The integral inventory for depression, a new, self-rated clinimetric instrument for the emotional and painful dimensions in major depressive disorder

Abstract

Objective. To assess the reliability and validity of the Integral Inventory for Depression (IID) scale using post hoc analyses of data from a multi-country study (ClinicalTrials.gov: NCT00561509) of patients with major depressive disorder (MDD). Methods. Patients (N = 1629) completed the IID (comprising two separate dimensions for emotional and physically painful symptoms; maximum score of 65) and a reference scale (16-item Quick Inventory of Depressive Symptomatology Self-Report) at baseline and at follow-up (8 and 24 weeks). Physicians rated MDD symptoms using the Clinical Global Impressions of Severity scale at each visit. Inter-item correlation, internal consistency, external validity, factor structure, and exploratory analysis of an optimal severity cut-off point were assessed. Results. The IID displayed two distinct dimensions (i.e. painful and emotional) with little item redundancy and good internal consistency (Cronbach's α > 0.83 at each visit). The IID displayed good external validity (Pearson's correlations coefficients >0.60 at each visit) and statistically significant agreement (McNemar's test; P < 0.001 at follow-up) with the reference scale. Results suggest that a cut-off score of ≤24 had adequate precision (>80%) to identify patients with and without moderate MDD. Conclusions. Results suggest that the IID may be a reliable and valid tool for assessing emotional and painful symptoms of MDD.

Key Words::

• Depression
• pain
• psychiatry
• questionnaires
• reliability and validity

Acknowledgements

This study (F1J-MC-B019) was sponsored by Eli Lilly and Company. In compliance with the Uniform Requirements for Manuscripts, established by the International Committee of Medical Journal Editors, the sponsor of this study did not impose any impediment, directly or indirectly, on the publication of the study's results. The authors acknowledge the independent medical writing assistance provided by Cassandra Haley, PhD, and Serina Stretton, PhD, of ProScribe Medical Communications (www.proscribe.com.au), funded from an unrestricted financial grant from Eli Lilly and Company. ProScribe's services complied with international guidelines for Good Publication Practice (GPP2).

Eli Lilly and Company was involved in the study design, data collection, data analysis, and preparation of the manuscript.

All authors participated in the interpretation of study results, and in the drafting, critical revision and approval of the final version of the manuscript. Héctor Dueñas and Joel Raskin were involved in the study design, and data analyses. Richard J Walton was involved in the data analyses. Héctor Dueñas and Carmen Lara assisted with the literature search.

Statement of Interest

Héctor Dueñas is an employee of Eli Lilly de México. Richard J Walton and Renee E Granger are employees of Eli Lilly and Company. Martin Dossenbach and Joel Raskin are employees and shareholders of Eli Lilly and Company. Carmen Lara has no conflicts of interest to disclose.