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Limitations of microscopy to differentiate Plasmodium species in a region co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi

Barber, Bridget E., William, Timothy, Grigg, Matthew J., Yeo, Tsin W. and Anstey, Nicholas M. (2013). Limitations of microscopy to differentiate Plasmodium species in a region co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi. Malaria Journal,12:1-6.

Document type: Journal Article
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Title Limitations of microscopy to differentiate Plasmodium species in a region co-endemic for Plasmodium falciparum, Plasmodium vivax and Plasmodium knowlesi
Author Barber, Bridget E.
William, Timothy
Grigg, Matthew J.
Yeo, Tsin W.
Anstey, Nicholas M.
Journal Name Malaria Journal
Publication Date 2013
Volume Number 12
ISSN 1475-2875   (check CDU catalogue open catalogue search in new window)
Scopus ID 2-s2.0-84871956766
Start Page 1
End Page 6
Total Pages 6
Place of Publication United Kingdom
Publisher BioMed Central Ltd.
HERDC Category C1 - Journal Article (DIISR)
Abstract Background
In areas co-endemic for multiple Plasmodium species, correct diagnosis is crucial for appropriate treatment and surveillance. Species misidentification by microscopy has been reported in areas co-endemic for vivax and falciparum malaria, and may be more frequent in regions where Plasmodium knowlesi also commonly occurs.

Methods
This prospective study in Sabah, Malaysia, evaluated the accuracy of routine district and referral hospital-based microscopy, and microscopy performed by an experienced research microscopist, for the diagnosis of PCR-confirmed Plasmodium falciparum, P. knowlesi, and Plasmodium vivax malaria.

Results
A total of 304 patients with PCR-confirmed Plasmodium infection were enrolled, including 130 with P. knowlesi, 122 with P. falciparum, 43 with P. vivax, one with Plasmodium malariae and eight with mixed species infections. Among patients with P. knowlesi mono-infection, routine and cross-check microscopy both identified 94 (72%) patients as “P. malariae/P. knowlesi”; 17 (13%) and 28 (22%) respectively were identified as P. falciparum, and 13 (10%) and two (1.5%) as P. vivax. Among patients with PCR-confirmed P. falciparum, routine and cross-check microscopy identified 110/122 (90%) and 112/118 (95%) patients respectively as P. falciparum, and 8/122 (6.6%) and 5/118 (4.2%) as “P. malariae/P. knowlesi”. Among those with P. vivax, 23/43 (53%) and 34/40 (85%) were correctly diagnosed by routine and cross-check microscopy respectively, while 13/43 (30%) and 3/40 (7.5%) patients were diagnosed as “P. malariae/P. knowlesi”. Four of 13 patients with PCR-confirmed P. vivax and misdiagnosed by routine microscopy as “P. malariae/P. knowlesi” were subsequently re-admitted with P. vivax malaria.

Conclusions
Microscopy does not reliably distinguish between P. falciparum, P. vivax and P. knowlesi in a region where all three species frequently occur. Misdiagnosis of P. knowlesi as both P. vivax and P. falciparum, and vice versa, is common, potentially leading to inappropriate treatment, including chloroquine therapy for P. falciparum and a lack of anti-relapse therapy for P. vivax. The limitations of microscopy in P. knowlesi-endemic areas supports the use of unified blood-stage treatment strategies for all Plasmodium species, the development of accurate rapid diagnostic tests suitable for all species, and the use of PCR-confirmation for accurate surveillance.



Keywords Plasmodium knowlesi
Malaria
Microscopy
Diagnosis
DOI http://dx.doi.org/10.1186/1475-2875-12-8   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)
Open access True
Additional Notes This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Description for Link Link to CC Attribution 2.0 License
URL http://creativecommons.org/licenses/by/2.0/au/legalcode


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