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Open Access Study protocol

Predicting the onset and persistence of episodes of depression in primary health care. The predictD-Spain study: Methodology

Juan Ángel Bellón1*, Berta Moreno-Küstner2, Francisco Torres-González3, Carmen Montón-Franco4, María Josefa GildeGómez-Barragán5, Marta Sánchez-Celaya6, Miguel Ángel Díaz-Barreiros7, Catalina Vicens8, Juan de Dios Luna9, Jorge A Cervilla3, Blanca Gutierrez3, María Teresa Martínez-Cañavate10, Bárbara Oliván-Blázquez11, Ana Vázquez-Medrano5, María Soledad Sánchez-Artiaga12, Sebastia March13, Emma Motrico2, Victor Manuel Ruiz-García2, Paulette Renée Brangier-Wainberg14, María del Mar Muñoz-García3, Irwin Nazareth15, Michael King16 and the predictD group

Author Affiliations

1 Departamento de Medicina Preventiva, Universidad de Málaga; Unidad de Investigación de Atención Primaria de Málaga (redIAPP, grupo SAMSERAP), Centro de Salud El Palo, Spain

2 Facultad de Psicología. Universidad de Málaga; Fundación IMABIS; Distrito Sanitario Málaga. Unidad de Investigación de Atención Primaria de Málaga (redIAPP, grupo SAMSERAP), Spain

3 Departamento de Psiquiatría y Medicina legal, Universidad de Granada; Grupo Andaluz de Investigación en Salud Menta, Granada, Spain

4 Departamento de Medicina y Psiquiatría, Universidad de Zaragoza; Centro de Salud Casablanca. (redIAPP, grupo Aragón), Zaragoza, Spain

5 Servicio Riojano de la Salud; Unidad Docente de Medicina Familiar y Comunitaria de La Rioja, Logroño, La Rioja, Spain

6 Servicio Madrileño de Salud; Área I de Atención Primaria, Unidad Docente de Medicina Familiar y Comunitaria, Madrid, Spain

7 Servicio Canario de Salud, Gerencia de Atención Primaria de Gran Canaria, Centro de Salud Vecindario, Las Palmas, Spain

8 Instituto Balear de la Salud; Unidad Docente de Medicina Familiar y Comunitaria de Mallorca, Centro de Salud son Serra-La Vileta, Palma de Mallorca, Illes Balears, Spain

9 Departamento de Bioestadística (redIAPP, grupo SAMSERAP), Universidad de Granada, Spain

10 Unidad Docente de Medicina Familiar y Comunitaria de Granada (redIAPP, grupo SAMSERAP), Spain

11 Instituto Aragonés de Ciencias de la Salud, Unidad de Investigación de Atención Primaria (redIAPP, grupo Aragón), Zaragoza, Spain

12 Servicio Madrileño de Salud, Área 6 de Atención Primara, Centro de Salud Condes de Barcelona-Boadilla, Madrid, Spain

13 Instituto Balear de la Salud, Unidad de Investigación de Atención Primaria de Baleares (redIAPP, grupo Baleares), Mallorca, Spain

14 Servicio Andaluz de Salud, Distrito Sanitario Málaga. Unidad de Investigación de Atención Primaria de Málaga (redIAPP, grupo SAMSERAP), Spain

15 Medical Research Council General Practice Research Framework, London, UK

16 Department of Mental Health Sciences, UCL, London, UK

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BMC Public Health 2008, 8:256  doi:10.1186/1471-2458-8-256

Published: 25 July 2008

Abstract

Background

The effects of putative risk factors on the onset and/or persistence of depression remain unclear. We aim to develop comprehensive models to predict the onset and persistence of episodes of depression in primary care. Here we explain the general methodology of the predictD-Spain study and evaluate the reliability of the questionnaires used.

Methods

This is a prospective cohort study. A systematic random sample of general practice attendees aged 18 to 75 has been recruited in seven Spanish provinces. Depression is being measured with the CIDI at baseline, and at 6, 12, 24 and 36 months. A set of individual, environmental, genetic, professional and organizational risk factors are to be assessed at each follow-up point. In a separate reliability study, a proportional random sample of 401 participants completed the test-retest (251 researcher-administered and 150 self-administered) between October 2005 and February 2006. We have also checked 118,398 items for data entry from a random sample of 480 patients stratified by province.

Results

All items and questionnaires had good test-retest reliability for both methods of administration, except for the use of recreational drugs over the previous six months. Cronbach's alphas were good and their factorial analyses coherent for the three scales evaluated (social support from family and friends, dissatisfaction with paid work, and dissatisfaction with unpaid work). There were 191 (0.16%) data entry errors.

Conclusion

The items and questionnaires were reliable and data quality control was excellent. When we eventually obtain our risk index for the onset and persistence of depression, we will be able to determine the individual risk of each patient evaluated in primary health care.