An Item Response analysis of the Hamilton Depression Rating Scale using shared data from two pharmaceutical companies.

Although the Hamilton Depression Rating Scale (HAMD) remains the most widely used outcome measure in clinical trials of Major Depressive Disorder, the psychometric properties of the individual HAMD items have not been extensively studied. In the present paper, data from four separate clinical trials conducted independently by two pharmaceutical companies were analyzed to determine the relationship between scores on the individual HAMD items and overall depressive severity in an outpatient population. Option characteristic curves (the probability of scoring a particular option in relation to overall HAMD scores) were generated in order to illustrate the relationship between scoring patterns for each item and the range of total HAMD scores. Results showed that Items 1 (Depressed Mood) and 7 (Work and Activities), and to a lesser degree, Items 2 (Guilt), 10 (Anxiety/Psychic), 11 (Anxiety/Somatic), and 13 (Somatic/General) demonstrated a good relationship between item responses and overall depressive severity. However, other items (e.g. Insight, Hypochondriasis) appeared to be more problematic with regard to their ability to discriminate over the full range of depression severity. The present results illustrate that co-operative data sharing between pharmaceutical companies can be a useful tool for improving clinical methods.