Lymphocyte Profile Analysis in Lymph Node Puncture Fluid of Mediastinal Reactive Lymphadenopathy and Its Value in Differential Diagnosis with Tuberculous Lymphadenitis.

Background: Lymphocyte profile (LP) analysis in mediastinal lymph nodes for differentiating reactive lymphadenopathy (RL) from tuberculous lymphadenitis (TBLA) remains understudied.

Methods: Patients with intrathoracic lymphadenopathy undergoing endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) were enrolled. Lymph node puncture fluid (LNPF) was analyzed via flow cytometry to compare LP characteristics between TBLA and RL. Receiver operating characteristic (ROC) analysis identified optimal diagnostic cut-offs, and sensitivity, specificity, and accuracy were calculated.

Results: A total of 41 TBLA cases and 45 RL cases were included. Compared with the TBLA group, the RL group exhibited increased proportions of CD4⁺ T cells and B cells, and decreased proportions of CD8⁺ T cells, natural killer (NK) cells, and natural killer T (NKT) cells in LNPF. Among single parameters, the CD4/CD8 ratio demonstrated the highest diagnostic performance for TBLA, with sensitivity of 88.89%, specificity of 70.73%, and accuracy of 80.23%. Among three-parameter combinations, the CD4⁺ T cell, CD8⁺ T cell, and NK cell ratio combination achieved optimal diagnostic performance, with sensitivity of 80.5%, specificity of 86.7%, and accuracy of 82.6%.