Background: This study examines the association between the coefficient of variation(%CV) of lithium levels and episode risk and frequency in bipolar patients maintaining serum lithium levels within the therapeutic range.
Methods: We retrospectively reviewed patients with bipolar disorder under care from 2018 to 2022. Inclusion criteria were at least two years of follow-up, a minimum of three annual lithium level measurements within the therapeutic range. Patients were categorized based on seizure status. We calculated mean lithium levels, standard deviation(SD), and %CV.
Results: The study included 75 patients (patients with-without episodes, 39-36). Demographic data revealed no significant differences. While mean lithium levels showed no significant disparity between groups, SD and %CV were notably higher in the patients with episodes(p<0.05). ROC analysis demonstrated AUC values of 0.722(95%CI:0.607-0.836 p=0.001) for %CV and 0.709(95%CI:0.593-0.826;p=0.002) for SD. The optimal %CV cutoff was 17.39, with 67% sensitivity and 69% specificity. A weak correlation was found between %CV and the number of episodes (p=0.001,r=0.376). The post hoc power analysis for this study was 0.78.
Conclusions: Despite acceptable lithium levels, patients with recent episodes exhibited significant lithium level fluctuations. Integrating %CV with real-time lithium measurements during bipolar disorder follow-up may enhance clinical monitoring and seizure prediction.