Depression in primary care: Tools for screening, diagnosis, and measuring response to treatment

Use of validated scales in screening, diagnosis, and measuring response to therapy in depression is an essential part of providing appropriate care. Practitioners who become familiar with their use can improve diagnostic accuracy, save time, provide more consistent patient care, and monitor a patient’s complex emotional and behavioral responses to therapy. This article reviews the choice, uses, and clinical relevance of some commonly used tools, and makes recommendations for their routine incorporation into family practice.

Introduction

How many times have physicians wished they could measure a serum sadness level, and show the report to their skeptical patients, thus convincing them that they have a medically treatable disorder? After all, this is the model we use for diabetes, thyroid disease, elevated cholesterol, and many other chronic illnesses. Even when we reach that moment where there is widespread public acceptance that clinical depression, despite its multifactorial causes, is a treatable illness, we will need to use diagnostic tools to confirm our clinical suspicions, inform our patients, and monitor their treatment outcomes.

Symptom-based psychiatric rating scales were developed more than 40 years ago to assign numerical values to a complex range of patient behaviors, affects, and feelings. They have since proliferated into a bewildering array of tools designed for a variety of purposes, some very general in their scope, and some quite narrowly focused. This article is not intended to be a comprehensive review; rather it is an attempt to identify and describe a few such tools that can be easily incorporated into a busy clinician’s repertoire to improve diagnosis and management of depression.

Why use symptom-based rating scales?

Although we routinely rely on clinical data, most explanations of how to interpret diagnostic data are confined to laboratory and X-ray reports. Yet symptoms and signs usually produce far more powerful support of diagnostic hypotheses than we can ever derive from the laboratory. Rating scales are not intended to provide a substitute for good clinical judgment. Once we have a clinical suspicion that depression plays a role in a particular patient’s problems, we want reliable, accurate ways of confirming the diagnosis and monitoring the patient’s progress over time. We need psychometrically sound, user-friendly tools that give us clinically useful information, and that are reliable, valid, and consistent for a variety of patients and settings when administered by different clinicians.

To choose the correct tools we need to determine the goals of our assessment. Screening tools, which give us a quick indication of whether further assessment is warranted, need to have high sensitivity (few false-negatives). Diagnostic tools need good content validity (do they measure what we think they do?), test-retest reliability (reliability over time), good inter-rater reliability (agreement between clinicians), and high specificity (fewer false-positives). When we use scales to evaluate treatment outcomes we need good test-retest reliability and the scale needs to be sensitive enough to detect clinically significant changes in a variety of domains. The gold standard for comparison of all these tools is always a focused, in-depth interview by an experienced mental health clinician. For busy physicians, an ideal test would be short, straightforward, and reliable for screening, diagnosis, and outcome assessment.

Which tools to use?

In most clinical settings we are likely to have multiple goals of assessment and a minimum of time, so careful choice of tools is crucial. Any assessment must be individualized to acknowledge language/cultural differences, intellectual or cognitive impairments, age-specific issues (children, teens, the elderly), co-morbid psychiatric or other illness (anxiety, bipolar disorder), or concurrent substance abuse (e.g., the CAGE questionnaire is useful). Risk of suicide must always be evaluated.

Both self-report inventories and clinician-rated scales are available.[1] Some are in the public domain, while others are protected by copyright and require payment of a fee for their use. Ultimately, a clinically useful diagnostic test must do three things: provide an accurate diagnosis, support application of an efficacious therapy, and ideally, lead to a better outcome for the patient.

The complete evaluation process is impractical for an individual physician to apply to each test he or she uses, so this article will summarize some of the most useful validated tools in depression. As a busy doctor you can choose and become familiar with these few, thereby improving the quality of your patient assessments. Most of the frequently used instruments show robust correlations among themselves, although the self-rating scales show better correlation among themselves than with the clinician-rated scales. Tempting though it may be to use a cut-off score on a self-report inventory as a single means of deriving a diagnosis, it is inadequate and unreliable and should be avoided.

