The current status and potential role of laboratory testing to prevent transfusion-transmitted malaria
ABSTRACT Malaria remains a rare but serious complication of transfusion because of the asymptomatic persistence of parasites in some donors. In nonendemic countries, the predominant strategy of deferral or cellular component discard from "risk" donors is effective in minimizing the incidence but is wasteful. In endemic countries where recipients are commonly immune, transfusion strategies focus on chemoprophylaxis for the donor and recipient or ensure that blood collected in highly endemic regions is not transfused to patients from areas of low endemicity. Donors implicated in transfusion-transmitted malaria are predominantly "semi-immune" with very low parasite loads. Their detection by even the most sensitive antigen or polymerase chain reaction (PCR) assays cannot be guaranteed and, in a number of cases, is unlikely because the infectious dose is estimated to be 1 to 10 parasites in a unit of blood. Retrospective analysis of implicated donors has confirmed the presence of high titer antibodies in such individuals. In regions of low immunity, serological assays offer an efficient method to identify such infectious donors. The recent development of enzyme immunoassays (EIAs) with improved sensitivity to Plasmodium falciparum and Plasmodium vivax , the predominant transfusion threats, has heightened the appeal of serological testing. Although universal serological screening in nonendemic regions is not cost-effective, targeted screening of donors identified at risk by travel-based questioning can significantly reduce wastage through reinstatement. Importantly, transfusion safety does not appear to be compromised by this approach as evidenced by the lack of a documented transmission in France between 1983 and September 2002, where such a strategy has been used since 1976. The development of automated protein microarray-based technology has the potential to further enhance antibody/antigen sensitivity; however, its application to donor screening is likely to be some years off. There is also the potential that pathogen inactivation techniques currently under development to address the bacterial contamination of blood components may also be effective against malaria parasites to make malarial testing redundant or at least reduce its cost/benefit ratio. Nonetheless, there are still significant problems to be solved in respect of validating and licensing these systems. Assuming that they are successfully marketed, their high cost may also impact their cost-effectiveness in comparison with targeted malaria testing strategies already in place in some jurisdictions.
SourceAvailable from: Alex Owusu-Ofori
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ABSTRACT: Malaria is a leading cause of mortality worldwide, rapid and accurate diagnosis is fundamental to effective management and control of malaria. New technologies have immerged to circumvent limitations of the traditional diagnostic method. This review focuses on the quality issues with current malaria diagnostics that have been developed over time. Databases including MEDLINE, PubMed and Google beta were searched for literature pertaining to malaria diagnostics published between January 1970 and March 2009. The references of the retrieved articles were hand-searched for relevant studies. Reduction of malaria morbidity and drug resistance intensity, along with its associated economic losses require urgent upgrade of the quality of parasite-based diagnostic methods. An investment in anti-malarial drug development or malaria vaccine development should be accompanied by a parallel commitment to improve diagnostic tools and their availability to people living in resource-poor malaria endemic areas.
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ABSTRACT: Background: Rapid diagnostic tests for malaria are now a commonly used procedure for malaria diagnosis. Despite some problems related to sensitivity and applicability, malaria rapid diagnostic tests (RDTs), are currently considered the best option to overcome well trained experts in blood banks and fast releas of blood units. Objectives: To detect malarial parasites using OptiMAL IT rapid test and to compare this method with the peripheral blood smear (PBS) and polymerase chain reaction (PCR) methods. Methods: Blood samples were collected from 100 patients clinically confirmed of having malaria and from 6698 random healthy blood donor volunteers. These samples were used to perform PBS examination, the OptiMAL test and PCR by standard protocols. Results: PBS examination found malarial parasites in 100 (100%) patients samples with a parasite load more than 0.01% and negative for all samples of blood donor volunteers. Positive samples obtained in PBS were also positive by OptiMAL test without differentiating between mixed infection. PCR could detect P. falciparum in 100 (100%) patients samples and two (2%) were positive for P. vivax in addition to P. falciparum. Conclusions: OptiMAL IT rapid diagnostic test can replace the peripheral blood smear method in blood banks with taking into consideration the limit of kit parasite load detectability. PCR is the most sensitive method that can detect low parasitaemia and mixed infection.