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Spitzer RL, Kroenke K, Williams JBW, and the Patient Health Questionnaire Primary Care Study Group. Validation and Utility of a Self-report Version of PRIME-MDThe PHQ Primary Care Study. JAMA. 1999;282(18):1737–1744. doi:10.1001/jama.282.18.1737
Context The Primary Care Evaluation of Mental Disorders (PRIME-MD) was developed
as a screening instrument but its administration time has limited its clinical
Objective To determine if the self-administered PRIME-MD Patient Health Questionnaire
(PHQ) has validity and utility for diagnosing mental disorders in primary
care comparable to the original clinician-administered PRIME-MD.
Design Criterion standard study undertaken between May 1997 and November 1998.
Setting Eight primary care clinics in the United States.
Participants Of a total of 3000 adult patients (selected by site-specific methods
to avoid sampling bias) assessed by 62 primary care physicians (21 general
internal medicine, 41 family practice), 585 patients had an interview with
a mental health professional within 48 hours of completing the PHQ.
Main Outcome Measures Patient Health Questionnaire diagnoses compared with independent diagnoses
made by mental health professionals; functional status measures; disability
days; health care use; and treatment/referral decisions.
Results A total of 825 (28%) of the 3000 individuals and 170 (29%) of the 585
had a PHQ diagnosis. There was good agreement between PHQ diagnoses and those
of independent mental health professionals (for the diagnosis of any 1 or
more PHQ disorder, κ = 0.65; overall accuracy, 85%; sensitivity, 75%;
specificity, 90%), similar to the original PRIME-MD. Patients with PHQ diagnoses
had more functional impairment, disability days, and health care use than
did patients without PHQ diagnoses (for all group main effects, P<.001). The average time required of the physician to review the
PHQ was far less than to administer the original PRIME-MD (<3 minutes for
85% vs 16% of the cases). Although 80% of the physicians reported that routine
use of the PHQ would be useful, new management actions were initiated or planned
for only 117 (32%) of the 363 patients with 1 or more PHQ diagnoses not previously
Conclusion Our study suggests that the PHQ has diagnostic validity comparable to
the original clinician-administered PRIME-MD, and is more efficient to use.
Mental disorders in primary care are common, disabling, costly, and
However, they are frequently unrecognized and therefore not treated.2-6
Although there have been many screening instruments developed,7,8
PRIME-MD (Primary Care Evaluation of Mental Disorders)5
was the first instrument designed for use in primary care that actually diagnoses
specific disorders using diagnostic criteria from the Diagnostic
and Statistical Manual of Mental Disorders, Revised Third Edition9(DSM-III-R) and Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition10(DSM-IV).
PRIME-MD is a 2-stage system in which the patient first completes a
26-item self-administered questionnaire that screens for 5 of the most common
groups of disorders in primary care: depressive, anxiety, alcohol, somatoform,
and eating disorders. In the original study,5
the average amount of time spent by the physician to administer the clinician
evaluation guide to patients who scored positively on the patient questionnaire
was 8.4 minutes. However, this is still a considerable amount of time in the
primary care setting, where most visits are 15 minutes or less.11
Therefore, although PRIME-MD has been widely used in clinical research,12-28
its use in clinical settings has apparently been limited. This article describes
the development, validation, and utility of a fully self-administered version
of the original PRIME-MD, called the PRIME-MD Patient Health Questionnaire
(henceforth referred to as the PHQ).
The 2 components of the original PRIME-MD, the patient questionnaire
and the clinician evaluation guide, were combined into a single, 3-page questionnaire
that can be entirely self-administered by the patient (it can also be read
to the patient, if necessary). The clinician scans the completed questionnaire,
verifies positive responses, and applies diagnostic algorithms that are abbreviated
at the bottom of each page. In this study, the data from the questionnaire
were entered into a computer program that applied the diagnostic algorithms
(written in SPSS 8.0 for Windows [SPSS Inc, Chicago, Ill]). The computer program
does not include the diagnosis of somatoform disorder, because this diagnosis
requires a clinical judgment regarding the adequacy of a biological explanation
for physical symptoms that the patient has noted.
A fourth page has been added to the PHQ that includes questions about
menstruation, pregnancy and childbirth, and recent psychosocial stressors.
This report covers only data from the diagnostic portion (first 3 pages) of
the PHQ. Users of the PHQ have the choice of using the entire 4-page instrument,
just the 3-page diagnostic portion, a 2-page version (Brief PHQ) that covers
mood and panic disorders and the nondiagnostic information described above,
or only the first page of the 2-page version (covering only mood and panic
disorders) (Figure 1).
