Psychometric properties of the Quick Inventory of Depressive Symptomatology (QIDS-SR) in UK primary care.

It is widely believed that severity of depressive disorder should guide treatment selection and many guidelines emphasise this factor. The Quick Inventory of Depressive Symptomatology (QID-SR16) is a self-complete measure of depression severity which includes all DSM-IV criterion symptoms for major depressive disorder. The object of this study was to assess the psychometric properties of the QIDS-SR16 in a primary care sample. Adult primary care patients completed the QIDS-SR16 and were assessed by a psychiatrist (blind to QIDS-SR16) with the 17-item Hamilton Rating Scale for Depression (GRID-HAMD). Internal consistency, homogeneity and convergent and discriminant validity of the QIDS-SR16 were assessed. Severity cut-off scores for QIDS-SR16 were assessed for convergence with HRSD-17 cut-offs. Published methods for converting scores to HRSD-17 were also assessed. Two hundred and eighty-six patients participated: mean age = 49.5 (s.d. = 13.8), 68% female, mean HRSD-17 = 12.6 (s.d. = 7.6). The QIDS-SR16 exhibited acceptable internal consistency (Cronbach's alpha = 0.86), a robust factor structure indicating one underlying dimension and correlated highly with the HRSD-17 (r = 0.79) but differed significantly in how it categorised the severity of depression relative to the HRSD-17 (Wilcoxon Signed Rank Test p < 0.001). Using published methods to convert QIDS-SR16 scores to HRSD-17 scores did not result in alignment of severity categorisation. In conclusion, psychometric properties of the QIDS-SR16 were found to be strong in terms of internal consistency, factor structure and convergent and discriminant validity. Using conventional scoring and conversion methods the scale was found not to concur with the HRSD-17 in categorising the severity of depressive symptoms.