Platelet to Lymphocyte Ratio and Monocyte to Lymphocyte Ratio in Depression: A Case-Control Study

Introduction: Platelet-to-lymphocyte ratio (PLR) and monocyte-to-lymphocyte ratio (MLR) are cheap and readily available blood parameters that are markers of inflammation and bear the potential to serve as biomarkers for depression.Aims: The primary objective of this study was to compare PLR and MLR in patients of unipolar depression with healthy controls. The secondary objectives of this study were to analyze the correlation of PLR and MLR with the severity of depression at baseline and to assess the change in PLR and MLR in patients with depression after treatment.Subjects and methods: Consenting drug-free patients of unipolar depression were included as cases if they were aged > 18 years, any gender, and were free of other psychiatric disorders, substance dependence except caffeine/nicotine, major medical/hematological illness/infection, pregnancy, or lactation. Age and sex-matched healthy adults were recruited as controls with consent. All the participants were assessed at baseline, and cases were reassessed after at least six weeks of treatment.Results: The PLR was significantly higher (p-value = 0.002) among the cases (median: 124.51, IQR:63.17) than the controls (median: 99.50, IQR:47.85), at baseline before starting treatment. The area under the curve for the receiver operating characteristic curve for PLR values at baseline was 0.633. The MLR did not differ significantly between the two groups. There was no change in PLR or MLR in cases after treatment. The PLR and MLR values did not correlate with the severity of depression at baseline.Conclusion: PLR, not MLR, could be a potential trait marker for depression. Further studies are warranted