The significance of blood indicators in distinguishing bipolar disorder depressive episodes from major depression in teenagers.

Purpose: There is ongoing debate about the role of blood indicators in distinguishing between bipolar disorder depressive episodes (BD-D) and major depressive disorder (MDD) in teenagers. This study aimed to assess the role of blood indicator in distinguishing BD-D from MDD in teenagers and identify potential biomarkers. Methods: We collected clinical data of BD-D and MDD teenagers from January 2022 to January 2025. To mitigate the effects of possible confounding variables, we performed the propensity score matching (PSM) analysis. After conducting univariate analysis, we performed logistic regression analysis, and ROC curve analysis on blood indicators, then nomogram prediction model was constructed using R language software. Results: A total of 275 patients were included in each group after PSM analysis. While many blood indicator were associated with by univariate analysis, logistic regression analysis identified the lymphocyte-to-HDL ratio (LHR, p<0.0001) and platelet-to-HDL ratio (PHR, p<0.0001) as predictors for BD-D. ROC curve analysis further revealed 1.3307 and 108.3806 as the critical values for separating BD-D from MDD in teenagers. Subsequently, we established nomogram-based prediction model and obtained an AUC of 0.7097 with the calibration curve showing strong consistency and decision curve analysis indicating substantial clinical utility. Conclusions: Our investigation revealed that LHR and PHR levels were correlated with BD-D and could be considered as potential biomarkers, which was confirmed by the nomogram prediction model. We also determined their threshold values to distinguish BD-D from MDD in teenagers. We should recognize that these results still necessitate further clinical validation.