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


CONCLUSIONS
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.
Bellón
Juan Angel
JA
Departamento de Medicina Preventiva, Universidad de Málaga; Unidad de Investigación de Atención Primaria de Málaga (redIAPP, grupo SAMSERAP), Centro de Salud El Palo, Spain. JABELLON@terra.es
Moreno-Küstner
Berta
B
Torres-González
Francisco
F
Montón-Franco
Carmen
C
GildeGómez-Barragán
María Josefa
MJ
Sánchez-Celaya
Marta
M
Díaz-Barreiros
Miguel Angel
MA
Vicens
Catalina
C
de Dios Luna
Juan
J
Cervilla
Jorge A
JA
Gutierrez
Blanca
B
Martínez-Cañavate
María Teresa
MT
Oliván-Blázquez
Bárbara
B
Vázquez-Medrano
Ana
A
Sánchez-Artiaga
María Soledad
MS
March
Sebastia
S
Motrico
Emma
E
Ruiz-García
Victor Manuel
VM
Brangier-Wainberg
Paulette Renée
PR
Del Mar Muñoz-García
María
M
Nazareth
Irwin
I
King
Michael
M
D000293:Adolescent; D000328:Adult; D000368:Aged; D003866:Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology; D005163:Factor Analysis, Statistical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011320:Primary Health Care; D011446:Prospective Studies; D012008:Recurrence; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012959:Socioeconomic Factors; D013030:Spain / Q000453:epidemiology; D011795:Surveys and Questionnaires / Q000592:standards*