The original PRIME-MD assessed 18 current mental disorders. By grouping
several specific mood, anxiety, and somatoform categories into larger rubrics,
the PHQ greatly simplifies the differential diagnosis by assessing only 8
disorders. Like the original PRIME-MD, these disorders are divided into threshold
disorders (corresponding to specific DSM-IV diagnoses,
such as major depressive disorder, panic disorder, other anxiety disorder,
and bulimia nervosa) and subthreshold disorders (in which the criteria for
disorders encompass fewer symptoms than are required for any specific DSM-IV diagnoses: other depressive disorder, probable alcohol
abuse or dependence, and somatoform and binge eating disorders).
One important modification was made in the response categories for depressive
and somatoform symptoms that, in the original PRIME-MD, were dichotomous (yes/no).
In the PHQ, response categories are expanded. Patients indicate for each of
the 9 depressive symptoms whether, during the previous 2 weeks, the symptom
has bothered them "not at all," "several days," "more than half the days,"
or "nearly every day." This change allows the PHQ to be not only a diagnostic
instrument but also to yield a measure of depression severity that can be
of aid in initial treatment decisions as well as in monitoring outcomes over
time. Patients indicate for each of the 13 physical symptoms whether, during
the previous month, they have been "not bothered," "bothered a little," or
"bothered a lot" by the symptom. Because physical symptoms are so common in
primary care, the original PRIME-MD dichotomous-response categories often
led patients to endorse physical symptoms that were not clinically significant.
An item was added to the end of the diagnostic portion of the PHQ asking
the patient if he or she had checked off any problems on the questionnaire:
"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?" As with the original PRIME-MD,
before making a final diagnosis, the clinician is expected to rule out physical
causes of depression, anxiety and physical symptoms, and, in the case of depression,
normal bereavement and history of a manic episode.
Our major purpose was to test the validity and utility of the PHQ in
a multisite sample of family practice and general internal medicine patients
by answering the following questions:
Are diagnoses made by the PHQ as accurate as diagnoses
made by the original PRIME-MD, using independent diagnoses made by mental
health professionals (MHPs) as the criterion standard?
Are the frequencies of mental disorders found by
the PHQ comparable to those obtained in other primary care studies?
Is the construct validity of the PHQ comparable
to the original PRIME-MD in terms of functional impairment and health care
Is the PHQ as effective as the original PRIME-MD
in increasing the recognition of mental disorders in primary care patients?
How valuable do primary care physicians find the
diagnostic information in the PHQ?
How comfortable are patients in answering the questions
on the PHQ, and how often do they believe that their answers will be helpful
to their physicians in understanding and treating their problems?
The study was conducted at 8 primary care sites (5 general internal
medicine and 3 family practice). The institutional review board of each site
approved the study protocol.
From May 1997 to November 1998, 3890 patients, 18 years or older, were
invited to participate in the study. There were 190 who declined to participate,
266 who started but did not complete the questionnaire, and 434 whose questionnaires
were not entered into the data set because either more than 1 page was not
completed or there were inadequate data to rule in or out 1 or more PHQ diagnoses.
This resulted in the 3000 cases reported here (1578 family practice, 1422
general internal medicine). All sites used 1 of 2 subject selection methods
to minimize sampling bias: selection of either consecutive patients for a
given clinic session or every nth patient until the
intended quota for that session was achieved.
Before seeing their physicians, all patients completed PHQs. Additionally,
they completed items regarding physician visits and disability days during
the previous 3 months, their comfort with answering the PHQ questions, and
how valuable they believed the PHQ would be to their physicians in understanding
and treating the problems they were having. In addition, each patient completed
the Medical Outcomes Study Short-Form General Health Survey (SF-20),29 which measures functional status in 6 dimensions.
A total of 62 physicians participated in the study (21 general internal
medicine, 41 family practice [19 of whom were family practice residents]).
Their mean (SD) age was 37 (6.5) years, and 63% were male.
After evaluating each patient but before reviewing the PHQ, the physician
noted whether the patient was new or established, the physician's knowledge
of any current mental disorders, and types of current physical disorders (hypertension,
heart disease, diabetes, liver disease, renal disease, arthritis, pulmonary
disease, cancer, or other). The physician then reviewed the PHQ and asked
any additional questions necessary to clarify responses on the questionnaire.
