MEASUREMENT OF RESIDUAL LEUKOCYTES IN PLATELET CONCENTRATE UNITS

Leukocyte contamination of various blood products is implicated in feb rile transfusion reactions, in alloimmunization phenomena immunosuppre ssion, and in the transmission of viral infections. The biggest diffic ulty in interpreting published reports lies in the methods used to qua ntify residual leukocytes. As automated cell counters are not precise and sensitive enough to detect low cell counts, we compared two techni ques: i) the classical method using the Nageotte haemocytometer; and i i) fluorescent staining with propidium iodide (PI). We performed these two techniques to evaluate the residual white cell count in 41 platel et units collected by cytapheresis. The difference in results obtained with the two techniques was borderline significant (P = 0.05). To eva luate the accuracy of both techniques, we added a known number of lymp hocytes to platelet concentrates that had been filtered three times. T here was a good correlation between the values obtained using the two techniques (r > 0.99). However, though the difference between the know n value and PI results was not significant, the difference for Nageott e cell counter results was significant (P < 0.0001). From a practical point of view, the PI fluorescent technique is simple, rapid, and easy to carry out. Our results demonstrate the reliability of the PI techn ique for the evaluation of residual leukocytes.