Abnormal depolarizing patterns in three patients with filarial infection.

Several authors have described a particular potential of automated depolarization analysis in detecting malaria infection as part of the routine full blood count (FBC) performed by the Cell-Dyn 4000 analyzer. In these cases, abnormal depolarizing patterns are due to the presence of leukocyte-associated malaria hemozoin, a pigment which depolarizes the laser light. In this report we describe samples from three individual patients who did not have malaria infection but showed abnormal depolarizing events. Further investigation determined that these samples were from patients infected by the nematode Mansonella perstans. The observed depolarizing pattern consisted of a normal depolarizing eosinophil population and in addition an abnormal depolarizing population that showed a close "linear" relationship between "granularity" (90 degrees depolarization) and "lobularity" (90 degrees polarization). This atypical population was smaller than normal leukocytes and thus clearly different from the patterns associated with malaria infection. Abnormal depolarization patterns of M. perstans clearly do not reflect leukocyte-associated malaria hemozoin. It is possible however that the erythrocyte-lysing agent used to facilitate leukocyte analysis by the instrument may have caused microfilaria fragmentation and thus the distinctive "straight-line" features of the abnormal scatter plots