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: Essam H Ibrahim
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- "have implemented malaria antibody screening such that only individuals who are known to have been exposed to organisms causing malaria are subject to deferral of donations rather than all donors who have traveled to or lived in regions where malaria is endemic. Commercial antibody enzyme-linked immunosorbent assays (ELISAs) are currently in use in some countries like the United Kingdom, France, and Australia, and reinstatement of questionnairedeferred donors was discussed in Canada and the United States   . In these cases, blood donors are tested for antibodies directed against Plasmodium-derived antigens within several months of deferral; when the tested individuals show negative antibody results, donation is allowed. "
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.
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- "However, in a na¨ıve patient, antibody levels fall more rapidly. Reinfection or relapse leads to a secondary response with a high and rapid rise in antibody titres  . Thus, in the present study, we aim to evaluate the prevalence and the level of anti-Plasmodium spp. "
ABSTRACT: In this study, we show that 40.29% of travellers with a possible history of malaria exposure were positive for anti-Plasmodium spp. antibodies, while these individuals were negative by microscopy. The antibody test described here is useful to elucidate malaria exposure in microscopy-negative travellers from endemic countries.Journal of Parasitology Research 04/2013; 2013:247273. DOI:10.1155/2013/247273
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- "In some European countries including Denmark, Indirect Fluorescence Antibody Testing (IFAT) is used to screen donor blood. This manual method depends on maintaining consistency of examination of thin smears of P. falciparum asexual blood stages by trained microscopists making inter-laboratory standardization challenging (Seed et al., 2005b; Elghouzzi et al., 2008). Alternative enzyme immune assays (EIA) and ELISAs have been developed and some studies (Kitchen et al., 2004; Seed et al., 2005a; Doderer et al., 2007; Elghouzzi et al., 2008) found comparable diagnostic sensitivity between IFAT and EIA/ELISA whereas others (Silvie et al., 2002) did not. "
ABSTRACT: Transfusion transmitted malaria (TTM) in non-endemic countries is reduced by questioning blood donors and screening of donated blood. Conventional screening is performed by Indirect Fluorescence Antibody Test (IFAT). This method is manual and difficult to standardize. Here we study the diagnostic performance of a multiplex assay for detection of antibodies against Plasmodium falciparum in donor blood using IFAT as a comparator. A multiplex assay (MPA) containing the antigens GLURP-R0, GLURP-R2, MSP3, MSP1 hybrid and AMA1 was constructed using xMAP® technology. A discrimination index for exposure to P. falciparum malaria was calculated by comparing travelers with clinical malaria (n=52) and non-exposed blood donors (n=119). The index was evaluated on blood donors with suspected malaria exposure (n=249) and compared to the diagnostic performance of IFAT. At a specificity of 95.8 %, the MPA discrimination index exhibited a diagnostic sensitivity of 90.4 % in travelers hospitalized with malaria. Percent agreement with IFAT was 92.3 %. Screening plasma from blood donors with suspected malaria exposure, we found 4.8 % to be positive by IFAT and 5.2 % by MPA with an agreement of 93.2 %. The calculated index from the MPA exhibits similar diagnostic performance as IFAT for detection of P. falciparum malaria. Combining the antibody response against multiple antigens in a discrimination index increased the sensitivity of the MPA and reduced the readout to a single value.Journal of immunological methods 07/2012; 384(1-2):62-70. DOI:10.1016/j.jim.2012.07.009 · 2.01 Impact Factor