Comparison of techniques used to screen blood donations for malaria antibodies

In France all but one of the serological tests used to screen blood donations rely on ELISA-based techniques. The exception is malaria antibody detection that is performed by the indirect fluorescent antibody technique using commercially available kits. The reagent kit used at the French Army Blood Bank (FABB) is Falciparum-Spot IF (bioMerieux). However since the antigens in this kit are obtained from group A1 red blood cell cultures, false positive results can occur due to binding of natural antiglobulins. Over a 10-month period at the FABB, we disqualified a total of 55 donations (5.02% of total donations) because of positive Falciparum-Spot IF@1000 test results. Most disqualified donations (84%) involved donations with group O red blood cells. In the present retrospective study, these 55 disqualified donations were used to compare the specificity of three other serological tests used for detection of malaria antibodies: Falciparum-SpotIF after elimination of natural antiglobulins by absorption and neutralization with Witebski reagent and Paludix (Diagast). Use of all three techniques provided a specificity gain of over 87% but elimination using Witebski reagent led to a loss of sensitivity. At the FABB we have been using the Falciparum-Spot IF kit after elimination of natural antiglobulins since April 2001. Only 1.62% of donations tested have been disqualified due to the presence of malaria antibodies including 52% with group O red blood cells.