Background: Microscopy is currently the gold standard to differentiate BAL fluid (BALF) leukocytes. However, local expertise for microscopic BALF leukocyte differentiation is often unavailable in clinical practice.
Research Question: Can automated flow cytometry be used instead of microscopy to differentiate BALF leukocytes?
Study Design And Methods: A new automated flow cytometric method for BALF leukocyte differentiation, using four antibodies (anti-CD45, anti-CD66b, anti-HLA-DR, anti-CD52) given to human BALF in one tube, was developed and prospectively validated in 745 unselected subsequent BALF samples from patients with interstitial lung diseases (455 patients), infectious diseases (196 patients), and other diseases (94 patients).