Diagnostic Power of the CD4+/CD8+ Ratio and the Expression of Activation and Memory Markers in Differentiating Sarcoidosis from Tuberculosis, Idiopathic Pulmonary Fibrosis, and Other Interstitial Lung

Sarcoidosis is a complex inflammatory disease of unknown etiology affecting mostly the lungs and poses a significant diagnostic challenge, particularly in regions where tuberculosis (TB) is endemic. The diagnostic complexity intensifies due to shared clinical and radiological features between sarcoidosis and TB, as well as similarities with idiopathic pulmonary fibrosis (IPF) in cases that progress to pulmonary fibrosis. Accurately distinguishing between these diseases is critical for timely and effective patient management. This study breaks new ground by evaluating the diagnostic power of the bronchoalveolar lavage (BAL) CD4/ CD8 ratio, along with key activation and memory markers to differentiate sarcoidosis from TB, IPF, and other-interstitial lung diseases (ILDs). A cohort of 68 patients with ILDs, including sarcoidosis (n = 37), TB (n = 19), IPF (n = 6), and Other-ILDs (n = 6) were assessed. The CD4/CD8 ratio and a panel of activation and memory markers were analyzed through flow cytometry. Sarcoidosis exhibited a significantly higher CD4/CD8 ratio compared to those with TB, IPF, and Other-ILDs. An optimal cutoff value of 3.7 for the CD4/CD8 ratio in sarcoidosis with an area under the ROC curve (AUC) of 0.7%, had a specificity of 96.8%, and a sensitivity of 43.2%. In addition, a significant difference was detected in CD38, CD45RA, CD45RO, and CD62L expression. Combining the CD4/CD8 ratio (> 3.7) with the expression of CD38, CD62L, and memory markers is a promising new tool for the differential diagnosis of sarcoidosis.