Role of the Lymphocyte Profile in Mediastinal Lymph Nodes in the Differential Diagnosis of Sarcoidosis and Tuberculous Lymphadenitis Patients Undergoing EBUS-TBNA.

Background: The value of lymphocyte profiling (LP) in mediastinal lymph nodes for the differential diagnosis of sarcoidosis has not been extensively studied, and existing literature presents mixed results.

Methods: This was a prospective study of patients with intrathoracic lymphadenopathy who underwent endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA). LP in lymph node puncture fluid (LNPF) was evaluated using flow cytometry. The results of LP in sarcoidosis patients were compared with tuberculous lymphadenitis (TBLA) patients. Receiver operating characteristic (ROC) analysis was performed to determine the optimal cut-offs of the statistically significant parameters for screening for sarcoidosis. Based on the optimal cut-offs and the final diagnosis of sarcoidosis and TBLA, the sensitivity, specificity, and accuracy of every statistically significant parameter and different combinations of the above three parameters were calculated for the diagnosis of sarcoidosis.

Results: Forty-five cases of sarcoidosis and 33 cases of TBLA were enrolled in this study. Compared with the LP in TBLA patients, in sarcoidosis patients, the proportion of CD4 T cells and CD4/CD8 ratio increased, and the proportion of CD8 T cells and natural killer (NK) cells decreased. Among all single parameters, the CD4/CD8 ratio had high diagnostic sensitivity (84.4%), specificity (81.8%), and accuracy (83.3%) for sarcoidosis. Among all the combinations of three parameters, the combination of CD4, CD8, and NKT/NK ratio had high diagnostic sensitivity (91.1%), specificity (84.8%), and accuracy (87.2%) for sarcoidosis.

Conclusions: Assessment of LP in LNPF may improve the differential diagnostic accuracy of sarcoidosis from TBLA and further strengthen the importance of LP in LNPF in the diagnostic workup of sarcoidosis.