Objective We sought to evaluate the validity of the Spanish language version of the patient health questionnaire-9 (PHQ-9) depression scale in a large sample of pregnant Peruvian women using Rasch item response theory (IRT) approaches. We further sought to examine the appropriateness of the response formats, reliability and potential differential item functioning (DIF) by maternal age, educational attainment and employment status. Methods This cross-sectional study was conducted among 1520 pregnant women in Lima, Peru. A structured interview was used to collect information on demographic characteristics and PHQ-9 items. Data from the PHQ-9 were fitted to the Rasch IRT model and tested for appropriate category ordering, the assumptions of unidimensionality and local independence, item fit, reliability and presence of DIF. Results The Spanish language version of PHQ-9 demonstrated unidimen...

Objective: We sought to evaluate the psychometric properties of two widely used screening scales: the Patient Health Questionnaire (PHQ-9) and Edinburgh Postnatal Depression Scale (EPDS) among pregnant Peruvian women. Methods: This cross-sectional study included 1517 women receiving prenatal care from February 2012 to March 2013. A structured interview was used to collect data using PHQ-9 and EPDS. We examined reliability, construct and concurrent validity between two scales using internal consistency indices, factor structures, correlations, and Cohen׳s kappa. Results: Both scales had good internal consistency (Cronbach׳s alpha>0.8). Correlation between PHQ-9 and EPDS scores was fair (rho=0.52). Based on exploratory factor analysis (EFA), both scales yielded a two-factor structure. EFA including all items from PHQ-9 and EPDS yielded four factors, namely, "somatization", "depression an...