We found that a simple 2-item instrument was an effective tool for identifying major depression in patients who had CHD and had similar test characteristics to 3 other more time-consuming screening instruments for depression. A “no” response to the 2 items made depression highly unlikely, with a negative likelihood ratio of 0.14 and a posterior probability of 4%. Our results suggest that a simple 2-item instrument can be used to screen for depression in a diverse population of patients who have CHD. A negative test result effectively rules out depression so that no further screening is necessary.
Sensitivity should be maximized when choosing a screening instrument for depression so that cases are not missed. We found that the 2-item instrument was 90% sensitive for identifying major depression. However, its low specificity and low positive predictive value mean that less than half of patients who have a positive result on the 2-item screen will ultimately meet criteria for major depression. Thus, any patient who has a positive result on the depression screen should have a follow-up diagnostic interview to confirm the diagnosis of depression.18
A diagnostic interview for depression can be performed quickly and safely by a cardiologist. Major depression is defined by depressed mood or loss of interest in nearly all activities for ≥2 weeks (the 2 symptoms asked in the 2-item instrument), accompanied by ≥3 or 4 of the following symptoms (for a total of 5 symptoms all together): insomnia or hypersomnia, feelings of worthlessness or excessive guilt, fatigue or loss of energy, decreased ability to think or concentrate, change in appetite or weight, psychomotor agitation or retardation, and recurrent thoughts of death or suicide.18
If practitioners find that the 2-step process of administering the 2-item screen followed by a diagnostic interview is not feasible, an alternative approach is to administer the PHQ-9 alone. A cutpoint ≥10 on the PHQ-9 is only 54% sensitive, but its 90% specificity and high positive predictive value mean that patients who screen positive need not undergo a follow-up diagnostic interview to confirm the diagnosis of depression. The PHQ-9 is a simple self-report instrument that can be completed in <2 minutes while the patient is in the waiting room or having vital signs measured. Because the PHQ-9 misses 46% of cases, we prefer to use the 2-item instrument and to confirm any positive screening result with a diagnostic interview for depression. However, because of the high prevalence of unrecognized depression in patients who have CHD,1,2
administering the PHQ-9 allows for identification of >50% of depression cases without the need for further confirmation.
It has been estimated that up to 30% of patients who have stable heart disease also have depression,1,2
and in our sample, 22% of subjects had major depression by the diagnostic interview. Depression is increasingly recognized as a strong predictor of morbidity and mortality in patients who have CHD.4
Studies have demonstrated that, although primary providers can provide effective therapy (without referral) for up to 75% of patients who have depression, most cases of depression are unrecognized or inappropriately treated.19,20
Therapies for depression are safe and effective in patients who have coronary disease. Selective serotonin reuptake inhibitors have been proved safe in patients who have CHD and may even have cardioprotective effects.21,22
In addition, when referral is necessary, psychosocial interventions can improve psychological functioning23
and decrease cardiovascular morbidity and mortality in patients who have CHD.24,25