Diagnosis by Automated Blood Analyzer
Kimberly Nadine Jones, Brett Mascia, Linda Waggoner‐Fountain, Richard D. Pearson · Clinical Infectious Diseases · 2001
Diagnosis: Acute malaria due to Plasmodium vivax. After collection of a peripheral blood sample in a tube containing dipotassium EDTA, a routine WBC count was performed by use of the Cell-Dyn 4000 automated blood-cell analyzer (Abbott). After lysis of RBCs, free malarial parasites were detected as a distinct population on the basis of light-scattering traits, which allow cells to be distinguished according to their varying nuclear and cytoplasmic optical characteristics (i.e., granularity, lobularity, complexity, and size). Specifically, the malaria organisms appeared on the scattergram (figure 1) as a population that was slightly smaller than lymphocytes, as revealed by their low angle of scatter (1°–3°), and that had greater granularity and surface complexity, as revealed by the pattern of orthogonal scatter (90°). In addition, these cells exhibited little wide-angle light scatter (3°–11°). The diagnosis of P. vivax malaria was confirmed in this case by examination of Wright-Giemsa—stained slides. A scattergram of a complete blood count sample (figure 2) from a healthy 8-year-old male is provided for comparison, to show the normal distributions of WBCs.