Limitations of haemozoin-based diagnosis of Plasmodium falciparum using dark-field microscopy

Malaria Journal

Research

Joshua L Proctor¹  Matthew P Horning²  Michael C Hegg²  Benjamin K Wilson²  Charles Delahunt³ 

[1] Institute for Disease Modeling, Bellevue, WA, USA;Intellectual Ventures Lab, Bellevue, WA, USA;Intellectual Ventures Lab, Bellevue, WA, USA;University of Washington, Seattle, WA, USA;

关键词: Haemozoin;    Hemozoin;    Malaria pigment;    Dark-field microscopy;    Image-processing algorithms;    Malaria diagnostics;    Early ring parasites;   

DOI  :  10.1186/1475-2875-13-147

 received in 2014-02-16, accepted in 2014-04-12,  发布年份 2014

来源: Springer

【 摘 要 】

BackgroundThe haemozoin crystal continues to be investigated extensively for its potential as a biomarker for malaria diagnostics. In order for haemozoin to be a valuable biomarker, it must be present in detectable quantities in the peripheral blood and distinguishable from false positives. Here, dark-field microscopy coupled with sophisticated image processing algorithms is used to characterize the abundance of detectable haemozoin within infected erythrocytes from field samples in order to determine the window of detection in peripheral blood.MethodsThin smears from Plasmodium falciparum-infected and uninfected patients were imaged in both dark field (DF) unstained and bright field (BF) Giemsa-stained modes. The images were co-registered such that each parasite had thumbnails in both BF and DF modes, providing an accurate map between parasites and DF objects. This map was used to find the abundance of haemozoin as a function of parasite stage through careful parasite staging and correlation with DF objects. An automated image-processing and classification algorithm classified the bright spots in the DF images as either haemozoin or non-haemozoin objects.ResultsThe algorithm distinguishes haemozoin from non-haemozoin objects in DF images with an object-level sensitivity of 95% and specificity of 97%. Ring stages older than about 6 hours begin to show detectable haemozoin, and rings between 10–16 hours reliably contain detectable haemozoin. However, DF microscopy coupled with the image-processing algorithm detect no haemozoin in rings younger than six hours.DiscussionAlthough this method demonstrates the most sensitive detection of haemozoin in field samples reported to date, it does not detect haemozoin in ring-stage parasites younger than six hours. Thus, haemozoin is a poor biomarker for field samples primarily composed of young ring-stage parasites because the crystal is not present in detectable quantities by the methods described here. Based on these results, the implications for patient-level diagnosis and recommendations for future work are discussed.

【 授权许可】

Unknown   
© Delahunt et al.; licensee BioMed Central Ltd. 2014. This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.