Screening for Depression in Adults (continued)
Wells and colleagues combined screening and a quality improvement program for depression treatment in 46 primary care clinics and measured the effect on treatment and outcomes of depression.24 Patients were enrolled if they screened as positive on a two-question instrument. Patients received the Composite International Diagnostic Interview criterion standard examination, but participation was not based on its result. The investigators enrolled 1,356 patients and followed them for 12 months. Randomization was at the level of the practice, and the intervention included feedback of the results of the screening test and a request that the provider schedule a visit within two weeks. Intervention practices also received educational materials, assistance in treatment initiation and maintenance, and access to nurse-led medication followup or to cognitive-behavioral therapy.
At 12 months, the proportion of patients receiving appropriate treatment (defined as any appropriate antidepressant or at least one visit to a mental health provider) was higher in the intervention group than in the control group (59 percent vs. 50 percent; difference, 9 percent; CI not reported; P = 0.006). On the basis of Center for Epidemiologic Study Depression score, intervention-group patients were less likely than controls to be depressed at six months (55 percent vs. 64 percent; difference, -9 percent; CI, -15 percent to -3 percent).
Katzelnick and associates compared the benefits of a systematic primary care-based depression treatment program for depressed "high utilizers" not already receiving treatment of depression.12 Using a health maintenance organization database, they defined eligible patients as those who had had ambulatory visits at a rate greater than the 85th percentile over two years. They then identified depressed patients by using a two-stage telephone screening process. Initial screening was performed by using the depression-specific portion of the Structured Clinical Interview for DSM-IV; patients who screened positive then completed the Hamilton Depression Scale and were eligible if their score was greater than 15.28 The investigators randomly assigned practices to the intervention program or to usual care. Patients receiving usual care were notified that they had screened positive for depression and were counseled to see their physicians, but no feedback was given directly to providers. Intervention-group patients were invited to participate in a depression management program that consisted of patient education materials, physician education programs, telephone-based treatment coordination, and antidepressant medication treatment that was initiated and managed by the primary care physician. In an intention-to-treat analysis, patients who received the depression management program were significantly more likely than usual care recipients to fill a prescription for antidepressants in the first six months (82 percent vs. 32 percent; difference, 50 percent; CI, 41 percent to 58 percent). At one year of followup, 55 percent of depression management program participants and 72 percent of usual care recipients (difference, -18 percent; CI, -27 percent to -8 percent) were still depressed.
Rost and coworkers examined the effectiveness of a systematic approach to identification and treatment of depression within primary care practices.13 The researchers randomly assigned 12 practices to usual care or a quality improvement intervention. They identified patients by using initial screening questions about anhedonia or depressed mood, followed by confirmatory diagnostic questions from the Inventory to Diagnose Depression. Usual-care recipients received no further treatment, whereas intervention recipients received materials designed to increase adherence to medical therapy and intervention staff were offered additional training. The intervention improved outcomes in patients who had not recently been treated for depression but not in patients who had been recently treated for depression (mean change in Center for Epidemiologic Study Depression score, -8.2 [P < 0.05] vs. -3.5 [P > 0.05], respectively).
Feedback of screening results to providers generally increases the recognition of depression, especially major depression, by a factor of two to three. The absolute increases in the diagnosis of depression range from 10 percent to 47 percent. In contrast, trials examining the effect of screening and feedback on treatment rates have had mixed results. In three studies, the documented rates of treatment were nearly equal in the intervention and control groups.11,16,20 Other studies, however, found improvements in the rate of treatment; increases in the prescription of antidepressant medication were more common than changes in mental health referrals.
The results of individual studies were also mixed with respect to the effect of screening on clinical outcomes: Some found positive results, whereas others did not (Table 5). The wide variation in interventions tested, outcome measures used, and timing of followup assessments all hamper interpretation of overall results. Seven of 10 studies reported the proportion of patients who were still depressed at some time after initial screening. In these studies, the proportion of patients who were still depressed was lower in the intervention group than the control group, although results were significant in only three studies. Of the three studies that examined health outcomes but did not report the proportion of depressed patients, two had positive results for some outcomes13,14 and one reported no effect for any outcome.23
We examined several potential factors to explain the mixed results. We found no consistent relationships between differences in outcomes and patient and provider characteristics, use of particular outcome measures, varying duration of followup, or trial quality.
The trials that we identified examined a range of strategies, including simple feedback of scores obtained from depression screening questionnaires; feedback given in the context of general education efforts for providers; feedback with treatment advice that may or may not have been tailored to specific patients; and integrated recognition and management approaches that relied on multiple system supports within the clinic to assure prompt, coordinated followup of diagnosis and treatment. Data from existing trials do not definitively rule in or rule out clinical benefits from less intensive interventions, such as feedback alone. Limited data suggest that delayed feedback of results, as provided by Dowrick, may be less effective than immediate feedback.20 Intensive, integrated identification and management that incorporated quality improvements in clinic systems have demonstrated clinical effectiveness in broad-based primary care clinic populations.12,24
Many trials that did not find a statistically significant difference in outcomes were not sufficiently powered to exclude clinically important differences in outcomes. For example, the point estimates of effect in the studies by Williams11 and Whooley25 and their colleagues, both of which were considered "negative" trials, were similar to the effect seen in the larger trial by Wells and associates,24 which had a statistically significant result and has been interpreted as a "positive" study. This finding suggests that the mixed results may be explained in part by differences in adequacy of sample sizes among trials.
Because many trials had insufficient power to exclude the possibility of clinically significant changes in clinical outcomes, we used meta-analysis to determine a summary estimate of effect.
