Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
327608 | Journal of Psychiatric Research | 2007 | 8 Pages |
ObjectivesRecent work using classical test theory (CTT) and item response theory (IRT) has found that the self-report (QIDS-SR16) and clinician-rated (QIDS-C16) versions of the 16-item quick inventory of depressive symptomatology were generally comparable in outpatients with nonpsychotic major depressive disorder (MDD). This report extends this comparison to a less well-educated, more treatment-resistant sample that included more ethnic/racial minorities using IRT and selected classical test analyses.MethodsThe QIDS-SR16 and QIDS-C16 were obtained in a sample of 441 outpatients with nonpsychotic MDD seen in the public sector in the Texas Medication Algorithm Project (TMAP). The Samejima graded response IRT model was used to compare the QIDS-SR16 and QIDS-C16.ResultsThe nine symptom domains in the QIDS-SR16 and QIDS-C16 related well to overall depression. The slopes of the item response functions, a, which index the strength of relationship between overall depression and each symptom, were extremely similar with the two measures. Likewise, the CTT and IRT indices of symptom frequency (item means and locations of the item response functions, bi were also similar with these two measures. For example, sad mood and difficulty with concentration/decision making were highly related to the overall depression severity with both the QIDS-C16 and QIDS-SR16. Likewise, sleeping difficulties were commonly reported, even though they were not as strongly related to overall magnitude of depression.ConclusionIn this less educated, socially disadvantaged sample, differences between the QIDS-C16 and QIDS-SR16 were minor. The QIDS-SR16 is a satisfactory substitute for the more time-consuming QIDS-C16 in a broad range of adult, nonpsychotic, depressed outpatients.