CD4 and sarcoidosis: However, microscopy of BALF cells (1) requires local expertise and experience in the microscopic analysis of BALF; (2) relies on the analysis of a small fraction of all BALF cells (typically 400-500 cells are counted15); and (3) cannot be combined with flow cytometric analyses of lymphocyte surface markers (eg, CD4 and CD8 in patients with suspected sarcoidosis).16