The Swedish bipolar collection (SWEBIC).

Background: The Swedish Bipolar Collection (SWEBIC) was launched to investigate the genetic basis of bipolar disorder. Here, we provide a detailed overview of the procedures and assessment tools used during the SWEBIC data collection.

Methods: The SWEBIC collection occurred in two waves, the first from 2009 to 2013, followed by the second wave from 2017 to 2022. Recruitment primarily relied on the Swedish National Quality Register for Bipolar Disorders (BipoläR). Additional sources included the Hospital Discharge Register, an online questionnaire, and identification of individuals with bipolar disorder from other cohort studies. We assessed the diagnostic validity of the BipoläR entries by reviewing randomly selected medical records from the study participants.

Results: Across the two waves, SWEBIC recruited 8580 individuals diagnosed with bipolar disorder, 89 percent from BipoläR. The bipolar disorder diagnoses in BipoläR showed high agreement with medical records (positive predictive value of 0.90). The response rate in BipoläR was higher during the first (61%) than the second wave (23%). Further, the proportion of individuals with subtype 1 was higher in the first wave. Including individuals from other cohort studies, the total number of DNA samples from individuals with bipolar disorder in SWEBIC exceeds 10,000.

Conclusions: Using quality registries to identify patients for large cohort studies facilitates genetic research with high recruitment efficiency and throughput combined with rich phenotypic data. The extensive data and biological samples collected in SWEBIC will continue to be a valuable resource for future studies, advancing our understanding of the genetic basis of bipolar disorder.