The consistency of the Hamilton Depression Scale (HDS) as a measure of the severity of depressive states has been examined when the scale was used weekly during a trial when imipramine. By use of logistic models (Rasch) the consistency of the HDS has been considered across patient-variables as age, sex, plasma levels of imipramine, and diagnosis. The results showed that the original 17-item HDS was without adequate consistency, i.e. the total score of the sample of items was no one-dimensional measure of depressive states. However, a melancholia subscale of the HDS contained items the total of which can be used to compare patients quantitatively, although in some part of the analysis one of these items showed ceiling effect. It was concluded that the melancholia subscale (containing the items depressed mood, guilt, work and interests, retardation, psychic anxiety, and general somatic symptoms) can form the basis for further improvements in the field of quantitative rating scales for depressive states.
A total of 97 patients, who participated in two studies on the relationship between the clinical effect and plasma levels of imipramine and clomipramine, were examined for improvement curves by use of weekly ratings on the Hamilton Depression Scale (HDS). Although we confirmed that our six-item HDS subscale, in contrast to the total 17-item HDS, was a one-dimensional measure of depression, the Rasch analysis showed that the weekly improvement in subscale scores only applied to the individual patient, i.e. an average improvement curve for a group of depressed patients is an abstraction to which the individual curves cannot be transferred. Our results indicate, however, that when the subscale scores are transformed into three clinical categories of depression: no, mild (minor), moderate/-severe (major) they could be described by a common improvement curve for all patients. This is illustrated by the percentage of patients who, week to week, changed from major to minor or no depression, or from minor to no depression. We found no specific improvement pattern for imipramine or clomipramine which could be used diagnostically. There is reason to assume that patients completing a controlled trial necessarily will follow a monotonic improvement curve, and the improvement pattern of all patients fulfilling the entry criteria should, therefore, always be reported. The present study thus indicates that calculation of average improvement curves is neither clinically nor statistically meaningful, and should be replaced by measures of changes in number of patients in different main severity categories, or by the final rating score. No difference in outcome between imipramine and clomipramine was shown neither on the subscale nor on the 17-item HDS.
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