Depression: Making the Diagnosis in Primary Care

By Sally Beattie, MS, RN, CS, GNP

Summary—The prevalence of depression in the general population surpasses that of hypertension, which makes it one of the most frequently treated diseases in the primary care milieu. Unfortunately, up to 50% of cases go undetected, partially because primary care providers lack the time and knowledge to apply established diagnostic criteria to screen and assess for depression.1 Researchers identified two screening questions from the Primary Care Evaluation of Mental Disorders Procedure (PRIME-MD)2 and four core subset symptom criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM) that quickly and effectively pointed to a diagnosis of depression in 1000 subjects.3 Findings were validated with a patient questionnaire that included three depression assessment tools. Results were favorable when compared with the complex DSM IV questionnaire. Also, the core subset of depressive symptoms appeared to differentiate between subjects with milder levels of impairment and those with moderate to severe depression. Clinicians are encouraged to use the two-item PRIME-MD and the SALSA (sleep disturbance, anhedonia, low self-esteem, appetite change) core subset symptom criteria mentioned in this article to facilitate identification of clinical depression in primary care practice.2

Experts estimate 5-9% of adult outpatients seen by primary care providers suffer from a major depressive disorder, and even more report milder but still clinically significant levels of depression. Such high rates of depression in the general population make it one of the most common disorders found in medical practice, with its prevalence surpassing that of hypertension. Studies show that 35-50% of cases go undetected.1,2

The DSM is generally recognized as the ultimate authority for diagnosing psychopathologic conditions; however, it appears few primary care providers use its lengthy, complex criteria to guide diagnosis or treatment.2 Obstacles to recognition of depression by primary care providers include inadequate knowledge of the diagnostic criteria, uncertainty about the most appropriate questions to determine if criteria are met, and inherent time limitations in the primary care setting.4 Researchers wondered if reducing the number of symptoms required to make the diagnosis would make it easier for primary care providers to remember and evaluate them. They set out to answer three questions:

1. What symptoms best predict functional status and well-being?

2. How many symptoms must be present to indicate a diagnosis of depression?

3. How do patients diagnosed by these criteria compare using DSM criteria?

Investigators conducted an analysis to determine if a core subset of symptoms could be used to efficiently and effectively diagnose depression after administering a two-item questionnaire extracted from a recognized screening tool known as PRIME-MD.2

The PRIME-MD was designed for flexible use by busy clinicians to facilitate rapid and accurate diagnosis of common mental disorders seen in primary care. Two of its 26 questions were designed specifically to screen for depression by asking: "In the past month, have you often been bothered by 1) little interest or pleasure in doing things and/or 2) feeling down, depressed, or hopeless?"4 A positive response to either of these triggers an evaluation for major depression.

Identifying a Subset of Depressive Symptoms

One thousand patients seen by 31 primary care physicians in four sites completed the questionnaire. The mean age was 55; 60% were women; 58% were white; and 28% were college graduates. All 1000 completed a validation questionnaire including three assessment tools:

1. Medical Outcomes Study Short Form General Health Survey (SF-20) to measure pain; functioning in physical, role, social, and mental areas; and general health perceptions.5
2. Somatic Symptom Inventory to determine how much a patient was bothered by common symptoms over the past six months.6
3. Zung Depression Scale to measure severity of depression.7

Researchers also assessed disability days and health care utilization by subjects.

Multiple regression analysis was used to identify a core subset of symptoms revealed by the validation questionnaire as most predictive of functional status and well-being. Researchers chose to develop criteria for depression that were maximally predictive of these two outcomes as they represent the primary goals of health care.

