Abnormal leukocyte histogram with a factitious automated white cell count due to Plasmodium vivax parasitemia--a case report.

Automated hematology analyzers are designed to produce accurate and precise blood counts on specimens which are either normal or show only numerical abnormalities. However they alert the operator in samples with unusual characteristics which could result in inaccurate measurement or require review of the blood smear. Even the most sophisticated instruments cannot recognize all the significant abnormalities that can be recognized by a human observer. Spurious automated white cell counts could result from platelet aggregates, nucleated red cells, non lysis of cells and a variety of other causes. We present a case with spurious leukocytosis due to Plasmodium vivax parasitemia which was flagged by the automated analyzer.