Ciliocytophthoria in clinical virology

Direct immunofluorescence assays (DFAs) are used in the clinical virology l aboratory for the rapid detection of viruses. An assessment of the cellular ity of specimens submitted for DFA is necessary for the most effective use of this assay. This assessment ensures that an adequate number of the appro priate cells are present for examination. During this assessment, clinical virologists may encounter unfamiliar cellular elements or cellular fragment s. One of these elements, ciliocytophthoria, has been misinterpreted as a p arasite in specimens submitted for cytologic testing. We describe a similar case in which a technologist thought that ciliocytophthoria possibly repre sented a ciliated parasite in a nasopharyngeal specimen sent for respirator y syncytial virus DFA. After a thorough morphologic examination, the staff dismissed the possibility of a ciliated parasite. We confirmed this entity as ciliocytophthoria using morphologic criteria and the Diff-Quik stain. Th is near misidentification of ciliocytophthoria as a ciliated parasite affor ds us the opportunity to raise the awareness of clinical virologists about ciliocytophthoria. Additionally, we briefly review useful features for diff erentiating ciliocytophthoria from the only ciliate parasitic for humans, B alantidium coli. Finally, we present the utility of a commonly used cytolog ic stain, the Diff-Quik stain, for the confirmation of ciliocytophthoria.