[Biological tests in sarcoidosis: contribution to diagnosis and surveillance]

No single laboratory examination is diagnostic. On the other hand, such examinations support the diagnosis and aid in management of treated patients. In the serum, there is lymphopenia with a lowered CD4/CD8 ratio. An increase in beta 2-microglobulin and in the soluble IL-2 receptor reflect T lymphocyte activation. A classic observation is hypercalcaemia with hypercalciuria. The increase in angiotensin I converting enzyme reflects the body granulomatous mass. The results of bronchoalveolar lavage show the characteristics of the alveolitis associated with granulomatosis, accumulation of CD4+ T lymphocytes and activated alveolar macrophages. In practice, biochemical anomalies are of interest in the follow-up of treated patients.