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Corresponding author: Lynn Doering, RN, DNSc, FAAN, UCLA School of Nursing, 700 Tiverton Ave, Factor 4-266, Los Angeles, CA 90095-6918 (e-mail: ldoering{at}sonnet.ucla.edu).
| Abstract |
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Objectives To evaluate the clinical utility of common self-report and observer-rated instruments for detection of major depression in women after coronary artery bypass graft surgery.
Methods In 66 women being discharged after coronary artery bypass graft surgery, 4 instruments were completed: the Hamilton Depression Rating Scale, Beck Depression Inventory, Beck Depression Inventory Short Form, and Beck Depression Inventory for Primary Care. For each instrument, receiver-operating-characteristic curves were analyzed, and positive and negative predictive values were calculated for cutoff points determined from the curves.
Results At hospital discharge, all 4 instruments yielded highly accurate curves. Compared with cutoffs suggested for patients without medical illness and hospitalized nonsurgical patients, identified cutoffs for screening were higher when all types of depressive symptoms (cognitive, affective, behavioral, somatic) were measured with the Hamilton Depression Rating Scale and the Beck Depression Inventory but lower when only cognitive and/or affective symptoms were measured with the 2 subscales of the Beck Depression Inventory.
Conclusions The Hamilton Depression Rating Scale and both subscales of the Beck Depression Inventory may be useful for detecting major depression in women shortly after coronary artery bypass graft surgery. Further study is warranted to confirm cutoffs in these patients.
In general, rates of depression in women are higher than the rates in men, and outcomes in women tend to be worse.15 Although few reports address depression in women after CABG surgery, rates of depression in women with ischemic heart disease and women with heart failure follow this general pattern. Among patients with heart failure, women are more likely to be depressed than men, and depressed patients tend to be younger than nondepressed patients.16
In the Enhancing Recovery in Coronary Heart Disease trial, female patients reported higher levels of depression and distress than did male patients; the greatest differences occurred among younger women.17 In women undergoing CABG surgery, depression occurs at rates similar to the rates in women with heart failure and the rates in other clinical populations, such as women with diabetes.18,19 Compared with men, women may be particularly susceptible to depression after CABG surgery because women tend to become depressed after a triggering event, such as surgery.20
Despite the prevalence of depression after CABG surgery and its association with mortality and morbidity, clinicians have few practical options for detecting depression, especially in women. Structured diagnostic interviews, such as the Diagnostic Interview and Structured Hamilton (DISH) or the Structured Clinical Interview for the Diagnostic and Statistical Manual, Fourth Edition (DSM-IV), are well validated and reliable but require extensive training and are time-consuming to administer.21,22 Alternatively, self-report and observer instruments have the advantage of being short and easier to use than structured interviews, but most were designed to measure the severity of signs and symptoms of depression only rather than clinical depression.
| Depression increases mortality, cardiac events, and postoperative complications after coronary artery bypass surgery.
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Among self-report instruments, the Beck Depression Inventory (BDI) is considered the reference standard.23 Although it was originally developed for use in psychiatric patients, the BDI has been widely used in both healthy and medically ill populations. Recently, new subscales of the BDI for use with medically ill patients have been developed, including a 13-item version of all cognitive/affective items in the BDI, called the BDI Short Form (BDI-SF),24 and a 7-item version of selected cognitive/affective items, called the BDI for Primary Care (BDI-PC).25 Among observer-rated instruments, the Hamilton Depression Rating Scale (HDRS) is the most widely accepted.26 Like the BDI, the HDRS has been used widely in medically ill populations.
Becks cognitive model of depression offers an appropriate theoretical framework for evaluating these instruments.27 Beck postulates that depressed individuals have a negative bias in their view of themselves, their world, and their future. This negative bias is evident in their cognitive function, in the form of automatic thoughts and negative core schema. Negative cognitive bias triggers negative affective, somatic, and behavioral responses. Thus, evaluation of cognitive, affective, somatic, and behavioral symptoms merit consideration in detecting clinical depression. This theory is consistent with the DSM-IV criteria, the HDRS, and the BDI, all of which include all of these elements; differences exist in the type and number of characteristics assessed in each (Table 1
). By contrast, the BDI-SF and the BDI-PC include only cognitive and/or affective items.
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| Methods |
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Sample and Setting
Women were recruited from 2 tertiary care centers in a major metropolitan area. After the study was approved by institutional review boards, women were invited to participate if they were no more than 75 years old, were having CABG surgery for the first time, and spoke English. A convenience sample of 66 women who completed the predischarge diagnostic evaluation, the observer rating interview, and the BDI as part of the parent study was used.
