New cut-off points of PHQ-9 and its variants, in Costa Rica: a nationwide observational study.

The PHQ-9 questionnaire is a screening test worldwide used to measure depression. But it cannot be used in Costa Rica, due to the fact that it has not previously been validated for its population. The present study aims to show the validation of the PHQ-9 questionnaire and its variants (PHQ-2, PHQ-4, PHQ-8) in a population sample of adults residing in Costa Rica. A sample was collected (n = 1162) using a self-administered questionnaire. Confirmatory Factor Analysis (CFA), Receiver Operating Characteristic (ROC) curve, and Multiple Group Confirmatory Factor Analysis (MGCFA) were tested. One factor was found that explained 73.33% of the variance with excellent internal consistency (α = 0.928). Goodness-of-fit measures were adequate (RMSEA = 0.107; CFI = 0.948), as was diagnostic power at a cut-off of 10 (78.60 for Sensitivity and 27.95 for 1-Specificity). External validation indices were good (r = 0.843 with GAD-7, r = - 0.647 with RS14, and r = 0.301 with FCV19S), and the model showed invariance by sex (∆χ2 = 27.90; df = 27; p < 0.001). Additionally, new cut-off points were proposed for PHQ-9 and its variants for Costa Rican male, female, and general populations. The PHQ-9 and its variants (PHQ-2, 4, and 8) are valid tools for detecting depression (and anxiety for PHQ-4) in Costa Rican population. In addition, new cut-off points differentiated by sex are proposed.

Seven methods to determine the dimensionality of tests: application to the General Self-Efficacy Scale in twenty-six countries.

BACKGROUND: One of the most important concepts within Cognitive Social Theory as framed by Bandura is the perceived self-efficacy; this concept became widespread in 1981 when Mathias Jerusalem and Ralf Schwarzer, using 10 items, established a one-dimensional and universal construct of this scale. The main purpose of this study is to show that the General Self-Efficacy Scale (GSE) is not a one-dimensional and universal construct, as is currently assumed. METHOD: The data from 19,719 people from 26 countries were analyzed. In order to identify and understand invariance we applied seven multivariate statistical techniques. RESULTS: The findings suggest the existence of a multidimensional structure and differential item functioning by country. Insofar as there is differential item functioning by country and it is not possible to universalize it, and there are several items on the scale that statistically constitute additional factors. The results confirm that the self-efficacy construct is neither universal nor unidimensional. CONCLUSIONS: A psychometric instrument must be valued and used with great care; the one in question is being used in a generalized way.