Diagnosis of Unipolar Depression Following Initial Identification of Bipolar Disorder: A Common and Costly Misdiagnosis
J Clin Psychiatry 2008;69(5):749-758
© Copyright 2014 Physicians Postgraduate Press, Inc.
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Background: Bipolar disorder is challenging to diagnose in
Objectives: Our objectives were (1) to determine the rate of
depression misdiagnosis in patients previously diagnosed with bipolar disorder
in administrative claims, (2) to determine the resulting increased treatment
costs, and (3) to verify the misdiagnoses in the medical charts for a subset of
Method: We employed cohort analysis using claims from a large,
commercial, U.S. health plan from January 2001 through December 2003. Inclusion
criteria included 2 bipolar disorder diagnoses (ICD-9-CM criteria), continuous
enrollment for 1 year before and after initial bipolar disorder diagnosis, age
18-64 years, and a pharmacy benefit. Propensity scoring was used to control for
differences between patients with and without 2 depression diagnoses in the
year following their bipolar disorder diagnosis. Medical charts were obtained
for 100 patients, including 76 with a bipolar disorder diagnosis chart from one
provider and a depression diagnosis chart from a second provider.
Results: Of 3119 bipolar disorder patients meeting inclusion
criteria, 857 (27.5%) had subsequent depression misdiagnoses during the
follow-up year. These patients had 1.82 times more psychiatric hospitalizations
and 2.47 times more psychiatric emergency room visits. For 673 patients
(78.5%), a different provider gave the depression misdiagnosis. Annual
per-patient treatment costs were significantly higher (p < .001) for those
diagnosed with depression ($12,594) than for those not ($9405). In the chart
review, both the bipolar disorder and subsequent depression diagnoses were
confirmed for 65.8% (50/76) of the patients who had charts from 2 different
Conclusions: More than one quarter of individuals diagnosed
with bipolar disorder received an ostensible depression misdiagnosis during the
follow-up period. Significant (p = .001) increases in psychiatric inpatient
hospitalization suggest that improvements in the continuity of care could
improve outcomes and reduce costs.