Procedures
Before each patient was discharged from the hospital, informed consent was obtained, and a research nurse administered the Mini-Mental Status Examination. After confirming a score of 24 or greater on that examination, which is consistent with a lack of cognitive impairment,28,29 a trained interviewer (L.V.D.) administered the DISH before the patient was discharged from the hospital. To confirm the diagnostic results of the interview, all patients classified as depressed were evaluated by a psychiatrist. After both interviews, participants completed the BDI with instructions to consider how they had been feeling for the past 2 weeks. Research assistants who administered the BDI had no knowledge of the results of the diagnostic interview.
Instruments
Diagnostic Interview and Structured Hamilton.
The DISH is a semistructured interview designed to diagnose depression in medically ill patients.21 In validation studies, the DISH and Structured Clinical Interview for DSM-IV resulted in 88% agreement (
=.86).21 Interrater reliability has been established, with 93% agreement between diagnosis by trained interviewers and clinicians and with diagnostic agreement across symptom clusters (
= .75).21,30
Beck Depression Inventory.
The BDI is a 21-item self-reported measure of the intensity of signs and symptoms of depression, with items rated 0 to 3 (0 = no signs or symptoms, 3 = most severe signs and symptoms) and totals ranging from 0 to 63 (Table 1
). Suggested guidelines for cutoff scores are less than 10 for no or minimal depression, 10 to 18 for mild to moderate depression, 19 to 28 for moderate to severe depression, and 29 and higher for severe depression. The BDI is used routinely to monitor changes in signs and symptoms in cognitive behavioral therapy. Concurrent validity of the BDI has been supported by correlations between the BDI and selected concurrent measures of depression and by agreement with clinical psychiatric evaluations of depression.31 Meta-analyses of internal consistency have yielded Cronbach
coefficients of .86 for psychiatric patients and .81 for nonpsychiatric patients.32
Among CABG patients, internal consistency of the BDI is high, with Cronbach
coefficients of .82.33 Widely used to assess the severity of depression in psychiatric patients, the BDI also has been validated in older adults34 and across a variety of medical populations, including patients with diabetes35 or chronic pain36 and patients undergoing hemodialysis.37 The BDI has demonstrated utility for differentiating among medical, nonmedical, and healthy groups32 and is a sensitive indicator of cardiac mortality.38 It has shown discriminative validity in distinguishing higher from lower sympathetic nervous activation in women tested for severity of depressive symptoms.39 In the study reported here, tests of internal consistency yielded a Cronbach
coefficient of .92.
Beck Depression Inventory Short Form.
The BDI-SF includes all 13 cognitive/affective items in the BDI (Table 1
). The BDI-SF was developed in response to concerns that in medically ill populations the use of somatic items to evaluate depressive symptoms might lead to spuriously high scores and overreporting of depression.23 As with the BDI, items are scored from 0 (no signs or symptoms) to 3 (most severe signs and symptoms); total scores range from 0 to 39. The use of only the cognitive/affective items was suggested to assess depression in medically ill patients, with the use of scores of 10 or greater as a cutoff for moderate to severe depressive syndromes.24 With this cutoff, the BDI-SF has demonstrated high sensitivity (100%) and negative predictive value (100%) in patients hospitalized in a general medical ward.24 With a cutoff of 8 or greater, the BDI-SF had adequate sensitivity (79%) and negative predictive value (96%) with diagnostic interviews in a sample of terminally ill cancer patients receiving palliative care and was well correlated (r = 0.96) with the original 21-item scale.40 In the study reported here, tests of internal consistency yielded a Cronbach
coefficient of .89.
Beck Depression Inventory for Primary Care.
Like the BDI-SF, the BDI-PC was designed to minimize the possibility of yielding spuriously high estimates of depression in patients with medical illnesses by focusing on cognitive/affective signs and symptoms. For the BDI-PC, 7 items were selected purposively to correspond to DSM-IV criteria (sadness and anhedonia), to capture important clinical indicators of risk in depressed patients (suicidality), and to reflect those items that loaded most saliently (
.35) on the cognitive dimension of the original instrument (pessimism, past failure, self-dislike, and lack of confidence).41 As with the BDI and BDI-SF, the items are scored from 0 to 3 to reflect intensity of the sign or symptom, but the BDI-PC includes only 7 items. Totals range from 0 to 21. A cutoff of 4 and higher yields strong sensitivity (82%83%) and specificity (82%95%) rates for detection of major depression in medical inpatients and outpatients.25,42 In the study reported here, tests of internal consistency yielded a Cronbach
coefficient of .87.
| Women with heart failure are more depressed than men, and depressed patients are younger than nondepressed patients.
