Inflammatory biomarkers are reportedly increased in depressed patients. Several studies have been conducted using neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and monocyte/lymphocyte ratio (MLR). The objective of this systematic review was to study the relationship between these peripheral biomarkers and suicidality in depressed patients with/without suicidal behavior, including suicide attempts and ideation, and healthy controls.

We searched the following relevant terms in the PubMed, Web of Science, and Scopus databases published in the last 5 years. We assessed the methodological quality of included studies using the Oxford criteria and reviewed the evidence following PRISMA guidelines.

Eleven studies were retained for the data synthesis, with a total sample of 1,701 participants, of which the majority (819) were patients with depression and suicidal behavior, 494 were depressed patients without suicidal behavior, and only 388 were healthy participants. Our results reinforce the idea that NLR could be an attractive, convenient, and cost-effective trait marker of suicidal vulnerability in patients with major depressive disorder (MDD).

Future large-scale replication studies are needed to examine the apparently understudied role of PLR and MLR in depressed patients in greater depth.

Correlations between neutrophil/lymphocyte, platelet/lymphocyte, and monocyte/lymphocyte ratios (NLR, PLR, and MLR, respectively) and psychopathological and clinical variables in the context of mood disorders are increasingly emerging in international scientific literature, being the former one of the most studied. The estimation of suicidal risk associated to affective disorders could benefit from such rapidly and easily available biomarker of inflammation, if significant in this regard.

The present review would like to focus on any existing correlations between NLR and suicidal risk in patients with mood disorders.

We sourced articles on the topic found in major scientific literature databases, combining the keywords “neutrophil/lymphocyte ratio”, “NLR”, “mood disorders”, “major depressive disorder”, “bipolar disorder” and “suicide risk”.

There are congruent findings of significantly higher NLR values in depressed patients attempting suicide than in depressed patients with no suicidal behaviors or healthy controls. In addition, violent means appear typical in this subgroup of depressed suicidal patients, suggesting that patients with higher levels of NLR are at risk of attempting suicide and to be successful in self-harming. Similar results have been found in patients with bipolar disorder, showing a positive correlation between NRL and suicide risk, evaluated by the Suicide Behaviors Questionnaire-Revised (SBQ-R). Moreover, in patients with a positive family history for suicide attempts, NRL was found to be a significant positive predictor of suicide risk.

These findings, although limited, support the notion that NLR might be a useful marker for suicide vulnerability in both BD and MDD patients.

No significant relationships.

Congenital heart diseases (CHD) are the most common causes of birth defects that have increased the risk of infections. Neonatal sepsis is a life-threatening condition and early diagnosis can be life-saving. We aimed to evaluate the potential role of the systemic immune-inflammatory index in the early diagnosis of neonatal sepsis.

A retrospective cohort study was conducted on 166 newborns with a diagnosis of neonatal sepsis who were admitted to our hospital with CHD between January 2017 and June 2021. Haematological indices including neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, and systemic immune-inflammatory index were calculated for all patients at the time of diagnosis of neonatal sepsis (sepsis). The sepsis values of these indices were compared with the admission values (pre-sepsis) of the patients.

The mean gestational age and birth weight of the patients were 38.36 ± 1.42 weeks and 3057.75 ± 484.68 g. It was found that absolute neutrophil count, systemic immune-inflammatory index, neutrophil/lymphocyte ratio, but not platelet/lymphocyte ratio were significantly increased at the time of sepsis. The receiver operating characteristic curve showed that systemic immune-inflammatory index, neutrophil/lymphocyte ratio, and absolute neutrophil count have predictive ability to define neonatal sepsis among newborns with CHD. The systemic immune-inflammatory index produced an area under the curve receiver operating characteristic curve of 0.76 (70% sensitivity, 70.5% specificity). To discriminate neonatal sepsis, the cut-off values of systemic immune-inflammatory index, neutrophil/lymphocyte ratio, and absolute neutrophil count were 517.19, 2.62, and 9210/mm3, respectively.

As an easily accessible and reliable indicator, systemic immune-inflammatory index may be used in combination with the other parameters in the early diagnosis of neonatal sepsis.