We used a random-effects model to combine the seven trials that had sufficient data for meta-analysis (Figure 1). The summary relative risk for remaining depressed was 0.87 (CI, 0.79 to 0.95) for intervention recipients, suggesting that screening provided a 13 percent reduction in relative risk. The summary estimate of the risk difference was -9 percent (CI, -14 percent to -4 percent). We detected heterogeneity in the results for the outcome of reduction in relative risk (P= 0.052), in large part because of the strongly positive study by Katzelnick and associates.12
Because of the heterogeneity in the full meta-analysis, we performed an alternative analysis from which we excluded the latter trial (Figure 2). In this alternative analysis, the summary risk reductions with screening were slightly smaller (relative risk, 0.90 [CI, 0.82 to 0.98]; summary risk difference, -7 percent [CI, -11 percent to -3 percent]) but heterogeneity was reduced (P= 0.16).
Whether care that incorporates screening for depression is superior to care based on usual methods of case identification is controversial. Multiple studies have examined the effect of providing feedback on results of screening for depression to providers in primary care settings. The rate of detection and diagnosis of depression, which are based mainly on chart review or completion of a study-specific form, increased by 10 percent to 47 percent in most studies reporting this outcome. The effect on the proportion of patients receiving treatment was mixed: Some studies showed large increases,18,19,24 whereas others found no significant effect.11,16,20,25
Some individual trials examining the effect of screening on clinical outcomes have found positive results, but others have not. Many studies have been underpowered to detect clinically important differences in effectiveness. When the results of trials reporting interpretable clinical outcomes are combined, summary estimates suggest that screening is associated with a 13 percent reduction in relative risk and a 9-percentage point absolute reduction in the proportion of patients with persistent depression. Heterogeneity in trial results was noted on statistical testing, in large part because of the large positive effect reported in a trial that involved depressed patients who had frequent clinic visits.12
However, an alternative analysis that excluded this trial, and hence had less heterogeneity, showed only slightly smaller benefit from screening. These findings suggest that screening is probably effective in primary care patients with depression who are not high utilizers.
If screening can increase the proportion of patients achieving remission by 9 percent at 6 months, approximately 11 patients with depression would need to be identified to produce one additional remission. If the prevalence of treatment-responsive depression in primary care patients is 10 percent, 110 patients would need to be screened to produce one additional remission after six months of treatment.
Other reviewers have also examined the value of screening for depression and have reached divergent conclusions. Gilbody and coworkers performed a systematic review of routinely administered questionnaires for anxiety and depression published through 2000.29 They identified six studies, five of which were included in our review. They did not include the recent trials by Callahan,19 Williams,11 and Whooley25 and their colleagues, nor did they include the newer trials that used integrated efforts to improve recognition and treatment systems.12,13,24 They concluded that routine questionnaires did not increase recognition, treatment, or outcomes of depression, but their failure to include several large, recent studies with positive outcomes limits the validity of their conclusions.30
Kroenke and associates performed a systematic review of studies published through May 1998 that addressed diverse interventions to improve recognition and treatment of mental disorders (primarily depression and anxiety) in primary care.31 They identified 27 randomized trials of interventions; of the 11 trials that focused on depression, we included seven in our review. Most interventions, including screening and feedback, improved recognition and treatment; about half of the studies showed improved outcomes. The researchers chose not to combine the results in a meta-analysis because the studies used different outcome measures.
Several recent cost-effectiveness analyses have addressed the question of whether a modest improvement in depression outcomes warrants the increased effort of screening and providing systematic support for treatment. Valenstein and coworkers developed a cost-utility model to examine the consequences of screening a hypothetical cohort of 40-year-old adults, using estimates derived from the literature.32 In the base case of their Markov model, they assumed a prevalence of major depression of 8 percent; a sensitivity and specificity for the detection of major depression of 84 percent and 85 percent, respectively; and a cost of screening of $5.00 per person. They also assumed that 35 percent of patients would have full remission without treatment and that rates of full remission in standard or enhanced care settings would be 45 percent and 50 percent, respectively. They estimated that one-time screening had a cost-utility ratio of about $45,000 per quality-adjusted life-year gained; annual screening had a cost of more than $100,000 per quality-adjusted life-year gained.
Using data on costs and effectiveness obtained directly from trial by Wells and colleagues,24 Schoenbaum and coworkers33 examined the cost-utility of the screening and treatment support program studied by Wells and colleagues. Relative to usual care, the enhanced program, which included one-time screening and support to improve treatment, yielded additional benefits at a cost of $10,000 to $35,000 per quality-adjusted life-year gained. In a similar analysis that used data obtained directly from the study by Katzelnick and associates,12 Simon and colleagues34 found a cost per depression-free day gained of $51.84 (CI, $17.37 to $108.47).
Cost-effectiveness data from the two recent trials of systematic efforts to screen for depression and provide integrated support for treatment suggest that such programs can be implemented efficiently and can produce cost-effectiveness ratios similar to those of other commonly performed preventive services, such as screening for mammography in women older than 50 years of age or treatment of mild to moderate hypertension. Further research is required to determine which components of these integrated programs are most effective and to determine whether more efficient means of delivering effective care are possible.
This study was developed by the Research Triangle Institute-University of North Carolina Evidence-based Practice Center under contract to AHRQ (contract No. 290-97-0011), Rockville, MD.
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Source: U.S. Preventive Services Task Force. Screening for Depression in Adults: Summary of the Evidence. Ann Intern Med 2002;136(10):765-76.
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