TechniquesAutomated Malaria Diagnosis Using Pigment Detection
Section snippets
Automated detection of haemozoin
A new generation of automated analysers that incorporate flow-cytometric principles are currently employed in many haematology laboratories for routine FBCs. These might provide a novel way to diagnose malaria by automated detection of haemozoin during routine FBC analysis. The anisotropic properties of haemozoin have been known since the turn of the 20th century, and several microscopic methods were developed to exploit them for diagnosis 13., 14., 15.. As far back as 1945, a review
Application
Initial reports of the use of this technique in the field are promising 18., 19.. A study from South Africa 18, investigating 224 samples for which clinicians requested a malaria diagnosis test, found an overall sensitivity of 72% and specificity of 96%. In Portugal, in a series of 170 samples, a sensitivity of 95% was observed and the abnormal changes in the lobularity–granularity plots typical for malaria were not seen in several thousand FBC results obtained over several weeks (T. Hänscheid,
Value
One advantage of this method is its potential to detect cases where clinical suspicion does not lead to a request for a malaria test 19. Laboratory personnel could perform confirmatory microscopy on those samples with abnormal plots, even in the absence of a clinician's request. During a period of only 2 weeks, three cases of malaria, which were missed at presentation, were subsequently diagnosed solely on the basis of instrument scattergrams 19. The importance of this approach is highlighted
Limitations
Of concern is the number of false positives with the FBC analyser, due to persisting haemozoin-containing WBCs in the circulation 21., 22.. This problem, similar to the one observed with Histidin Rich Protein II dipstick tests because of persistent circulating antigen 3, might limit the usefulness in areas with high reinfection rates or subclinical parasitaemias. A relationship between parasitaemia and the changes detected with the instrument (‘number of purple dots’: Fig. 1) was not observed 18
Other malaria diagnostic methods
Clearly, conventional microscopy remains integral to the characterization of Plasmodium spp and the assessment of the degree of parasitaemia. Most diagnostic methods are still regarded as complements to conventional microscopy rather than as substitutes 1. Antigen detection by dipstick tests is easy and may be the solution for remote areas without laboratory access. Nonetheless, they detect only P. falciparum (and some P. vivax 4) and their sensitivities may drop significantly with low
Future directions
Although the potential usefulness of malaria diagnosis by pigment detection is clear, several aspects of this new technique need to be addressed: (1) further studies will have to confirm its sensitivity in various populations and clinical settings, given the different kinetics of haemozoin-containing WBCs 21; (2) the instrument should include an ‘alarm’ to flag suspicious samples, obviating the need to examine the scattergrams at the monitor for the malaria-typic changes; (3) a ‘re’-analysis
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Cited by (48)
Evaluation of the LH780 hematology analyzer for detection and therapeutic monitoring of malaria: Cross-reactivity with nucleated RBCs
2016, Acta TropicaCitation Excerpt :Various diagnostic methods are used to identify malarial infection; however, a rapid and convenient automated detection system is needed to improve the limitations of diagnosis (Dyer et al., 2016; Moody, 2002). Previously, various automated hematology analyzers were reported to be able to detect malaria (Campuzano-Zuluaga et al., 2010a,b; Grobusch et al., 2003; Hanscheid et al., 2000a,b; Kramer et al., 2001; Shapiro and Greenfield, 1987; Suh et al., 2003). Coulter hematology analyzers apply Coulter impedance and volume-conductance-scatter (VCS) technology for white blood cell count and differential analysis.
The hemozoin conundrum: Is malaria pigment immune-activating, inhibiting, or simply a bystander?
2013, Trends in ParasitologyMethodology and application of flow cytometry for investigation of human malaria parasites
2011, Journal of Immunological MethodsCitation Excerpt :Therefore, one can observe the presence of this substance via microscopy even in the absence of Giemsa stain (Lawrence and Olson, 1986). Several papers have used Cell Dyn cytometers (Hanscheid et al., 2000a,b; Grobusch et al., 2003) to detect the presence of hemozoin crystals as an indication of a malaria infection. Thus far this method has had sensitivity issues which can be lower than 50% (Grobusch et al., 2003).
Automated detection of haemozoin-containing monocytes for the diagnosis of malaria in microscopically negative cases during pregnancy
2009, Acta TropicaCitation Excerpt :However, they continue to liberate Hz, which is ingested by local, and likely, circulating phagocytic cells. One automated flow cytometric haematology analyser series (Cell-Dyn®, Abbott, Santa Clara, California) has the capacity to detect Hz-containing leukocytes during routine full blood count (FBC) analysis (Hänscheid et al., 2000). One such analyser was used in Lambaréné, Gabon, to generate routine FBCs from children and pregnant woman participating in various clinical studies.
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