
Received: 21 March 2008 Accepted: 2 December 2008
This article is available from: http://www.hqlo.com/content/6/1/108 © 2008 Roberts et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: The SF-8 is a health-related quality of life instrument that could provide a useful means of assessing general physical and mental health amongst populations affected by conflict. The purpose of this study was to test the validity and reliability of the SF-8 with a conflict-affected population in northern Uganda. Methods: A cross-sectional multi-staged, random cluster survey was conducted with 1206 adults in camps for internally displaced persons in Gulu and Amuru districts of northern Uganda. Data quality was assessed by analysing the number of incomplete responses to SF-8 items. Response distribution was analysed using aggregate endorsement frequency. Test-retest reliability was assessed in a separate smaller survey using the intraclass correlation test. Construct validity was measured using principal component analysis, and the Pearson Correlation test for item-summary score correlation and inter-instrument correlations. Known groups validity was assessed using a two sample t-test to evaluates the ability of the SF-8 to discriminate between groups known to have, and not have, physical and mental health problems. Results: The SF-8 showed excellent data quality. It showed acceptable item response distribution based upon analysis of aggregate endorsement frequencies. Test-retest showed a good intraclass correlation of 0.61 for PCS and 0.68 for MCS. The principal component analysis indicated strong construct validity and concurred with the results of the validity tests by the SF-8 developers. The SF-8 also showed strong construct validity between the 8 items and PCS and MCS summary score, moderate inter-instrument validity, and strong known groups validity. Conclusion
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