Also noted were any treatments or referrals for mental disorders that were
being initiated or planned during that particular visit. Midway through the
study, physicians noted how long it took them to review each PHQ and ask clarifying
questions. Finally, at the conclusion of the study, all physicians completed
confidential questionnaires asking them about the value and usefulness of
To determine the agreement of PHQ diagnoses with those of MHPs, midway
through the study an MHP (a PhD clinical psychologist or 1 of 3 senior psychiatric
social workers) attempted to interview by telephone all subsequently entered
subjects who had a telephone, agreed to be interviewed, and could be contacted
within 48 hours. All except 1 site participated in these validation interviews.
The MHP was blinded to the results of the PHQ. The rationale and additional
details of the MHP telephone interview, which used the overview from the Structured
Clinical Interview for DSM-III-R30
and diagnostic questions from the original PRIME-MD, are described in the
original PRIME-MD report.5
The mean (SD) age of the patients was 46 (17.2) years, with a range
of 18 to 99 years; 66% were female; 79% were white (not Hispanic), 13% were
African American, 4% were Hispanic; 48% were married, 12% were divorced, 23%
were never married; and 25% were college graduates. There was considerable
site variability (site ranges: mean age, 40-62 years; female, 54%-89%; college
graduate, 2%-50%). Of the total sample, 80% were established clinic patients,
and the remainder were being seen for the first time. The most common types
of physical disorders were hypertension (25%), arthritis (11%), diabetes (8%),
and pulmonary disease (7%).
The 585 subjects who had an MHP interview within 48 hours of completing
the PHQ were, within each site, similar to patients not reinterviewed in terms
of demographic profile, functional status, and frequency of psychiatric diagnoses.
One modification from the original PRIME-MD algorithm was necessary. The number
of symptoms required for diagnosing major depressive disorder could remain
the same as in DSM-IV, ie, 5 of 9 during the previous
2 weeks. However, because the PHQ response set was expanded from the simple
yes/no in the original PRIME-MD to 4 frequency levels as described above,
lowering the PHQ threshold from "nearly every day" to "more than half the
days" considerably improved sensitivity (from 37% to 73%) while maintaining
high specificity (94%).
The operating characteristics of the PHQ are generally satisfactory
and comparable to those obtained in the original PRIME-MD study (Table 1). Of note, the sensitivity of the
PHQ for major depressive disorder was somewhat higher (73% vs 57%). As in
the original study, the prevalences for PHQ diagnoses and MHP diagnoses were
nearly identical, indicating that the PHQ did not have a systematic tendency
to overdiagnose or underdiagnose any psychiatric disorder.
We also examined agreement between the PHQ results and the MHP on a
computer-derived index of depression symptom severity (the sum of the scores
for the 9 PHQ– or MHP–recorded depressive symptoms; possible range,
0-27). The correlation between the PHQ and MHP for this index was 0.84.
Overall, 28% of the subjects had a PHQ diagnosis, of which 15% had a
threshold diagnosis and 13% a subthreshold diagnosis only (Table 2). The overall prevalence of psychiatric disorder was somewhat
lower than in the original study (28% vs 39%). The proportion of patients
with a psychiatric disorder who had more than 1 disorder was also somewhat
lower (36% vs 56%). As in the original PRIME-MD study, the prevalence varied
considerably across sites, which, at least in part, is undoubtedly attributable
to significant differences in patient demographic variables across the sites.
The physician time required to review the PHQ (n = 1527) was less than
1 minute for 42% of the subjects, 1 to 2 minutes for 43%, 3 to 5 minutes for
13%, and more than 5 minutes for only 3%. Thus, the time required of the physician
to review the PHQ is far less than the time to administer the clinician-administered
PRIME-MD (less than 3 minutes for 85% of the subjects given the PHQ vs 16%
of the subjects given the PRIME-MD in our original study).