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Hamilton Depression Rating Scale.
The 17-item version of the HDRS is administered via a structured interview in which subjects are asked to respond to questions about the signs and symptoms they had during a specific (2-week) period (Table 1
). Responses are rated by the interviewer, with 8 affective/cognitive items rated on a 5-point scale (0 = no signs or symptoms, 4 = most severe signs and symptoms) and 9 somatic items rated on a 3-point scale (0 = no signs or symptoms, 2 = most severe signs and symptoms). Scores range from 0 to 52. Scores of 24 or higher are generally agreed to indicate severe depression, whereas scores of 18 to 23 represent the moderate range, 7 to 17 signify mild depression, and scores less than 7 indicate no depression.26 The HDRS is sensitive to change over time and treatment and agrees well with overall clinical ratings of severity.43 It has well-documented validity, with a Cronbach
of .81 recently reported44; recent studies also support interrater reliability, with intraclass correlations of 0.96 to 0.97.45,46 For this study, administration time for the HDRS was approximately 30 minutes.
Analysis
Measures of central tendency and dispersion were used to describe the sample. For comparing depressed with nondepressed patients, a t test was used for continuous variables and a
2 test for categorical variables. For each of the instruments and subscales (HDRS, BDI, BDI-SF, and BDI-PC), receiver-operating-characteristic (ROC) curves were analyzed to generate plots of sensitivity versus 1 minus specificity for detecting major depression for every possible cutoff point and to generate graphs of the area under the curve (AUC). The AUC is equivalent to the probability that a randomly selected individual from the positive reference sample has a greater test value than a randomly selected individual from the negative reference sample; an appropriate sample estimate is made by using the nonparametric Mann-Whitney U test.47 Curves are ranked against noninformative curves as less accurate (0.5 < AUC < 0.7), moderately accurate (0.7 < AUC < 0.9), highly accurate (0.9 < AUC < 1.0), and perfect (AUC = 1.0).47
| The Hamilton Depression Rating Scale yielded the fewest false-positives but indicated all true cases.
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Standard formulas were used to calculate positive and negative predictive value for cutoff points determined from each curve. To focus on the utility of instruments for both screening (detecting depressive symptoms) and diagnosis (detecting cases of major depression), we examined each curve for cutoff points that would maximize sensitivity and negative predictive value (for screening) and specificity and positive predictive value (for diagnosis).
| Results |
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The Figure
presents the ROC curve analyses for detection of major depression at hospital discharge. All 4 instruments yielded strong ROC curves, with AUCs exceeding .900 considered highly accurate.47 Cutoff points derived from each curve were examined for sensitivity, specificity, positive predictive value, and negative predictive value (Table 3
). For each instrument, cutoffs from these data differed from those reported in the literature. For the HDRS and BDI, cutoffs for both screening (HDRS
14, BDI
12) and diagnosis (HDRS
19, BDI
24) were higher than those usually reported for symptom onset (HDRS
7, BDI
10). For the cognitive/affective-only instruments (BDI-SF and the BDI-PC), we found lower cutoffs for screening (BDI-SF
4, BDI-PC
2) than previously reported (BDI-SF
8, BDI-PC
4). Similarly, diagnostic cutoffs for these instruments (BDI-SF
12, BDI-PC
5) were lower than those previously reported (BDI-SF
13, BDI-PC
6).
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| Discussion |
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Evaluation of HDRS and BDI
For screening, on the basis of the ROC curves at hospital discharge, we were able to identify cutoffs with high sensitivity (100%) and negative predictive value for each instrument (Table 3
). According to the evaluation of misclassified cases, the HDRS yielded the fewest false-positives and indicated all true cases. A cutoff of 14 or greater (higher than the standard cutoff of 7 or greater) on the HDRS may be reasonable for depression screening in women after CABG surgery. In a recent evaluation48 of the BDI for screening patients with myocardial infarction 1 month after the index infarction, an optimal screening cutoff of 7 or greater was reported when both major and minor depression were considered. The higher cutoff of 12 or greater that we observed for screening with the BDI is probably due to our focus on major depression only.
Evaluation of Cognitive-Only Instruments
According to Becks theory, instruments used to measure all types of signs and symptoms of depression (cognitive, affective, somatic, and behavioral) should be more accurate for detecting major depression than are instruments used to measure only cognitive/affective signs and symptoms. In the evaluation of medically ill patients, both clinicians and researchers have continued to debate the merits of including somatic signs and symptoms as part of clinical depression.4951 For screening of adults hospitalized in medical wards for at least 72 hours, Furlanetto et al24 found that a BDI-SF cutoff of 9 or greater produced the highest sensitivity and negative predictive value.
