• bipolar disorder
• clinical chemical markers
• neutrophils
• peripheral biomarkers
• platelets

Introduction: several chemical clinical inflammatory markers such as neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), lymphocyte-monocyte ratio (LMR), have recently been investigated as inexpensive and reproducible markers of systemic inflammation in many diseases. However, few studies evaluate clinical and prognostic value of NLR and PLR in psychiatric patients. The objective of this study is to investigate the clinical repercussions of eleven inflammatory markers in patients with bipolar disorder (BD).
Methods and Material: in this retrospective study, all patients between aged 18 to 65 years who were hospitalized with a diagnosis of Bipolar Disorder at the Psychiatric Clinic, Department of Clinical and Experimental Medicine, at the University of Pisa between 1 June 2019, and 1 June 2020, were evaluated for eligibility for inclusion. Those patients with complete blood counts performed within 24 h after hospitalization were included. Patients receiving any anti-inflammatory treatment or with systemic inflammatory disease capable of causing abnormal inflammatory parameters were excluded from the study. Patient records were screened retrospectively. White blood cell, neutrophil, lymphocyte, platelet, and monocyte counts were recorded retrospectively from complete blood count data collected during hospital stays, and NLR, PLR, MLR, LRR, NRR, MRR, PRR, LMR, dNLR, SIRI and AISI values were calculated from these. Sociodemographic data and clinical features of bipolar disorder were also retrieved from patient records
Results: fifty-four patients aged 18–65 were finally included in the study. NLR, dNLR, NRR, SIRI and AISI were higher in Manic / Hypomanic patients compared to depressed and euthymics. LRR values were lower in manics / hypomanics. Within the manic / hypomanic group, NLR, dNLR, NRR were higher in BD I patients. Patients with psychotic features had higher dNLR, NRR and SIRI. AISI and PRR were higher in patients with mixed symptoms. Patients with hyperthymic personality had higher NLR, dNLR, NRR, AISI, SIRI, PLR and lower LRR value compared to the rest of the sample. Compared to dysthymics they had also PRR. Dysthymic patients presented lower levels of NLR, dNLR, NRR compared to irritable and lower NLR, dNLR, NRR, PLR, PRR compared to cyclothymic. LRR and duration of illness had inverse linear correlation.
Conclusion: this study suggested the importance of a simple blood count, an inexpensive
and reproducible exam, in evaluating the etiology and course of the BD. The study indicates that some variables could be considered as both state markers for the polarity episode and trait markers for BD patients with hyperthymic personality traits. At the same, it could useful to better understand the complex relationship between inflammatory and cardiovascular disease and bipolar disorder; thus, to provide clinical implications in terms of management and treatment. Further studies must be performed to confirm these results.