Elsevier

Comprehensive Psychiatry

Volume 49, Issue 2, March–April 2008, Pages 131-140
Comprehensive Psychiatry

A clinically useful depression outcome scale

https://doi.org/10.1016/j.comppsych.2007.10.006Get rights and content

Abstract

If the optimal delivery of mental health treatment ultimately depends on examining outcome, then precise, reliable, valid, informative, and user-friendly measurement is the key to evaluating the quality and efficiency of care in clinical practice. Self-report questionnaires are a cost-effective option because they are inexpensive in terms of professional time needed for administration, and they correlate highly with clinician ratings. In the present report from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project, we describe the reliability and validity of the Clinically Useful Depression Outcome Scale (CUDOS). The CUDOS was designed to be brief (completed in less than 3 minutes), quickly scored (in less than 15 seconds), clinically useful (fully covering the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition symptoms of major depressive disorder and dysthymic disorder), reliable, valid, and sensitive to change. We studied the CUDOS in more than 1400 psychiatric outpatients and found that the scale had high internal consistency and test-retest reliability. The CUDOS was more highly correlated with another self-report measure of depression than with measures of anxiety, substance use problems, eating disorders, and somatization, thereby supporting the convergent and discriminant validity of the scale. The CUDOS was also highly correlated with interviewer ratings of the severity of depression, and CUDOS scores were significantly different in depressed patients with mild, moderate, and severe levels of depression. The CUDOS was a valid measure of symptom change. Finally, the CUDOS was significantly associated with a diagnosis of major depressive disorder. Thus, the results of this large validation study of the CUDOS shows that it is a reliable and valid measure of depression that is feasible to incorporate into routine clinical practice.

Introduction

To determine the impact of treatment it is necessary to evaluate outcome. In mental health clinical practice, this typically is based on unstructured interactions that yield unquantified judgments of progress. This is at variance with other areas of medical care in which outcome is determined, in part, on the change of a numerical value. Body temperature, blood pressure, cholesterol values, blood sugar levels, cardiac ejection fraction, and white blood cell counts are examples of quantifiable variables that are used to evaluate treatment progress. In the mental health field, standardized, quantifiable outcome measures exist for most major psychiatric disorders, yet they are rarely used in routine clinical practice [1].

In the current health care environment, which is concerned with cost containment, treatment efficiency is assuming increasing importance because there is an interest in the relationship between the cost and results of providing services. Cost and outcome are relevant issues to practicing clinicians, clinic administrators, and third party payers, and addressing fiscal concerns can impact on the delivery of appropriate clinical services in routine clinical settings. To determine treatment efficiency in clinical practice, it would require treatment providers to adopt some of the techniques that are standard in research treatment outcome investigations.

If the optimal delivery of mental health treatment ultimately depends on examining outcome, then precise, reliable, valid, informative, and user-friendly measurement is critical to evaluating the quality and efficiency of care in clinical practice. Clinicians are already overburdened with paperwork, and adding to this load by requiring repeated detailed evaluations with such instruments as the Hamilton Rating Scale for Depression (HAMD) [2] is unlikely to meet with success. Self-report questionnaires are a cost-effective option because they are inexpensive in terms of professional time needed for administration and they correlate highly with clinician ratings. To be sure, there are also limitations with self-report questionnaires, such as response-set biases, and their use may be limited by the readability of the scale and literacy of the respondent. However, self-report scales are free of clinician bias and are therefore free from clinician overestimation of patient improvement (which might occur when there is incentive to document treatment success).

Three consumers should be considered in the construction of a self-administered outcome questionnaire to be used in routine clinical practice: the patient, the clinician, and the administrator. Patients should find the measure user-friendly and the directions easy to follow. The questions should be understandable and relevant to the patient's problem. The scale should be brief, taking no more than 2 to 3 minutes to complete, so that upon routine administration at follow-up visits, patients are not inconvenienced by the need to come for their appointment 10 to 15 minutes early in order to complete the measure. This would make it feasible to have the scale completed at each follow-up visit in the same way that blood pressure, cholesterol levels, and weight are routinely assessed in primary care settings for patients being treated for hypertension, hypercholesterolemia, and obesity.