Screening

Two quick questions from Primary Care Evaluation of Mental Disorders (PRIME-MD)[2] can provide us with a highly sensitive (94%) but not very specific (35%) screening test for depression:[3]

1. Have you been bothered by little interest or pleasure in doing things?

2. Have you been feeling down, depressed, or hopeless in the last month?

If a patient responds positively to these two questions, only four follow-up questions—on sleep disturbance, appetite change, low self-esteem, and anhedonia—are needed to confirm a diagnosis of depression. If a patient has a positive response on at least two of these four questions (Table 1), the specificity of a positive test increases to 94%.[3]

Self-rated screening tools are also available.[1] The Hospital Anxiety and Depression scale is the most widely investigated and validated scale for screening; however, it is too long and difficult to score, making it less useful in clinical practice. The 20-item Zung Depression Self-Rating Scale is less commonly used but it is in the public domain. It does not have adequate sensitivity to detect change over time, so it is not considered useful for following response to treatment.

The Geriatric Depression Scale (GDS) is a self-report measure designed to minimize the impact of somatic symptoms associated with aging and illness.[4] It has a yes/no format, and the 15-item version, using a cutoff of five, has good sensitivity and positive predictive values for diagnosis of major depression (Table 2). If a clinician is concerned about cognitive impairment, the Mini Mental State Exam (MMSE), which takes 5 minutes to administer and score, is a useful addition.[5]

Diagnosis

The full version of the PRIME-MD clinician-rated scale, available in the public domain, contains 26 yes/no questions concerning symptoms experienced in the past month, and incorporates observed and reported behavior.[2] On average, it takes 8.4 minutes to perform. If we have a clinical suspicion that a patient is depressed, the pre-test probability is close to 50%, and the post-test probability after a positive test (using a cut-off value of 5/9) becomes 94%. This is better than most of the routine laboratory tests we use daily in practice. If the score is 4/9 or less, then we need to consider other depressive disorders such as dysthymia, complicated bereavement, adjustment disorder, mixed anxiety/depression, minor depressive disorder, or premenstrual dysphoric disorder. PRIME-MD has been validated in adults and adolescents over age 13; its applicability to seniors and children is limited.

More recently, a streamlined patient self-report version of the PRIME-MD, called the Patient Health Questionnaire (PHQ) has been made available.[6] The PHQ is 3 pages long and covers the five most common psychiatric issues in primary care (depression, anxiety, alcohol, somatoform, and eating disorders). An abbreviated PHQ (the PHQ-9) for depression has been developed that reduces physician time to less than 3 minutes (Table 3).[7] The PHQ-9 also offers a severity score for each symptom, and hence can also be used to follow outcome. The PHQ-9 and other depression tools can be downloaded from the MacArthur Foundation web site (www.depression-primarycare.org [10]).

Measuring outcomes

The Hamilton Depression Rating Scale (HAM-D), the oldest, most widely used and validated instrument, has numerous versions, both clinician-rated and self-reported, as well as a computer-administered version.[8] Some versions are currently available in the public domain while others are still copyright protected. The clinician-administered versions are widely used in clinical trials for evaluating response to treatment but they require training to use, take 20 to 30 minutes to administer, and so are less useful for busy family physicians.

Many clinicians prefer to use a patient self-rated scale such as the Beck Depression Inventory (BDI, protected by copyright and requiring permission and payment of a fee to reproduce). The BDI-II is a 21-item self-report measure of the severity of depressive symptoms. It has high sensitivity and specificity and is valid and reliable in assessing the severity of depressive symptoms.[9] Among its shortcomings are its high item difficulty (requires the patient to be able to read and understand the questions) and poor discriminant validity against anxiety.

Currently, the HAM-D and the BDI are probably the best-validated scales to quantitatively assess response to treatment. Response has been defined as a 50% reduction in baseline score on the HAM-D or BDI in most clinical trials—in practice we ideally want to see our patients in remission (e.g., scores within the normal range) rather than just a 50% symptom reduction. There are shorter six- to seven-item versions of the HAM-D and the BDI, but they are not yet widely validated or used in clinical practice, and do not include some important clinical items such as sleep disturbance.

So what should I use in my office?

