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

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

METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.