The purpose of this investigation was to determine the utility of the CES-D screening instrument for depression among persons with SLE. In this sample, 17% of persons met criteria for major depressive disorder and 26% met criteria for any mood disorder, including major depressive disorder, minor depression, and dysthymia, using a comprehensive structured clinical interview from the DSM-IV. To our knowledge, the present study is one of few studies employing structured clinical interview techniques for depression. Notably, prevalence rates from our study were similar to a previous study using comparable (DSM-IV based) interview techniques (19
). In this comparable study of women with SLE, Nery and colleagues found mood disorders present in 27% and a diagnosis of major depressive disorder in 22% (19
). Results of the threshold estimation techniques suggested a cut point score of 24 and above on the CES-D, which correctly classified 92% of participants as current major depressive disorder present versus absent. Overall, the CES-D appears to be a useful screening measure to identify patients who have a range of disease activity levels to detect the presence of major depression.
This proposed cut score of 24 is very similar to the commonly used cut score of ≥23 for “probable depression” (10
) and may have some improved psychometric properties, but was not statistically different. Our results suggest that in this disease population, a higher cut score may be advantageous in identifying patients who likely meet criteria for major depression. This cut score of 24 is also similar to a recently suggested cut score of 25 for older adults (20
We also investigated the utility of the CES-D for detection of any mood disorder, including major depression, minor depression, and dysthymia. To detect any of these 3 mood disorders, the threshold estimation techniques suggested a cut point score of 20 and above, which was observed to yield optimal diagnostic accuracy. Although our classification of any mood disorder is heterogeneous and represents a broad category of mood disorders, sensitivity and specificity remained reasonably high at 87% for both. These results suggest that the CES-D may also be useful for the detection of this broad category of mood disorders, including subsyndromal depression. Using the CES-D to detect patients at risk for a range of mood disorders may be a useful approach, particularly to identify those with subsyndromal depression. Subsyndromal depressive symptoms not meeting criteria for a depressive disorder have been observed to place patients at risk for poor outcomes (21
). Therefore, monitoring those patients who endorse these symptoms of depression more closely in the course of clinical care may be warranted.
It is well understood that assessing depression in a medical population presents specific measurement challenges. One of the most prominent of these challenges is the issue of symptom contamination. Clearly somatic symptoms of depression overlap with disease-related symptoms, particularly decreased energy, concentration difficulties, sleep, and appetite disturbance. Empirical methods have been previously employed to address this problem by removing contaminating items (22
), or in selecting measures that are relatively somatic symptom free (e.g., the Geriatric Depression Scale). In our study, we compared our empirically derived cut scores to a comparably derived cut score on the modified somatic symptom–free measure previously suggested for use in rheumatoid arthritis. These results suggest that by removing the somatic symptoms, we may not be improving detection of depressive disorder in this condition, and in some instances the cut score derived from the original CES-D performed better than a modified version. Overall, we believe that the unmodified CES-D may be useful and has the advantage of maintaining the psychometric integrity of the measure. Maintaining the original item structure facilitates broad use of the CES-D in SLE and enables comparisons across populations. Furthermore, while there is certainly the potential of overlapping symptoms causing inflation of depression severity scores and thereby shifting base rates of depression in populations, this potential relies on the assumption that these somatic symptoms of depression are invariably etiologically linked to the medical condition. It is equally possible that these somatic symptoms of depression are etiologically linked to an underlying depressive disorder (23
), and removing these symptoms may underestimate the prevalence and severity of depression. Recently, Thombs et al observed that somatic symptoms were not endorsed at substantively higher rates by scleroderma patients compared to matched community controls, further supporting this idea (24
). In this study, we cannot ascribe the etiology of our somatic symptoms. However, it is important both in the clinical and research setting to remain cognizant of these issues, and future longitudinal studies tracking the evolution of these symptoms in SLE are warranted.
Limitations of this study include the potential for reduced generalizability. First, healthier individuals may be more likely to participate in this study, particularly since it required travel to our CRC. However, the prevalence of significant disease manifestations in this cohort suggests that disease severity may be representative of persons with SLE. Second, we included only English-speaking patients, limiting the generalization of our results to non-English–speaking patients with SLE. Third, with the exception of SLE diagnostic status, health characteristics are collected by self-report. It is possible that our patients are unaware of their health status across all factors. Fourth, the sample sizes of participants who met criteria for depression are relatively small, and further psychometric confirmation is warranted in a larger sample. Fifth, although the CES-D is easily administered and scored, it is also somewhat longer (i.e., 20 items) than other depression scales (e.g., the Patient Health Questionnaire 9 [PHQ-9] [25
]). There is increasing reliance on these briefer measures, yet psychometric evaluation of these briefer measures needs to be completed in complex conditions such as SLE. For example, although the PHQ-9 has been shown to be associated with the CES-D in rheumatic disease (26
), the PHQ-9 was not validated against a structured clinical interview for mood disorders. In addition, we compared the CES-D to a single-item measure that may lack sensitivity compared to other established ultra-short measures previously studied (27
). Furthermore, there is the potential for spectrum bias in that we included patients who were potentially being treated for depression in this sample, and therefore there may be some increase in our estimates of diagnostic accuracy. Finally, although the screening and the gold standard depression measures were both evaluated at the same visit, disease characteristics, quality of life, and the single-item question were evaluated by the preceding LOS telephone interview, and it is possible that symptoms and some aspects of disease activity may have changed between the telephone interview and their CRC visit.
Depression is a common and debilitating comorbidity associated with SLE. Results from this study suggest that the CES-D, which is quickly administered and easily scored, may be a useful tool in the research and clinical setting to identify depression among persons with SLE. In the clinic, it is important to highlight that screening for depression is only one aspect of appropriate care in both primary care and subspecialty clinics. One potential disadvantage for depression screening is the possibility of opportunity cost, in that even a relatively brief screen for depression could detract from screening and assessment of other clinical issues. Second, merely screening for depression may not be beneficial in the absence of a comprehensive care model with adequate resources for not only assessment, but also treatment and followup (28
). Randomized clinical trials are necessary in SLE and other rheumatic diseases to fully understand the benefit–harm tradeoffs for screening for depression in the context of specialty care.
In sum, depression in the context of SLE, like many chronic conditions, is a substantial risk factor for a number of poor health outcomes, including decreased treatment adherence and increased disability (28
). Additionally, mental health status is among the strongest predictors of health care costs among patients with SLE (30
). A number of effective treatments for depression are available and identifying patients at risk for significant depressive disorders in the context of a comprehensive care model could substantially improve the quality of life for patients with SLE.