Investigators found sleep disturbance, anhedonia, low self-esteem, and change in appetite consistently explained almost all the variance in functional status and well-being attributable to the nine DMS IV symptoms of depression. Researchers found that forcing in the five remaining symptoms did not increase the explained percentage of variance. Of 1000 patients, 325 screened positive for depression. Two of the four symptoms were experienced by 8.3% of study subjects. Another 8.2% experienced three or four symptoms, which gave a depression prevalence rate of 16.5% (165 patients) with a cut-off of just two symptoms. The prevalence rate using DSM-IV criteria was 11.5%. Further analysis indicated that patients who experienced two of the symptoms demonstrated a milder form of depression than those with three or four. This indication was validated by scores obtained from the validation questionnaire tools.2

Comparison with DSM-IV Criteria

From 115 patients with major depression according to the DSM-IV, all but three had at least two of the core subset of depressive symptoms. Based on the validation questionnaire outcomes, these three patients were only moderately impaired. Additional analysis of the 325 patients who screened positive with the PRIME-MD depression screening questions revealed that the identified core subset of depressive symptoms were as effective as the DSM-IV criteria in identifying patients with suicidal thoughts.2

The authors concluded that evaluation of the core subset of four symptoms after screening with the two-item PRIME-MD tool effectively identifies patients needing clinical attention for depression.2 Also, the data indicated the core subset of symptoms identifies and distinguishes between patients with a milder form of depression (2 symptoms) and those with more severe impairment, including suicidal ideation (3-4 symptoms). The analysis indicated the latter group was equally impaired in functional status and well-being as those evaluated using the full set of DSM-IV criteria. A previous analysis comparing six commonly used case-finding instruments with PRIME-MD validated the current findings.8

Authors of the present study presented several caveats regarding interpretation of their results:

• collection of this type of information via clinical interview without PRIME-MD might yield slightly different outcomes;

• recent bereavement, drug and alcohol abuse, and known medical problems were not considered in this data set;

• and although suicidal ideation is not one of the four core depressive symptoms, it must be considered in any patient believed to have a mood disorder.

Implications for Practice

Depression causes tremendous personal suffering, disability, and lost work time at an estimated cost of $43.7 billion in1990 alone.8,9 Patients suffering clinical depression as a primary or a concomitant condition often present with somatic rather than psychological complaints. Studies show the diagnosis is frequently overlooked by time-pressured practitioners. To facilitate diagnosis and lower the percentage of cases missed in the primary care milieu, develop an index of suspicion and include depression in the differential diagnosis when the cause of a patient’s symptoms are unclear or not fully explained by other medical disease processes. Routinely ask the two-item PRIME-MD depression screening questions during the patient assessment. If positive, ask about the core subset criteria for depression that are easily remembered by using the mnemonic SALSA: sleep disturbance, anhedonia, low self-esteem, and appetite change.

A positive diagnosis usually can be made based on an adequate medical interview, observation of the patient, and the help of user-friendly case-finding tools.3,4,9,10 In light of depression’s high prevalence and tremendous disease burden, it is imperative that all providers in the primary care setting become proficient at recognizing and treating depression.

References

1. Depression Guidelines Panel. Depression in Primary Care: Detection and Diagnosis: Clinical Practice Guideline. Washington, DC: U.S. Dept. of Health and Human Services, Public Health Service, Agency for Health Care Policy and Research; 1993. AHCPR 93-0550.

2. Brody DS, Hahn SR, Spitzer RL, et al. Identifying patients with depression in the primary care setting. Arch Intern Med 1998;158:2469-2475.

3. Whooley MA, Avins AL, Miranda J, Browner WS. Case-finding instruments for depression. J Gen Intern Med 1997;12:439-445.

4. Spitzer RL, Williams JB, Kroenke K, et al. Utility of a new procedure for diagnosing mental disorders in primary care, the PRIME-MD study. JAMA 1994;272: 1749-1756.

5. Stewart AL, Hays RD, Ware JE. The MOS Short-Form General Health Survey: reliability and validity in a patient populations. Med Care 1988;26:724-732.

6. Wyshak G, Barsky AJ, Klerman GL. comparison of psychiatric screening tests in a general medical setting using ROC analysis. Med Care 1991;29:775-785.

7. Zung WWK. A self-rating depression scale. Arch Gen Psychiatry 1965;12:63-8. Lichstein PR, Peden JG. Introduction (Proceedings of a symposium, Manage ment of Depression in Primary Care). Am J Med 1996;101(6A):1S-2S.

9. Boswell EB, Stoudemire A. Major depression in the primary care setting. Am J Med 1996;101(6A):3S-9S.

10. Peden JG, Lichstein PR. Management strategies for depression in primary care. Am J Med 1996;101(6A): 18S-25S.