Diagnostic Value of the CD103+CD4+/CD4+ Ratio to Differentiate Sarcoidosis from Other Causes of Lymphocytic Alveolitis.

Background: The CD103 integrin is present on CD4+ lymphocytes of the bronchial mucosa, but not on peripheral blood CD4+ lymphocytes. It has been hypothesized that CD4+ lymphocytes in pulmonary sarcoidosis originate from redistribution from the peripheral blood to the lung, and therefore do not bear the CD103 integrin. Some data suggest that a low CD103+ percentage among bronchoalveolar lavage fluid (BALF) CD4+ lymphocytes discriminates between sarcoidosis and other diagnoses.

Objective: To determine the diagnostic value of BALF CD103+ to identify sarcoidosis among other causes of alveolar lymphocytosis in a large retrospective case series.

Methods: Among 391 consecutive bronchoalveolar lavages performed at our institution and analyzed by flow cytometry, we identified 207 cases, which were grouped into nine diagnostic categories: sarcoidosis, tuberculosis, non-tuberculous infections, hypersensitivity pneumonitis, non-specific interstitial pneumonia, organizing pneumonia, drug-induced lung diseases, other interstitial lung diseases (ILDs), and other diagnoses. To assess the discriminative value of the CD103+CD4+/CD4+ ratio to distinguish sarcoidosis from other entities, areas under ROC curves (AUC) were calculated.

Results: Sarcoidosis patients (n = 53) had significantly lower CD103+CD4+/CD4+ ratios than patients in other diagnostic categories. The AUC was 62% for sarcoidosis compared to all other diagnoses, and 69% for sarcoidosis compared to other ILDs. When combining CD103+CD4+/CD4+ and CD4+/CD8+ ratios, the AUC increased to 76 and 78%, respectively. When applying previously published cut-offs to our population, the AUC varied between 54 and 73%.

Conclusions: The CD103+CD4+/CD4+ ratio does not accurately discriminate between sarcoidosis and other causes of lymphocytic alveolitis, neither alone nor in combination with the CD4+/CD8+ ratio, and is not a powerful marker for the diagnosis of sarcoidosis.