Figure 2 shows the mean scores
on the 6 scales of the SF-20 for 4 groups of subjects. Each of the disorders
(except for alcohol abuse) has 1, 2, or 3 symptoms that must be present for
the diagnosis to be made (eg, depressed mood or loss of interest for major
depressive disorder). Patients who did not endorse any of these required symptoms
on the PHQ were considered to be symptom–screen negative. Patients who
had 1 or more of these required symptoms but did not qualify for a subthreshold
or threshold diagnosis were considered to be symptom–screen positive
but to have no psychiatric diagnosis. The third and fourth groups met criteria
for subthreshold and any threshold diagnoses, respectively. Scores were adjusted
by analysis of covariance for number of physical disorders, sex, age, minority
status, education level, and site. As with the original PRIME-MD study, the
symptom–screen negative group had the highest level of functioning on
all of the scales, followed by the symptom–screen positive group, the
subthreshold group, and, finally, the threshold group. The group main effects
were all significant (P<.001). Table 3 presents the mean values on 1 index of health care use and
1 of disability in the same 4 groups, with initial scores again adjusted for
the variables just noted. As in the original PRIME-MD study, the same pattern
of increasing use and disability is seen from the symptom–screen negative
group to the threshold psychiatric diagnoses group, and the group main effects
were all significant (P<.001).
We also examined how the probability of a subthreshold or threshold
PHQ diagnosis varied depending on responses to the question: "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?" The percentage of subjects with a PHQ
diagnosis varied significantly (P<.001), ranging
from 17% of the subjects who responded "not difficult at all," to 38% who
responded "somewhat difficult," to 69% who responded "very difficult," to
91% who responded "extremely difficult." This question was also associated
with functional impairment: the mean correlation of this item with each of
the 6 SF-20 scales was 0.38, ranging from 0.27 for pain to 0.53 for mental
health. We also found that the computer-derived index of depression severity
had high correlations with the SF-20 scales (mean correlation was 0.49, ranging
from 0.33 for pain to 0.73 for mental health).
Of the 803 patients with a PHQ diagnosis, 46% (n = 368) had not been
recognized by their physicians as having any diagnosis included in the PHQ
system after being clinically evaluated but before physician review of the
PHQ (Table 4). The nonrecognition
rate was even higher for specific diagnostic categories. The ability of the
PHQ to detect a substantial number of unrecognized cases is comparable to
that of the original PRIME-MD.
At the conclusion of the study, most physicians reported that the diagnostic
information provided by the PHQ was "very" (46%) or "somewhat" (41%) useful
in management and treatment planning. The majority (80%) also reported that
if they were able to have the clerical staff in their setting give the questionnaire
to patients, it would be helpful if given routinely to all new patients, all
patients who had not received a questionnaire in the last year, and to any
patient for whom it seemed indicated at the time of the visit. Prior to the
study, nearly half (48%) of the physicians acknowledged that they only "occasionally"
asked their patients about many of the diagnostic symptoms included in the
PHQ when their chief complaint did not suggest a mental disorder.
Although our study was designed to test the diagnostic validity of the
PHQ and not to influence treatment decisions, we still asked the physicians,
for each case, what treatment or referral actions they initiated or planned
to initiate for any problems reported in the PHQ. There were 363 patients
with 1 or more PHQ diagnoses who had not been previously determined by their
physicians to have any PHQ diagnoses and for whom information on treatment
decisions was available. For only 32% (n = 117) did physicians note that any
new management actions were initiated or planned. For only 16% (n = 58) were
follow-up visits planned; for only 3% (n = 11) were antidepressants prescribed;
and for only 3% (n = 11) were referrals to MHPs provided. Of the 74 patients
with PHQ diagnoses of major depression that had not previously been recognized,
follow-up visits, antidepressant prescriptions, or mental health referrals
were noted for only 22%, 10%, and 5% of the cases, respectively.
The majority (88%) of patients said they were "very" or "somewhat" comfortable
answering the questions on the PHQ. Likewise, 89% believed that the questions
were "very" or "somewhat" helpful in getting their physicians to better understand
or treat the problems they were having.
The self-administered PHQ has diagnostic validity comparable to that
of the original clinician-administered instrument. This was demonstrated both
by agreement with an independent MHP interview (criterion validity) as well
as by the strong association of PHQ diagnoses with indices of functional impairment
and health care use (construct validity). As with the original PRIME-MD, most
patients were comfortable answering questions and judged the information to
be valuable to their physicians. Most physicians also found it useful and
thought it would be helpful if used routinely. The PHQ is efficient, requiring
much less of a clinician's time than the original PRIME-MD.
In addition to its value in yielding provisional psychiatric diagnoses,
the PHQ yields an index of depressive symptom severity. This index, which
had a remarkably high correlation with an MHP assessment of the same dimension,
may be useful in initial management decisions as well as monitoring treatment
outcome in depressed patients.
