Background: Pulmonary sarcoidosis is frequently characterized by a CD4(+)/CD8(+) ratio ≥3.5 in bronchoalveolar lavage fluid (BALF), although up to 40% of the cases present a normal or even decreased ratio, pointing out its variability and limitation as a diagnostic marker for sarcoidosis. Lung lymphocytes within the bronchial epithelium, the alveolar walls, and BALF express the integrin CD103. Our aim was to compare the expression of CD103 in BALF T-lymphocytes between sarcoidosis and other interstitial lung diseases (ILD) and to evaluate its relevance as a BALF diagnostic marker for sarcoidosis.
Methods: A total of 86 patients with ILD (mean age ± standard deviation, 42.6 ± 16.6 years; 60.5% female), who underwent BALF as part of their initial diagnostic work-up, were enrolled into 2 groups: sarcoidosis (n = 41) and other ILD (n = 45). Area under the receiver operating characteristic (ROC) curve (AUC) was used to describe the performance of CD103 for sarcoidosis diagnosis.
Results: Sarcoidosis patients presented a significantly reduced CD103 expression in BALF T-lymphocytes, more pronounced in the CD4(+) subset. The BALF CD103(+)CD4(+)/CD4(+) ratio for a cutoff point of 0.45 was associated with a better diagnostic performance for sarcoidosis (AUC: 0.86 [95% confidence interval (95% CI): 0.78-0.94]; sensitivity: 81%; specificity: 78%), even for those with a CD4(+)/CD8(+) ratio <3.5 (AUC: 0.79 [95% CI: 0.64-0.93]; sensitivity: 75%; specificity: 78%).
Conclusions: Assessment of CD103 expression in BALF CD4(+) T-lymphocytes may be a reliable tool for sarcoidosis diagnosis, independently of CD4(+)/CD8(+) ratio, pointing out the relevance of evaluating the CD103(+)CD4(+)/CD4(+) ratio in the ILD diagnostic work-up.
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