| |
QS-20 User's Guide
Overview |
|
| The Quick Screen-20 (QS-20) is a 20 item
case finding tool that can be self-administered in less
than two minutes. The test contains a 10 item depression
scale, a 10 item anxiety scale, and a Global Severity
Index (GSI) based on all 20 items. All items use a
True/False response format, designed to simplify test
administration and minimize response time. The items are
a subset of the items contained in the Shedler QPD
Panel and have undergone extensive testing for both
physician and patient acceptance1,2.
Readability of the test items is at the 6th grade level.
The items comprising the QS-20 depression and anxiety
scales are reproduced in Tables 1 and 2 below.
|
top of page
|
Reliability and Validity |
|
QS-20 scale scores were validated against the
QPD Panel Depression and Anxiety scales in a
community sample of N=475 respondents. The QPD
Panel scales have demonstrated strong validity in
medical settings1,2. The cross-validated
correlation between the QS-20 depression scale and the
full QPD Panel depression scale is .91. The
cross-validated correlation between the QS-20 anxiety
scale and the full QPD Panel anxiety scale is
.90. The QS-20 depression scale also correlated highly
with the Hamilton Depression Inventory (r=.84) in a
mental health sample of N=172 respondents3.
These correlations are statistically significant
(ps<.0001) and near the theoretical maximums
permitted by the scale reliabilities, indicating strong
convergent validity.
Reliabilities (coefficient
Alpha) for the QS-20 depression, anxiety, and GSI scales
are .77, .73, and .84, respectively. |
top of page
|
Norms and Cut-Points |
|
Population norms were established in a community
sample of N=475 respondents, 69.3% male and 30.7%
female. Prevalence rates for psychiatric disorders in
the normative sample were comparable to prevalence rates
in the U.S. population. Because we observed no
significant differences between male and female
respondents, the QS-20 uses the same population norms
for males and females.
Raw scale scores are
computed by summing True responses to the relevant scale
items. The raw scores may range from 0–10 for the
Depression and Anxiety scales, and 0-20 for the GSI
scale. Test results are reported in the form of t-scores
(mean=50, standard deviation=10) and percentile
scores.
The criterion for “caseness” may be
established by the test user depending on the
requirements of the screening situation. The default
criterion for caseness is a t-score of 60 or higher (one
standard deviation above the mean, or 84th
percentile) on any QS-20 scales (depression, anxiety, or
GSI). If a patient reports suicidal ideation, the words
“SUICIDAL IDEATION” will appear on the report.
|
top of page
|
Diagnostic Decision Guidelines
|
|
If depression t-score is >= 60, consider mood
disorder
If anxiety t-score is >= 60,
consider anxiety disorder.
If depression t-score
is >= 60 and anxiety t-score is >= 60, consider
mood disorder with anxiety symptoms.
If anxiety
t-score is >= 60 and item 20 is endorsed (“I have
panic attacks where I suddenly become frightened or
anxious, and suddenly develop a lot of physical
symptoms”), consider panic disorder. |
top of page
|
Disclaimer |
|
| The results of the QS-20 are not and should not
be considered to be a diagnosis. Rather, such results
are only one factor to be evaluated by a trained
healthcare professional, in his or her expert judgment,
in making a decision about a diagnosis or deciding on a
course of treatment of any individual screened using the
QS-20. A lack of information or indications from the
QS-20 should not be construed as an indication or proof
that any condition is not present. Further or additional
tests, information and investigation may be necessary or
advisable to confirm or disaffirm any preliminary
information produced by the QS-20. |
top of page
|
TABLE 1. QS-20 Depression Items
|
|
I feel sad or depressed.
I find little or no interest or pleasure in my daily
activities.
I don’t get any real satisfaction out of anything
anymore.
I feel I have nothing to look forward to in
life.
I have trouble falling asleep or staying asleep.
I just can’t seem to get myself “going.”
I feel tired or fatigued most of the time.
I feel I cannot think or concentrate as well as I
used to.
I feel like a failure.
I think about killing myself.
|
top of page
|
TABLE 2. QS-20 Anxiety Items |
|
I often feel nervous for no good reason.
I worry about things that I know are not likely to
happen.
I often worry about things I should not have done or
said.
I sometimes get so anxious that I tremble or
shake.
I worry too long after an embarrassing
situation.
I am usually worried about several things all at
once.
I am easily “rattled” at critical moments.
My mouth is often dry.
I often feel dizzy or lightheaded for no good
reason.
I have panic attacks where I suddenly become
frightened or anxious, and suddenly develop a lot of
physical symptoms. |
top of page
|
References |
|
1Shedler J. The Shedler Quick
PsychoDiagnostics Panel (QPD Panel): A psychiatric “lab
test” for primary care. In M. Maruish (Ed.), Handbook
of Psychological Assessment in Primary Care
Settings. NY: Erlbaum;
2000.
2Shedler J, Beck A, Bensen S.
Practical mental health assessment in primary care:
validity and utility of the Quick PsychoDiagnostics
Panel. J Fam Pract.
2000;49:614-621.
3Reynolds WM &
Kobak, KA. Hamilton Depression Inventory: a self-report
version of the Hamilton Depression Rating Scale. Odessa
FL: Psychological Assessment Resources, 1995.
|
top of page
| | | |
igital Diagnostics inc |
address: 11102 Cooper Drive, Littleton, CO 80127 | phone: 800.559.9885 | email: getinfo
digitaldiagnostics.com
