Introduction. A mandatory HIV-1 antigen (HIV p24Ag) testing has been introduced in blood and blood components donors since April 2003 (with a transient period until October 2003) in the Czech Republic (CR), which supplements the previous anti-HIV-1, 2 testing. Study design and methods. 2,481 blood and blood components donors blood samples were tested by the combined assay for HIV antigen and anti-HIV-1,2 antibodies Genscreen_ Plus HIV Ag-Ab, Bio-Rad and by the antibody test Genscreen_ HIV 1/2 version 2 simultaneously at Transfusion departments of the Masaryk’s Hospital in Ústí nad Labem and the University Hospital Královské Vinohrady in Prague in the years 2001-2002. The combined test was also used for the testing of one control panel from the National Reference Laboratory for AIDS and one seroconversion panel. Results. In the tested donors samples, there were six initially reactive samples in the antibody test and nine samples in the combined test. In these groups, repeated testing revealed five and eight repeatedly reactive samples, respectively. No reactivity was confirmed as positive or indeterminate in the National Reference Laboratory for AIDS. The results of panels testing were in agreement and unambiguous. Specificity of the combined test was somewhat lower than in the antibody test (99,68% and 99,80%, respectively). Discussion and conclusion. The diagnostic window of HIV infection is supposed to be shortened by 4,4 to 7 days by p24Ag testing in comparison to anti-HIV-1,2 testing. The residual risk of HIV infection transfer by transfusion of anti-HIV-1,2-negative blood component is estimated to be 0.3 to 2.5 times for 106 samples. The detection rate of HIV p24Ag-positive anti-HIV-1,2-negative sample in blood and blood components donors is in the range of one to 3.6x106 in Germany and in the U.S.A., one to 105 in Brazil and up to 16 per 105 donations in Thailand, respectively. In view of the low HIV infection prevalence in the population in CR the detection rate of such sample is supposed to be one in 40 years with increased cost for the testing. The benefit of introducing HIV antigen testing in CR will probably be very low. The testing of HIV-1 by PCR (HIV-1 NAT) does not seem to be presently necessary.

        Key words: HIV p24 antigen, antibodies against HIV-1,2, the combined test, donors of blood and blood components