The main findings of this systematic review are that: (1) there are few examples of screening tools with high sensitivity and specificity using an a priori-defined cutoff score in more than one CHD sample. When results from studies that used a pre-specified score were available in more than one sample, estimates of diagnostic accuracy were inconsistent. When exploratory data analysis methods were used to both generate a cutoff score and assess the accuracy of that cutoff score in the same sample, different studies tended to produce cutoffs that were inconsistent across studies; (2) depression treatment improves symptoms of depression in post-MI and stable CHD patients, although symptom reductions are modest; (3) antidepressant treatment has not reduced depressive symptoms compared to placebo in two trials with HF patients, although one small trial was stopped prematurely, and the other trial provided nurse-facilitated depression management services to patients in both the antidepressant and placebo groups; and (4) no RCTs have evaluated whether routine depression screening in CHD would improve depression outcomes.
The AHA has recommended that all CHD patients be routinely screened for depression 
, but the present systematic review did not find any evidence that depression screening would improve outcomes. This finding is not unique to CHD, since there are no published trials in any patient group where patients screened for depression had better depression outcomes than patients not screened 
. On the other hand, a 2008 meta-analysis 
reviewed 11 trials of depression screening in primary care and found several trials where screening increased identification or treatment of depression, but none where screening improved depression outcomes, even though primary care settings are generally much better equipped to manage mental health problems than cardiology settings.
In cardiovascular care settings, several observational studies have reported on the administration of depression questionnaires. One study 
examined the 2-step protocol recommended by the AHA 
, in which the 2-item PHQ-2 was administered to 3,504 of 4,873 admitted patients, and patients with a positive PHQ-2 screen were administered the PHQ-9. Using this approach, 140 patients were identified as possibly depressed. The study authors concluded that depression screening is feasible, but did not describe the referral and follow-up process, estimate costs, or assess whether benefit was obtained. Other observational studies have reported that implementing screening did not increase recognition of depression compared to settings without screening 
; that no new, previously unrecognized cases of depression were identified through screening 
; and that patients with positive depression screens only received follow-up assessments if there was a psychiatrist physically present in the cardiology clinic at the time of the screening, but not if an outpatient psychiatry referral was made 
In primary care, the UK's Quality and Outcomes Framework pay-for-performance program introduced routine depression screening for patients with CHD or diabetes in April 2006 
. In this context, a retrospective cohort study 
examined records from April 2007 through March 2008 of 94,570 CHD or diabetes patients from 237 general practices in Scotland, including 1,245 physicians. Of all patients with CHD or diabetes, 67,358 were screened for depression (71%), and 2,269 of those screened (3%) received a new diagnosis of depression or initiated treatment. The number needed to screen was 976 for a new diagnosis of depression and 687 for initiation of antidepressant treatment. Data were not available to determine screening resulted in improved depression outcomes.
The AHA website lists more than 20 patient care guidelines issued since the 2008 AHA Advisory on depression screening 
. None has recommended that routine screening be implemented as recommended in the Advisory. One guideline statement on secondary prevention 
cited a 2009 editorial that urged the AHA to reconsider its depression screening recommendation 
and suggested that depression screening in CHD might be considered, but only if patients have access to case management services in collaboration with their primary care physician and a mental health specialist. This recommendation differs from the AHA Science Advisory, which recommended routine screening followed by referral of all positive screening results for evaluation by a professional qualified in the diagnosis and management of depression. It is closer to the U.S. Preventive Services Task Force depression screening recommendation for primary care 
, which specifies that screening should only occur when integrated depression care systems for evaluation and case management are available. No trials, however, have assessed whether screening in CHD with referral to primary care would benefit patients, and no trials have shown that screening in the context of integrated depression care systems would benefit patients even in primary care 
. This was an important reason why the UK National Institute of Clinical Excellence 
did not recommend routine depression screening in primary care. Consistent with this, the authors of the Scottish primary care study 
concluded that the impact of depression screening, even in terms of case identification and new treatment, were small and that health care systems should carefully consider the resource implications of these programs.
Depression screening can benefit patients only to the extent that it identifies depressed patients not already diagnosed or treated for depression, successfully enrolls those patients in treatment, and achieves positive treatment results. As described recently 
, antidepressant treatment rates are already high and trending upward in CHD patients 
. By 2002, for instance, 16% of post-MI patients aged 65 and older in Ontario, Canada were prescribed antidepressant medication 
. Furthermore, existing studies appear to exaggerate the accuracy of depression screening tools due to the inclusion of already diagnosed and treated patients, who would not be screened in clinical practice 
, as well as due to the selective reporting of well-performing results from cutoff scores that generate high levels of accuracy, even though this results in substantially different cutoffs being reported across studies 
. Finally, treatment of depression is more effective in patients with high levels of symptoms, and most of those who are newly detected via screening would be expected to have less severe symptoms of depression 
Without evidence that depression screening benefits CHD patients, the potentially considerable resources and costs that would be involved in implementing routine screening must be even more carefully considered 
. Practically speaking, costs would include not only administering screening tests to all CHD patients, but also following up on positive depression screens that would be expected in perhaps one-third of all CHD patients 
, even though most would turn out not to be depressed. The optimal interval and associated costs of rescreening must also be considered as ongoing screening would be expected to divert scarce resources away from an overburdened mental health system that already struggles to provide adequate mental health care 
Depression screening would almost certainly increase the number of patients using antidepressants, and potential harms of even more widespread use of antidepressants by CHD patients must therefore be considered. Selective serotonin reuptake inhibitors (SSRIs) may act as antiplatelet agents, which can increase the risk of major bleeding, especially when used along with the combination of aspirin and a thienopyridine antiplatelet drug like clopidogrel 
or in patients taking warfarin 
. In addition to this risk, many antidepressant drugs inhibit cytochrome P450 isoenzymes and can result in important drug-drug interactions with cardiac medications 
. For example, an interaction in patients with acute MI between the SSRI paroxetine and the commonly-prescribed beta blocker metoprolol has been described 
. In addition to the well-recognized cardiac risks of the tricyclic antidepressants 
, the serotonin-norepinephrine reuptake inhibitor antidepressants may increase blood pressure and heart rate 
, and several antidepressant classes may have unfavorable effects on heart rate variability 
. Reports of potential adverse cardiovascular effects of antidepressant drugs 
suggest that additional studies that evaluate cardiovascular side effects of antidepressant drugs in greater numbers of patients followed for longer time periods may be warranted.
The AHA recommendation for depression screening in CHD 
was made without any evidence that this would improve depression outcomes. The present systematic review shows that, nearly 4 years since the AHA recommendation on depression screening, there is still no evidence that demonstrates that this potentially very costly strategy would benefit patients. There are prior examples where the AHA has recognized the lack of evidence supporting recommendations and, commendably, revised those recommendations 
. We hope that the AHA will similarly reconsider its recommendation for depression screening of all CHD patients.