Automated malaria detection by depolarization of laser light

Abstract

Summary. Anecdotal experience with full blood count (FBC) technology incorporating analysis of depolarized laser light (DLL) for the enumeration of eosinophils showed that malaria infection generated unusual distributions in the white cell channels. The objective of this study was to identify and define criteria for a diagnosis of malaria using this technology. To determine sensitivity, specificity, and positive and negative predictive values, 224 directed samples referred specifically for malaria were used; true positives were defined as those in which malaria was identified by microscopic and/or immunological methods. For the DLL method, positive was defined as one or more large mononuclear cell(s) for which the 90Њ depolarized signal exceeded the 90Њ polarized signal. To determine possible utility in a routine haematology laboratory setting, 220 random undirected FBC samples were evaluated for possible malaria infection by the DLL method. Of the 224 directed samples, 95 were malaria positive as determined by microscopic and/or immunological methods, and 129 were negative. For the DLL method, overall sensitivity was 72% (90% in the case of Black Africans), and specificity 96%. Positive and negative predictive values overall were 93% and 82% respectively. In the utility study a single positive result was identified among the 220 samples studied. This was found to be from a patient with malaria. The detection of unexpected malaria by automated screening FBC analysis could substantially lower the mortality and morbidity from unascertained infection, especially in indigenous African peoples.

Detection of Imported Malaria with the Cell-Dyn 4000 Hematology Analyzer

“…Recent studies using automated hematology analyzers have demonstrated unexpected abnormalities in differential white blood cell plots and reticulocyte histograms from patients with malaria (1,2,4). Normal monocytes can be discriminated from monocytes that have ingested the malarial breakdown product hemozoin because of the ability of hemozoin to depolarize laser light used for routine differentiation of eosinophils (1,4). Nuclear material of intraerythrocytic malaria parasites could be discriminated by fluorescent nucleic acid dye used in routine quantification of reticulocytes.…”

“…Recently, a number of alternative diagnostic approaches have evolved, including detection of Plasmodium species DNA stained with acridine orange in a quantitative buffy coat analysis, PCR methods, and assays based on detection of circulating Plasmodium speciesspecific antigens (e.g., P. falciparum histidine-rich protein 2). Recent studies using automated hematology analyzers have demonstrated unexpected abnormalities in differential white blood cell plots and reticulocyte histograms from patients with malaria (1,2,4). Normal monocytes can be discriminated from monocytes that have ingested the malarial breakdown product hemozoin because of the ability of hemozoin to depolarize laser light used for routine differentiation of eosinophils (1,4).…”

“…In addition, full blood count and reticulocyte analyses were performed at the Department of Clinical Chemistry with EDTAanticoagulated blood on the Cell-Dyn 4000 hematology analyzer. Details of this technology have been described previously (2,4). The presence of depolarizing monocytes was defined as the presence in a lobularity-granularity plot of any depolarizing purple event situated above a separation line constructed from a line making a 22.5°angle with the x axis and a horizontal line through granularity signal channel 25 (C. S. Scott, Abbott Diagnostics, Maidenhead, Berkshire, United Kingdom, per-sonal communication) (Fig.…”

Design of Malaria Diagnostic Criteria for the Sysmex XE-2100 Hematology Analyzer

“…Hematology analyzers evaluated for malaria detection include the Cell-Dyn (Abbott Diagnostics, Santa Clara, CA), 3 the GEN.S and LH-750 (Beckman Coulter, Miami, FL), 4 and the XE-2100 and XS-1000 i (Sysmex Corporation, Kobe, Kansai, Japan). 5,6 The Sysmex XE-2100 is an automated hematology analyzer that uses flow cytometry, direct current (DC) impedanciometry, and radiofrequency conductance (RF) to detect and measure blood corpuscular elements.…”

Automated Detection of Malaria-Associated Pseudoeosinophilia and Abnormal WBC Scattergram by the Sysmex XE-2100 Hematology Analyzer: A Clinical Study with 1,801 Patients and Real-Time Quantitative PCR Analysis in Vivax Malaria-Endemic Area

“…8 In several studies, the percentage of hemozoin-containing WBCs varied according to populations, age, and disease activity. [13][14][15] A remarkable reduction in sensitivity in this study was probably caused by the presence of younger and fewer circulating parasites, severity of infection, and host immunity factors, [16][17][18] which produced less hemozoin and were below the analyzer detection limits. Our study group was larger (1,801 patients) than that of the previous study of South Korea (463 patients), 8 but further evaluation will be needed with larger samples.…”