Determining Test-Retest Reliability and Internal Consistency of the Persian Version of Personality Inventory for Diagnostic and Statistical Manual of Mental Disorders-5th Edition (PID-5) among Medical Students and Patients with Psychiatric Disorders

Given the need for access to reliable diagnostic instruments of mental disorders in Persian language, the present study was designed to translate and determine the reliability and internal consistency of the Personality Inventory for Diagnostic and Statistical Manual of Mental Disorders-5th Edition (PID-5) instrument.
Research sample was selected based on non-random (convenience) method for medical students (healthy population) and patients with personality disorder. After translating PID-5 via forward and backward translation method, test-retest reliability (10-20 days period) and internal consistency of the instrument were determined. This study was conducted in Hazrat-Rasoul Hospital, Iran Psychiatry Hospital and Tehran Psychiatric Institute, Tehran, Iran, during the year 2015. Questionnaires were self-reported and interviews were done by well-trained psychiatry residents.
Findings: Totally, 217 individuals were assessed (114 healthy volunteers and 103 patients with personality disorders). Of 25 surveyed facets, eccentricity had the highest Cronbach's alpha coefficient. The lowest alpha was seen for suspiciousness. Overall, in 22 facets from all 25 facets, alpha coefficients were higher than 0.700. To assess test-retest reliability, 28 persons of the medical students group completed the questionnaire for the second time. The correlation coefficient between the two measures in three facets (irresponsibility, perceptual dysregulation and rigid perfectionism) was between 0.800 and 0.900. In other aspects, the correlation coefficient between the two measures was higher than 0.900.
The Persian version of PID-5 instrument had good test-retest reliability (r = 0.829 to 0.944) in a short time (about two weeks) and its internal consistency was desirable (Cronbach's alpha = 0.697 to 0.944).