[Predictive value of single and combined indexes in the diagnosis of sarcoidosis]

To evaluate the predictive value of single and combined indexes in the diagnosis of sarcoidosis.

Eighty-eight patients suspected of having sarcoidosis were retrospectively investigated. The diagnostic predictive value of lymphocyte percentage and CD4/CD8 ratio in bronchoalveolar lavage (BAL), angiotensin converting enzyme (ACE) and their combination was evaluated by ROC curve method and Bayes' rule.

Final diagnosis of sarcoidosis by biopsy was available in 59 patients (67%), 16 were males (27%), 43 were females (73%), with a mean age of (48 +/- 10) years. The diagnosis of non-sarcoidosis was available in 29 patients (33%), 12 were males (41%), 17 were females (59%), with a mean age of (49 +/- 13) years. The ROC curve area of lymphocyte percentage, CD4/CD8 ratio and ACE were 0.64, 0.74 and 0.69 respectively; CD4/CD8 ratio had the best diagnostic efficiency. The optimized cut-offs of the three single indexes, lymphocyte percentage > or = 30%, CD4/CD8 ratio > or = 4.0 and ACE > or = 40 U/L, were determined by the tangential points and coordinates of the ROC curve. The positive predictive values were 76.7%, 80.4% and 76.8% respectively; CD4/CD8 ratio had the best predictive value. The ROC curve area of the combined CD4/CD8 ratio and ACE was 0.81, and the combination of lymphocyte percentage, CD4/CD8 ratio and ACE was 0.78. They were both higher than those of the respective single indexes. The combination of CD4/CD8 ratio and ACE had the best diagnostic efficiency. On the other hand, it had the best positive predictive value of 90.5% in all the diagnostic indexes.

CD4/CD8 ratio in BAL is still a useful index in the auxiliary diagnosis of sarcoidosis. The combination of CD4/CD8 ratio and ACE can improve the diagnostic efficiency and predictive value of sarcoidosis.