Laboratory Diagnosis of Malaria Conventional and Rapid Diagnostic Methods
The global control of malaria is more challenging than that of many other infectious diseases: malaria is vector borne, it is caused by 5 species of Plasmodium with different geographic distributions, infection is widespread in many regions, drug resistance is common, and the disease overlaps clinically with other infectious diseases. Therefore, malaria control programs, in addition to diagnosis and testing, must also target limiting spread of the disease through vector control. Although malaria control efforts have been successful in some regions, malaria remains one of the most important causes of death in sub-Saharan Africa, particularly in women and children.
To review the current literature regarding diagnostic methods available to detect clinical malaria, with an emphasis on comparing the strengths and limitations of each method.
Current World Health Organization malaria control report and other information, recent meta-analyses of diagnostic tests, primary literature concerning the performance characteristics of different tests, and primary literature concerning how diagnostic tests are used in daily practice.
The most commonly used method for identifying cases of malaria remains microscopic examination of peripheral blood, but there is growing use of malaria rapid diagnostic tests in many regions. One of the most important findings in the recent literature is that despite the widespread use of diagnostic tests, treatment is too often based on clinical findings rather than on results of diagnostic tests.
Available from: Hans-Peter Fuehrer
- "A study in Ethiopia reported a sensitivity that varied between 44% and 96%, and a specificity of greater than 90%
. Microscopy offers significant advantages to other methods (like RDTs), but it has its own limitations, including: detection of low parasite loads, result interpretation, mixed infections and limited usefulness in non-endemic regions due to frequently inadequate training and experience of laboratory personnel
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Malaria remains one of the leading communicable diseases in Ethiopia. Early diagnosis combined with prompt treatment is one of the main strategies for malaria prevention and control. Despite its limitation, Giemsa microscopy is still considered to be the gold standard for malaria diagnosis. This study aimed to compare the performance of Giemsa microscopy with nested polymerase chain reaction (nPCR) for the diagnosis of malaria in north-west Ethiopia.
A cross sectional study was conducted in public health facilities in North Gondar, from March 2013 to April 2013. A total number of 297 subjects with suspected malaria were enrolled in the study. Finger-prick blood samples were collected and examined for Plasmodium parasites using Giemsa microscopy and standard nPCR.
Among the study participants, 61.6% (183/297) patients tested positive for malaria by Giemsa microscopy of which, 72.1% (132/183) and 27.9% (51/183) were diagnosed as Plasmodium falciparum and Plasmodium vivax, respectively. By nPCR, 73.1% (217/297) were malaria-positive. Among microscopy-negative samples, 13.1% (39/297) samples turned malaria-positive in nPCR. In nPCR, the rate of mixed Plasmodium infections was 4.7% (14/297) and 3.03% (9/297) were positive for Plasmodium ovale. Using nPCR as reference the sensitivity, specificity, positive predictive and negative predictive values of Giemsa microscopy were 82.0%, 93.8%, 97.3% and 65.8%, respectively, with a good agreement (κ = 0.668) to nested PCR. The sensitivity and specificity of Giemsa microscopy in identifyingP. falciparium infections were 74.0% and 87.4% and 63.2% and 96.5% for P. vivax infections, respectively.
Although Giemsa microscopy remains the gold standard for malaria diagnosis in resource-limited environments, its sensitivity and specificity as compared to nPCR is limited suggesting exploration of novel rapid and simplified molecular techniques for malaria-endemic countries. A high rate of misclassification and misidentification highlights the importance of adequate training for staff involved in malaria diagnosis.
Available from: Joel Mouatcho
- "Various techniques are available for malaria diagnosis. Patients presenting with a febrile illness in endemic areas are likely to be diagnosed with malaria (Wilson, 2013). Microscopy has been in use for over 100 years and is inexpensive, rapid and relatively sensitive when used appropriately (Laveran, 1891). "
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ABSTRACT: In the last decade, there has been an upsurge of interest in developing malaria rapid diagnostic test (RDT) kits for the detection of Plasmodium species. Three antigens - Plasmodium falciparum histidine-rich protein 2 (PfHRP2), plasmodial aldolase and plasmodial lactate dehydrogenase (pLDH) - are currently used for RDTs. Tests targeting HRP2 contribute to more than 90 % of the malaria RDTs in current use. However, the specificities, sensitivities, numbers of false positives, numbers of false negatives and temperature tolerances of these tests vary considerably, illustrating the difficulties and challenges facing current RDTs. This paper describes recent developments in malaria RDTs, reviewing RDTs detecting PfHRP2, pLDH and plasmodial aldolase. The difficulties associated with RDTs, such as genetic variability in the Pfhrp2 gene and the persistence of antigens in the bloodstream following the elimination of parasites, are discussed. The prospect of overcoming the problems associated with current RDTs with a new generation of alternative malaria antigen targets is also described.
Available from: omicsonline.com
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