Lymphocyte changes in secondary dengue fever: use of the Technicon H*1 to monitor progress of infection.

Secondary dengue fever as dengue hemorrhagic fever or dengue shock syndrome is a potentially fatal complication of an infection that presents with few clinical signs that help in the diagnosis. Previous workers have reported the value of buffy coat determinations of atypical lymphocytes as an aid to the diagnosis. We report here the use of an automated white blood cell differential counter, the Technicon H*1 in the monitoring of the atypical lymphocyte count as a measure of the progress of the infection in a retrospective study of serial full blood counts in 45 serologically confirmed patients. Technicon H*1 'basophil' and large unstained cell counts and manual atypical lymphocyte counts rose in tandem with the drop in platelets and decreased when the platelets recovered. In a sub-study, the atypical lymphocytes were immunophenotyped and found to be predominantly derived from T lymphocytes. We conclude that the Technicon H*1 is a useful monitor of the activity of the infection in dengue hemorrhagic fever.