Objective: Systemic inflammation is a factor in the pathophysiology of bipolar disorder (BD). Pan-immune inflammation value (PIV) and systemic immune-inflammation index (SII) have recently been investigated as new inflammatory markers. The aim of this study was to investigate and compare the PIV and SII as inflammation biomarkers in different mood episodes in BD and healthy controls (HC).
Methods: In this retrospective study, the parameters (white blood cells, neutrophil, monocyte, lymphocyte, and platelet counts) of 339 BD patients (138 manic, 100 depressive and 101 euthymic patients) along with 117 HC were evaluated. The PIV and the SII were calculated using these parameters and compared between the groups.
Results: PIV (p<0.001), SII (p=0.002), neutrophil (p<0.001) and monocyte (p<0.001) counts were significantly higher in the manic group than in the HC. A comparison of the HC with the depressed and euthymic groups indicated no significant difference in PIV (p=0.086, p=0.139, respectively) and SII (p=0.555, p=0.244, respectively), while neutrophil (p=0.043, p=0.042, respectively) and monocyte (p=0.01, p=0.023, respectively) counts were significantly higher in the depressed and euthymic groups. Compared to the depressed and euthymic patients, the manic patients had significantly higher PIV (p<0.001, p<0.001 respectively) and SII (p=0.019, p=0.034, respectively). PIV could to be predictive in distinguishing manic episode patients from the other groups.
Conclusion: Our findings highlight the role of the low-grade systemic inflammation in the pathophysiology of BD, particularly during the manic episode, and suggest that PIV could serve as an inflammation marker to distinguish the manic episode of BD from other phases.