The creation and validation of the Jamaica personality disorder inventory

OBJECTIVE: To describe the creation and validation of the Jamaica Personality Disorder Inventory (JPDI) screening questionnaire. METHOD: Using the phenomenological triad of power management, dependency and psychosexual issues, drafts of the JPDI were piloted on patients from psychiatric and medical wards. The JPDI consisted of 38 close-ended, yes/no questions. Validation was conducted in a sample of 200 patients, using the International Personality Disorder Examination-Screening Instrument (IPDE-S), the Brief Screen for Depression and consultant psychiatrists' Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) personality disorder interview. Construct validity was assessed through principal component factor analysis; Spearman correlation was used to assess criterion-related and discriminant validity; Cronbach's alpha was used to assess reliability of the entire scale as well as the resulting factors. The Multitrait Multimethod Matrix (MTMM) was used to assess discriminant and construct validity. RESULTS: Factor analysis revealed eight clusters consisting of 30 of the 38 questions, which had close congruence with the clinical triad. Cronbach's alpha for the entire scale was α = 0.79, ranging from a high 0.70 to 0.82 to low 0.63 to 0.45. The JPDI exhibited a sensitivity of 95.06% and a specificity of 67.71%. Significant correlation of scores for the JPDI and IPDE-S (r = 0.432, p = 0.000) and the JPDI and the DSM IV-TR diagnosis (r = 0.598, p = 0.000) established concurrent validity for the JPDI. Correlations (r = 0.293, p = 0.000) suggested that the JPDI possessed predictive validity. The complete sample matrix of the MTMM provided evidence of both convergent and discriminant validity, and thereby, construct validity. CONCLUSION: The JPDI demonstrated reliability, and criterion-related and discriminant validity.