Immunoassay Screens Risky Malaria Blood Donations
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An enzyme-linked immunosorbent assay (ELISA) has been used to screen blood donations in an area highly endemic for malaria.
The main causative agent of malaria, Plasmodium falciparum, poses a threat on critical transfusions for road accident victims, pregnancy-related hemorrhages and child anemia enhancing the risk of transfusion-transmitted malaria (TTM).
Scientists at the University of Strasbourg (Alsace, France) collected blood in ethylenediaminetetraacetic acid (EDTA) tubes from 2,515 voluntary blood donors in Benin, over a period of 10 months, from May 2009 and March 2010. Microscopic examination was used to count parasites and parasite density (PD) was expressed as the number of parasites per µL of blood.
The plasmodium lactate dehydrogenase (pLDH) antigen detection was performed by a sandwich ELISA notably an ELISA-malaria antigen test (apDianv; Turnhout, Belgium) that detects pLDH via immunocapture. The apDia Antigen ELISA is an in vitro diagnostic immunoassay (IVD) for the qualitative determination of Plasmodium spp. Antibody screening was performed using a homemade ELISA-antibody test.
Among the 2,025 males and 488 females screened, the rate of asymptomatic Plasmodium carriage was 295/2,515 (11.7%). Males had a higher infection rate of 12.4% than did females at 8.8%. Parasite density was very low with between seven and100 parasites per µL of blood reported in 80% of donors with parasitaemia. Three malaria species were diagnosed: P. falciparum in 280/295 patients (95.0%), Plasmodium malariae in 14/295 (5.0%), and Plasmodium ovale in 1/295 (0.34%). The use of a highly sensitive assay enabled pan Plasmodium pLDH detection in 966/2,515 (38.4%) and malaria antibody prevalence was found in 1,859/2,515 (73.9%).
The authors concluded that detection of the pLDH antigen seems to be an adequate screening tool in endemic areas, for this antigen indicates parasite presence. Routine screening of all donated blood would prevent infected blood donations and reduce P. falciparum transmission in critical patients, such as children and pregnant women. This tool would also decrease medical prophylaxis in donation recipients and contribute to lower Plasmodium resistance. One drawback was that if the donors had taken self-treatment measures prior to blood donation, malaria infection was masked and pLDH detection failed.
The study was published on August 8, 2013, in the Malaria Journal.