A smear of leukocytes from the buffy-coat layer was obtained when peripheral blood specimens were taken for culture. Fourteen of 135 blood cultures were positive, and five of the 14, from three patients, showed Gram-positive intracellular organisms on Gram stain of the buffy-coat layer. Grampositive cocci were seen in two of three patients with staphylococcal bacteremia and Gram-positive rods in one patient with Clostridium perfringens bacteremia. These two cases illustrate the diagnostic role of the buffy-coat smear and its use in the early diagnosis of bacteremia.
Brooks GF, Pribble AH, Beaty HN. Early Diagnosis of Bacteremia by Buffy-Coat Examinations. Arch Intern Med. 1973;132(5):673-675. doi:10.1001/archinte.1973.03650110029006