Validation of a survey tool for use in cross-cultural studies
There is a need for tools to measure the information patients need in order for healthcare professionals in general, and particularly pharmacists, to communicate effectively and play an active part in the way patients manage their medicines. Previous research has developed and validated constructs to measure patients’ desires for information and their perceptions of how useful their medicines are. It is important to develop these tools for use in different settings and countries so that best practice is shared and is based on the best available evidence.
Objectives: this project sought to validate of a survey tool measuring the “Extent of Information Desired” (EID), the “Perceived Utility of Medicines” (PUM), and the “Anxiety about Illness” (AI) that had been previously translated for use with Portuguese patients.
Methods: The scales were validated in a patient sample of 596: construct validity was explored in Factor analysis (PCA) and internal consistency analysed using Cronbach’s alpha. Criterion validity was explored correlating scores to the AI scale and patients’ perceived health status. Discriminatory power was assessed using ANOVA. Temporal stability was explored in a sub-sample of patients who responded at two time points, using a T-test to compare their mean scores.
Results: Construct validity results indicated the need to remove 1 item from the Perceived Harm of Medicines (PHM) and Perceived Benefit of Medicines (PBM) for use in a Portuguese sample and the abandon of the tolerance scale. The internal consistency was high for the EID, PBM and AI scales (alpha>0.600) and acceptable for the PHM scale (alpha=0.536). All scales, except the EID, were consistent over time (p>0.05; p<0.01). All the scales tested showed good discriminatory power. The comparison of the AI scale with the SF-36 indicated good criterion validity (p<0.05).
Conclusion: The translated tool was valid and reliable in Portuguese patients- excluding the Tolerance scale. Some of the scales may benefit from further refinement, such as the PHM subscale.
2. Duggan C, Bates I. Development and evaluation of a survey tool to explore patients' perceptions of their prescribed drugs and need for drug information. Int J Pharm Pract 2000; 8(1): 42-52.
3. Duggan C, Bates I, Sturman S, Andersson E, Astrom K, Carlsson J. Validation of a 'desire for information' scale. Int J Pharm Pract. 2002;10(1):31-37.
4. PCNE. Pharmaceutical Care Network Europe. Available at www.pcne.org assessed 22/05/2006.
5. Instituto Nacional de Estatística. 2003, "Recenseamento Geral da População e Habitação (2001) - Resultados Definitivos." Lisboa. Data File ("General Licensing of the Population and Housing - Final Results") (original report in Portuguese).
6. DeVellis RF. Factor analysis. Scale development, theory and applications. London: SAGE Publications, 2003: 102-137.
7. Costa F, Couto S, Ferreira AP, et al. 2005a, "Hypertensive patients' perceptions about prescribed medicines. Proceedings of the FIP Congress (Abstract 108; CPS-P-083). Presented at the FIP Congress 2005.
8. Ministério da Educação. Portaria. Diário da República Portuguesa. 27-5-2005. n º 41/2005 ("Education Ministry. Law ") (original in Portuguese).
9. Costa FA, Duggan C, Bates I. A systematic approach to cross-cultural adaptation of survey tools. Pharm Pract. 2007;5(3):115-124.
10. Coelho R, Ramos E, Prata J, Barros H. Psychosocial indexes and cardiovascular risk factors in a community sample. Psychother Psychosom. 2000;69(5):261-74.
11. Horne R, Weinman J, Hankins M. The beliefs about medicines questionnaire: the development and evaluation of a new method for assessing the cognitive representation of medication. Psychol Health 1999;14:1-24.