Distinguishing Bipolar Major Depression From Unipolar Major Depression With the Screening Assessment of Depression-Polarity (SAD-P)
J Clin Psychiatry 2006;67:434-442
© Copyright 2014 Physicians Postgraduate Press, Inc.
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Background: Patients with bipolar I or II
major depression are often misdiagnosed with unipolar
major depression. The goal of this study was to
develop and validate a brief instrument to screen for
bipolar disorder in patients actively ill with major
Method: The sample consisted of subjects
who enrolled in the National Institute of Mental
Health-Collaborative Program on the Psychobiology of
Depression-Clinical Studies from 1978 to 1981
during an episode of major depression and included 91
subjects with bipolar I major depression, 52 with
bipolar II major depression, and 338 with unipolar
major depression diagnosed according to Research
Diagnostic Criteria. Most of the subjects were
inpatients at the time of enrollment, and subjects were
prospectively followed for up to 20 years. In order to
create, test, and cross-validate the screening instrument,
a split-sample data analytic procedure was
performed. This procedure yielded 3 groups of subjects: the
bipolar I index sample, the bipolar I
cross-validation sample, and the bipolar II cross-validation
sample. Each group included subjects with bipolar major
depression and subjects with unipolar major depression. Within the bipolar I index sample, subjects
with bipolar I major depression at study intake were
compared with subjects with unipolar major
depression at study intake on a pool of 59
sociodemographic and clinical candidate variables. The 3
variables showing the greatest disparity between bipolar I
subjects and unipolar subjects were selected for
the screen, the Screening Assessment of Depression-Polarity (SAD-P). The operating characteristics
of the SAD-P were then examined within the bipolar
I index sample, bipolar I cross-validation sample,
and bipolar II cross-validation sample.
Results: The items selected for the screening
instrument were (1) presence of delusions during
the current episode of major depression, (2) number
of prior episodes of major depression, and (3)
family history of major depression or mania. The
screen identified bipolar major depression with a
sensitivity of 0.82 in the bipolar I index sample, 0.72 in the
bipolar I cross-validation sample, and 0.58 in the
bipolar II cross-validation sample. With regard to misclassifying subjects with unipolar major
depression, the screen provided a positive predictive
value of 0.36 in the bipolar I index sample, 0.29 in the
bipolar I cross-validation sample, and 0.27 in the
bipolar II cross-validation sample.
Conclusion: We suggest using the 3-item
SAD-P as a preliminary screen for bipolar disorder in
patients who present with an active episode of