On a day-to-day basis, use of the two PRIME-MD screening questions followed by either the rest of the clinician-administered PRIME-MD or the self-report PHQ-9, with evaluation of both alcohol/drug consumption and anxiety by screening questions, remains the briefest, simplest, most accurate way to diagnose major depression in an adult population. Using the self-report BDI or the PHQ-9 to follow scores at baseline and designated follow-up intervals is an accurate and reliable strategy that allows us to identify those individuals who are unresponsive to treatment and/or who require further intervention or consultation. Patients can complete and score the questionnaires themselves in the waiting room prior to seeing their doctor.

Consistent use of this systematic approach to depression management can improve our diagnostic accuracy, save time, help us choose appropriate treatment interventions, and effectively monitor outcomes. This approach should also allow us to further reduce the significant burden associated with depression in primary care.

Competing interests

Dr Michalak is supported by a Canadian Institutes of Health Research/Wyeth Ayerst Canada Postdoctoral Research Fellowship.

Table 1. PRIME-MD screening questions to detect depressive symptoms (www.depression-primarycare.org/ap1.html) [11] [9]

A. Evaluation questions

1. Depressed mood: Have you felt sad, low, down, depressed, or hopeless? On a scale of 0 to 10 (0 = most depressed, 10 = least depressed), how have you been feeling lately?

2. Loss of interest: Have you lost interest or pleasure in the things you usually like to do? Have you been as social as usual? Have you been less interested in interacting with others (family, co-workers)?
If answered yes to one or both of the above symptoms, continue.

B. Symptom questions

3. Sleep disturbance: Have you been sleeping much more than usual or had difficulty falling asleep or staying asleep?

4. Appetite disturbance: Have you lost your appetite or had an unusual increase in appetite? Any cravings for junk food?

5. Loss of energy: Have you been feeling tired or having little energy?

6. Difficulty concentrating: Does your thinking seem slower or more confused than usual? Are you making more mistakes?

7. Feelings of worthlessness: Have you felt that you are a failure or that you let yourself or your family down? What are you looking forward to? Have you felt guilty about things that happened in your life?

8. Psychomotor retardation: Have you been moving or talking more slowly than usual? Have you felt agitated or on edge? Do you feel like you have to keep talking or moving all the time? (Also can be observed)

9. Suicidal thoughts (bored with life): Have you thought that you or your family would be better off if you were dead? Have you thought of killing yourself? Have you tried to hurt/kill yourself before? When? How many times? What did you do? Are you thinking of killing yourself? Do you have a plan? How will you do it? What stops you from acting on your thoughts?

Scoring

• Score one point for each positive category.

• Cut-off value is 5/9, but patients who answer positively to suicide questions are at high risk and need urgent attention. Observed and reported behavior should be incorporated into the evaluation.

• If the individual has experienced five or more symptoms for at least 2 weeks, diagnosis is major depressive disorder. If less than five symptoms are present, consider other depressive disorders.

Table 2. Geriatric Depression Scale—GDS, Short Form (www.stanford.edu/~yesavage/GDS.html [12]) [4]

Choose the best answer for how you have felt over the past week:
1. Are you basically satisfied with your life?	Yes	No
2. Have you dropped many of your activities and interests?	Yes	No
3. Do you feel that your life is empty?	Yes	No
4. Do you often get bored?	Yes	No
5. Are you in good spirits most of the time?	Yes	No
6. Are you afraid that something bad is going to happen to you?	Yes	No
7. Do you feel happy most of the time?	Yes	No
8. Do you often feel helpless?	Yes	No
9. Do you prefer to stay at home, rather than going out and doing new things?	Yes	No
10. Do you feel you have more problems with memory than most?	Yes	No
11. Do you think it is wonderful to be alive now?	Yes	No
12. Do you feel pretty worthless the way you are now?	Yes	No
13. Do you feel full of energy?	Yes	No
14. Do you feel that your situation is hopeless?	Yes	No
15. Do you think that most people are better off than you?	Yes	No
Scoring
“No” to questions 1, 5, 7, 11, 13; “Yes” to other questions Score: ____/15 Normal is 0–5; scores above 5 suggest depression

Table 3. Patient Health Questionnaire–PHQ-9 www.depression-primarycare.org/ap1.html [11].).[7]

Patient name: _________________________________ Date:________________________

Over the last 2 weeks, how often have you been bothered by any of the following problems?