The instrument should provide clinicians with clinically useful information and improve the efficiency of conducting their clinical evaluation; thus, the measure should have practical value to the practicing clinician. Of course, clinicians need to be able to trust the information provided by any instrument they use. Consequently, outcome measures of any kind should have a sound basis in psychometrics, demonstrating good reliability, validity, and sensitivity to change. Clinicians and clinics should also find the instrument user-friendly; it should be easy to administer and score with minimal training.

Clinic administrators likewise want measures to be both reliable and valid. To successfully implement an outcomes assessment program, administrators want measures to have high patient and clinician acceptance. Administrators are also concerned about the cost of an instrument, from the perspective of both the purchase price and the cost of labor to score the scale. Thus, an outcome measure, or outcome assessment program, should be inexpensive to purchase and implement.

Finally, we believe that any instrument constructed for use in clinical settings should meet scientific standards for publication in peer-reviewed journals. It is important that a new measure stand up to critical scientific review and be published in the scientific arena so that other investigators may further examine its properties.

During the past decade, we have established and have been conducting the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project. One of the goals of the MIDAS project is to develop instruments for use in routine clinical practice. Previously, we have described the reliability and validity of a broad-based self-report scale for psychiatric screening [3], [4], [5]; a clinician-rated outcome measure for depression [6]; and single-item self-report indices of depression symptom severity, psychosocial impairment, and quality of life [7]. In the present report from the MIDAS project, we describe the reliability and validity of the Clinically Useful Depression Outcome Scale (CUDOS). The CUDOS was designed to be brief (completed in less than 3 minutes), quickly scored (in less than 15 seconds), clinically useful (fully covering the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition [DSM-IV] symptoms of major depressive disorder [MDD] and dysthymic disorder), reliable, valid, and sensitive to change. Certainly, there is no shortage of self-report depression scales [8]. However, other questionnaires are either too long [9], [10], [11], lack adequate coverage of the DSM-IV diagnostic criteria [12], [13], are expensive to purchase [9], or are somewhat complicated to score [12]. These factors reduce their appeal as outcome tools for use in routine clinical practice. Table 1 lists 15 desirable properties of a depression outcome scale. The CUDOS was designed to possess all 15 characteristics of a depression outcome scale that could be routinely incorporated into clinical practice.

Section snippets

Methods

Individuals presenting for an intake evaluation at the Rhode Island Hospital Department of Psychiatry outpatient practice were asked to complete the CUDOS as part of their initial paperwork. Because we were planning to test the CUDOS' validity by examining its relationship with psychiatric diagnoses, the diagnosticians were kept blind to the subjects' responses on the measure. The Rhode Island Hospital institutional review committee approved the research protocol, and all patients provided

Data analyses

We examined 2 types of reliability of the CUDOS test-retest reliability and internal consistency. We examined convergent and discriminant validity [40] by comparing the correlation between the CUDOS and the Beck Depression Inventory with the correlation between the CUDOS and measures of anxiety, substance use, eating disorders, and somatization. Because depression is frequently comorbid with other Axis I disorders, we predicted that the CUDOS would be significantly correlated with measures of

Internal consistency and test-retest reliability of the CUDOS

The data in Table 2 shows the diagnostic characteristics of the 1475 patients who completed the CUDOS at their initial appointment. The most frequent DSM-IV diagnoses were MDD (42.4%), social phobia (26.0%), generalized anxiety disorder (18.8%), and panic disorder (17.2%).

Internal consistency coefficients were computed separately for the 1475 patients who completed the scale at intake and 100 depressed patients who participated in an acceptance and feasibility study who completed it during a

Discussion

The results of this large validation study of the CUDOS shows that it is a reliable and valid measure of depression. A previous study demonstrated that the scale is feasible to incorporate into routine clinical practice [15]. On average, the scale takes less than 2 minutes to complete, and more than 95% of patients were able to complete it in less than 3 minutes [15]. Patients did not find scale completion burdensome and were willing to complete it on a regular basis [15]. The CUDOS achieved

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