Immunological testing for malaria and blood donor deferral: the experience of the Ca' Granda Polyclinic Hospital in Milan.

BACKGROUND: Current European regulations require a deferral period of 6 months or 3 years, depending on the risk of exposure, for prospective blood donors at risk of malaria. This period may be reduced to 4 months if an immunological or molecular genomic test is negative at each donation, but Italian regulations have not adopted this provision. As cases of transfusion-transmitted malaria have been recorded in medical literature in blood donors deferred for 3 years and not tested, the Immunohematology and Transfusion Centre of the Ca' Grande Polyclinic Hospital in Milan decided to introduce immunological testing for all donors at risk of malaria. MATERIALS AND METHODS: Four hundred and twelve blood donors at risk of malaria, who had lived in a malarial area during the first 5 years of life or for more than 6 consecutive months, were tested for malarial antibodies using an enzyme immunoassay kit. The kit (Malaria EIA, Newmarket, UK) uses four recombinant antigens specific for P. falciparum and P. vivax and with cross-reactivity for P. ovale and P. malariae. The kit detects total immunoglobulin antibodies against P. falciparum and P. vivax and shows 80% cross-reactivity with P. ovale and 67% with P. malariae. Antibody-positive samples were further checked by an immunochromatographic test for P. falciparum, P. vivax, P. ovale and P. malariae antigens and by haemoscopy (thin film and thick smear). RESULTS: Italian citizens accounted for 16.8% (69/412) of the whole group of donors examined. We found that 8.7% of the donors who were classified as being at risk of malaria were positive for total immunoglobulin antibodies. Only one Italian citizen resulted positive for the test. The positive candidates were deferred from blood donation. None of the antibody-positive donors was confirmed positive by the immunochromatographic test and by haemoscopy. CONCLUSION: The introduction of a malarial screening test in the assessment of blood donor eligibility may increase the safety of blood donations, but could further reduce blood availability. If immunological testing were to be accepted nationally as a valid method of assessing the risk of malaria, more than 90% of the donors who are currently deferred for 3 years could be accepted 4 months after their last visit to an endemic area, thus increasing the availability of blood.