Cholesterol crystals causing falsely elevated automated cell count.

This is a report of 3 cases of body fluid containing numerous cholesterol crystals that caused falsely elevated cell counts on an automated cell counter. Two of the cases were pleural effusion fluid from patients with long-standing rheumatoid arthritis. Fluid in the third case was from upper extremity cystic lesions of a patient with squamous cell carcinoma of the head and neck. Microscopic examination revealed abundant cholesterol crystals in all fluid samples. In all 3 cases, initially, the automated cell counter reported very elevated WBC and RBC counts that were much higher than those from the manual count. This interference by cholesterol in the automated cell counter is discussed. In addition, possible pathophysiology of cholesterol formation in the body fluid is discussed and chylous and pseudochylous (chyliform) effusions are reviewed. Finally, the use of automated instruments in the evaluation of body fluid is reviewed.