Previous self-report instruments used in primary care for case finding
or screening yield indices of severity rather than categorical psychiatric
diagnoses.6,7 The PHQ is the first
entirely self-administered diagnostic instrument designed for use in primary
care. We found that agreement between the PHQ diagnosis of major depressive
disorder and the MHP diagnosis was maximized when the frequency threshold
for the individual major depression items of the PHQ was lowered from the DSM-IV requirement of "nearly every day" to "more than
half the days." This finding may be due to the fact that in most structured
diagnostic interviews, such as the Structured Clinical Interview for DSM-III-R and the interview used by our MHPs, patients
who acknowledge depressive symptoms are asked, for each symptom, whether it
has been present "nearly every day." Given only this dichotomous choice, many
patients whose symptoms have been present only "more than half the days" during
the time period being considered may respond affirmatively, believing that
to be their only opportunity to indicate that they frequently have had the
symptom in question. Many patients with major depressive disorder diagnosed
by the PHQ who reported on the questionnaire that the symptoms were present
only "more than half the days" did answer affirmatively to the MHP when asked
if the symptom had been present "nearly every day." The implication of this
finding is that a well-designed self-report instrument, which allows the subject
to consider a range of frequency responses for symptoms, may yield a more
accurate assessment of frequency than a clinician-administered structured
interview, which, for efficiency of administration, presents a dichotomous
choice of a single frequency taken from a diagnostic criterion.
An especially interesting finding in our study is the strong predictive
value of the question at the end of the PHQ: "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?" This global self-assessment of the degree of impairment
associated with the patient's psychological symptoms is a potent indicator
of the likelihood of a psychiatric diagnosis and of functional impairment.
Several possible limitations in the study should be noted. The PHQ was
scored with a computer program to ensure that the diagnostic algorithms were
applied correctly. In pilot testing the questionnaire, we found that clinicians
who had little training in applying the algorithms sometimes made errors.
Our study does not indicate how much training is necessary in different primary
care settings to ensure that the diagnostic algorithms are applied with minimal
errors. Also, as with any diagnostic test, the PHQ does not detect all cases
of mental disorders. Therefore, clinicians should ask additional questions
of patients who they feel may have "false-negative" PHQ results.
Although the PHQ is clearly more efficient for clinicians to use than
the original PRIME-MD, our study indicates that it may also be easier for
clinicians to ignore. In our study, the PHQ had less impact on physician therapeutic
actions than did the original PRIME-MD, which requires that clinicians gather
much of the diagnostic information through direct interview. This may lead
to more intimate and detailed awareness and understanding of their patients'
symptoms than simply reviewing a self-report questionnaire. This, in turn,
might increase the likelihood of initiating some form of treatment or referral.
Our study confirms what has been demonstrated in numerous other studies31-33: merely providing
clinicians with information about psychiatric diagnoses has only a moderate
impact on their behavior. The relatively weak effect of information alone
on producing changes in clinical practice is not unique to mental disorders
but is also true for medical conditions in general.34
Aside from improved detection, what is also required to improve the management
and outcomes of patients with mental disorders in primary care are system
changes, such as longer or more frequent visits, collaborative support from
MHPs, and better reimbursement for psychosocial evaluation and treatment.35-39
Ideally, the PHQ would be administered in clinical practice to all new
patients, patients in whom a psychiatric diagnosis is suspected, and established
patients on a periodic basis (eg, annually), as is done with other screening
procedures. In contrast, because of the length of time required to administer
the original PRIME-MD, it has been used primarily as a research tool; clinicians
have predominantly used it only with patients in whom they already suspected
a psychiatric diagnosis—rather than using it routinely to detect unrecognized
The original PRIME-MD study5 demonstrated
that primary care physicians could make valid psychiatric diagnoses with the
aid of brief, structured interviews. From the perspective of psychiatric assessment
in primary care, our current study demonstrates that a well-designed self-report
questionnaire can also provide comparably valid diagnoses. The original PRIME-MD
has been widely used in primary care research, and we expect that the PHQ
may offer an advantage in future studies because of its comparable validity
but greater efficiency. With proper integration into primary care practice,
accompanied by other system changes, the PHQ could become a useful clinical
adjunct to improve the recognition and management of mental disorders.
Major depressive syndrome is indicated if answers to #1a or b and five
or more of #1a-i are at least "More than half the days" (count #1i if present
at all); other depressive syndrome, if #1a or b and two, three, or four of
#1a-i are at least "More than half the days" (count #1i if present at all);
panic syndrome, if all of #2a-e are "YES."