Not at all (0)

Several days (1)

More than half the days (2)

Nearly every day (3)

a. Little interest or pleasure in doing things.

b. Feeling down, depressed, or hopeless.

c. Trouble falling/staying asleep, sleeping too much.

d. Feeling tired or having little energy.

e. Poor appetite or overeating.

f. Feeling bad about yourself, or that you are a failure, or have let yourself or your family down.

g. Trouble concentrating on things, such as reading the newspaper or watching TV.

h. Moving or speaking so slowly that other people could have noticed.
Or the opposite; being so fidgety or restless that you have been moving around more than usual.

i. Thoughts that you would be better off dead or of hurting yourself in some way.

If you checked off any problem on this questionnaire so far, how difficult have these problems made it for you to do your work, take care of things at home, or get along with other people?

Not difficult at all Somewhat difficult Very difficult Extremely difficult

Scoring

Total score: _____________
Instructions—How to score the PHQ-9
• Major depressive disorder is suggested if:
- Of the nine items, five or more are checked as at least “more than half the days”
- Either item a. or b. is positive, that is, at least “more than half the days”
• Other depressive syndrome is suggested if:
- Of the nine items, a., b., or c. are checked as at least “more than half the days”
- Either item a. or b. is positive, that is, at least “more than half the days”
• Also, PHQ-9 scores can be used to plan and monitor treatment. To score the instrument, tally each response by the number value under the answer headings, (not at all = 0, several days = 1, more than half the days = 2, and nearly every day = 3). Add the numbers together to total the score on the bottom of the questionnaire. Interpret the score by using the guide listed below.

Guide for interpreting PHQ-9 scores

Score	Action
0–4	Suggests the patient may not need depression treatment.
5–14	Mild major depressive disorder. Physician uses clinical judgment about treatment, based on patient’s duration of symptoms and functional impairment.
15–19	Moderate-major depressive disorder. Warrants treatment for depression, using antidepressant, psychotherapy, or a combination of treatment.
20 or higher	Severe major depressive disorder. Warrants treatment with antidepressant, with or without psychotherapy; follow frequently.

Functional health assessment
The instrument also includes a functional health assessment, asking the patient how emotional difficulties or problems impact work, things at home, or relationships with other people. The responses “very difficult,” or “extremely difficult” suggest that the patient’s functionality is impaired. After treatment begins, functional status and number score can be measured to assess patient improvement.

Free screening tools listed in this article

www.depression-primarycare.org/ap1.html [11]. Patient Health Questionnaire (PHQ-9), screening questions, and PRIME-MD questions.

www.stanford.edu/~yesavage/GDS.html [12]. Geriatric Depression Scale–GDS, Short Form

This article has been peer reviewed.

References

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2. Spitzer RL, Williams JB, Kroenke K, et al. Utility of a new procedure for diagnosing mental disorders in primary care. The PRIME-MD 1000 study. JAMA 1994;272:1749-1756. PubMed Abstract [13]
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5. Cockrell JR, Folstein MF. Mini-Mental State Examination (MMSE). Psychopharmacol Bull 1988;24:689-692. PubMed Citation [16]
6. Spitzer RL, Kroenke K, Williams JB. Validation and utility of a self-report version of PRIME-MD: The PHQ primary care study. Primary Care Evaluation of Mental Disorders. Patient Health Questionnaire. JAMA 1999;282:1737-1744. PubMed Abstract [17]
7. Kroenke K, Spitzer RL, Williams JB. The PHQ-9: Validity of a brief depression severity measure. J Gen Intern Med 2001;16:606-613. PubMed Abstract [18]
8. Bech P, Hamilton M, Zung WWK. The Bech, Hamilton, and Zung Scales for Mood Disorders: Screening and Listening 2nd ed. New York, NY: Springer-Verlag, 1996. 63 pp.
9. Arnau RC, Meagher MW, Norris MP, et al. Psychometric evaluation of the Beck Depression Inventory-II with primary care medical patients. Health Psychol 2001;20:112-119. PubMed Abstract [19]

Dr Anderson is a family physician in Sooke, British Columbia. Dr Michalak is a postdoctoral research fellow in the Division of Clinical Neuroscience, Department of Psychiatry, UBC. Dr Lam is professor and head of the Division of Clinical Neuroscience, Department of Psychiatry at UBC and director of the Mood Disorders Centre at UBC Hospital.