The real-world health resource use and costs of misdiagnosing bipolar I disorder

Background: Misdiagnosis of bipolar I disorder (BP-I) as major depressive disorder (MDD) is common. This study evaluated healthcare resource utilization (HRU) and costs among BP-I patients who were initially misdiagnosed with MDD (misdiagnosed BP-I cohort) versus patients diagnosed with BP-I without a known prior MDD diagnosis (BP-I only cohort).

Methods: Data from IBM® MarketScan® Research Databases were used. The index date was the first MDD diagnosis for misdiagnosed patients or first BP-I diagnosis for BP-I only patients. Inverse probability of treatment weighting was used to balance baseline characteristics between cohorts. All-cause and mental health (MH)-related HRU and costs were compared between weighted cohorts using rate ratios (RRs) and mean cost differences, respectively. Outcomes were reported per patient-year (PPY). Confidence intervals and P-values were calculated using non-parametric bootstrap procedures.

Results: Overall, 14,729 misdiagnosed BP-I and 16,072 BP-I only patients met criteria. Baseline characteristics were balanced across weighted cohorts. Misdiagnosed BP-I patients had significantly higher rates of hospitalizations, emergency room visits, and outpatient visits than BP-I only patients during follow-up (all-cause RRs: 1.94, 1.33, and 1.38, respectively, all P < .001; MH-related RRs: 2.19, 1.77, and 1.77, respectively, all P < .001). Similarly, misdiagnosed BP-I patients incurred significantly higher total healthcare costs PPY over follow-up (all-cause: $21,202 vs $14,661, cost difference = $6541; MH-related: $12,901 vs $6749, cost difference = $6152; both P < .001). Cost differences were even higher during the first year (all-cause = $7146; MH-related = $6619; both P < .001).

Limitations: Claims database (e.g., coding inaccuracies); generalizability to uninsured patients.

Conclusions: The prompt and correct diagnosis of BP-I may significantly reduce HRU and costs.