A Novel Joint Index Based on Peripheral Blood CD4+/CD8+ T Cell Ratio, Albumin Level, and Monocyte Count to Determine the Severity of Major Depressive Disorder

Background: A peripheral blood laboratory test may be an easy and ideal method for determining major depressive disorder (MDD) severity, because the current depression assessment scales lack sensitivity and objectivity. This study was aimed at exploring the association between laboratory parameters and disease severity. Methods: : MDD severity in the training and validation cohorts (n = 99 and 97, respectively) was classified using the Hamilton Depression Scale. Pretreatment laboratory parameters were evaluated. Significant severity-associated factors were identified using a multivariate logistic model and combined to develop a joint index through binary logistic regression analysis. The area under the receiver operating characteristic curve (AUC) was used to evaluate the index , s discriminative performance. Results: : In the training cohort, lower CD4+/CD8+ T cell ratio, albumin level, and a higher monocyte percentage (M%) were significantly associated with severe disease (P < 0.05 for all). The index was developed using these factors and calculated as -3.959 CD4+/CD8+ T cell ratio − 0.175 albumin level + 0.522 M% + 8.739, with a sensitivity and specificity of 90% and 70%, respectively. The AUC values for the index in the training and validation cohorts were 0.850 and 0.750, respectively, indicating a good discriminative performance. Conclusion: We identified disease severity-associated laboratory parameters that could be easily evaluated—CD4+/CD8+ T cell ratio, albumin level, and M%—and developed and validated a joint index for discriminating MDD severity.