In our study, the designated cutoff of 4 or greater also allowed detection of all cases of depression. In both studies, the false-positive rates were high, with many nondepressed patients identified as depressed by means of the BDI-SF. For diagnosis, we again observed a somewhat lower cutoff (
12) than that observed in hospitalized medical patients (
14). The discrepancy between the cutoff we identified and those in the earlier report may be due to the different study populations. Compared with general medical patients, surgical patients about to be discharged from the hospital may have had blunting of affective signs and symptoms of depression, as indicated by the low medians and interquartile ranges that we observed. In our surgical population, the median BDI-SF score in nondepressed patients was 2, and 25% of depressed patients scored as low as 6. Thus, compared with the cutoff for patients with medical problems, a relatively low cutoff was required for our surgical patients to ensure high sensitivity for screening and high specificity for diagnosis.
In 2 earlier reports,52,53 the BDI-SF was only moderately accurate in patients hospitalized with diverse medical problems, with an AUC of .85 to .87. Nonetheless, in these reports, the recommended cutoff of 4 or higher produced relatively high sensitivities of 90% to 91%. Again, the optimal cutoffs we observed were lower than those previously recommended. As with the BDI-SF, we suspect that the characteristics of depressive signs and symptoms in patients after CABG surgery must differ in some way from the signs and symptoms of the previously studied medical patients.
When all 4 instruments are considered, patients who have had CABG surgery seem to require a higher threshold for both screening and diagnosis when multimodal instruments (HDRS and BDI) are used, whereas lower thresholds are required when cognitive/affective-only instruments (BDI-SF and BDI-PC) are used. Although further study is needed to confirm these findings, the presence of postoperatively generated somatic signs and symptoms may explain the higher thresholds for the HDRS and the BDI. Conversely, in the case of the BDI-SF and BDI-PC, the omission of somatic signs and symptoms may yield a greater influence of cognitive/affective signs and symptoms, so that a lower level of cognitive/affective signs and symptoms is associated with clinical depression.
Study Limitations
Our study had several limitations. First, we studied only women, so our findings are not generalizable to men or to mixed samples of men and women. Second, our sample size was small. Determination of sample size for ROC analysis depends on interobserver accuracy, accuracy of the curves (AUC), and the ratio of positive and negative cases.54 The adequacy of our sample is supported by our use of a single observer to make all diagnostic determinations (thus eliminating interobserver error), the generation of ROC curves with high accuracy at hospital discharge, and the finding of a prevalence of major depression at hospital discharge similar to the prevalence reported in other studies48 of cardiac patients. Therefore, our sample size should have been sufficient for detecting cases of depression at hospital discharge.
In addition, some differences (eg, a history of clinical depression) between depressed and nondepressed patients might not have been identified because the sample size was small and thus vulnerable to type II error. However, further studies with larger samples that include a greater proportion of depressed women and men would be important to confirm these findings and enhance generalizability across diverse samples of CABG surgery patients. Likewise, further refinement of cutoff points and testing for relevance against different sociodemographic strata in CABG surgery patients would be valuable.
Clinical Significance
Although these pilot data should be used cautiously in drawing inferences for clinical practice, they are clinically significant for testing. For screening, an ideal instrument would have high sensitivity and negative predictive value so that the chance of missing true cases of major depression would be minimized. Thus, all truly depressed patients would be recognized and would receive more in-depth evaluation to confirm the diagnosis. If the purpose of testing is to streamline diagnosis of major depression and enhance recognition of true cases, then high specificity and positive predictive value would be more important.
| Patients who have undergone coronary artery bypass graft surgery require higher thresholds for screening and diagnosis with multimodal instruments than with instruments used to measure only cognitive/affective signs and symptoms.
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For example, the HDRS is an observer-rated instrument that requires the rater to assess patients responses to specific items. Therefore, the HDRS requires more time and training than does the BDI. For settings in which clinicians training and time limit the use of the HDRS, the BDI or its 2 shorter cognitive forms may be reasonable alternatives. These self-report instruments usually take less than 10 minutes to complete, and all yielded somewhat more false-positives than the HDRS, but still indicated all true cases with the screening cutoff given in Table 3
. Of note, cutoff associated with all instruments differed from those standard accepted cutoffs. Further testing in larger samples is warranted to confirm these findings and further evaluate appropriate cutoffs for screening and diagnosis.
| Conclusion |
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| An ideal instrument for screening would have little chance of missing true cases of major depression.
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FINANCIAL DISCLOSURES
This study was supported by grants NIMH K01MH01700 and R01NR009228 from the National Institute of Mental Health.
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