שאלה חשובה

Comparison of the Abbott HIV Ag/Ab Combo and the HIV1/2 Axsym gO assays.

Janse van Rensburg E, Lotter S, Wilsdorf L, Robson B, Canosci A; International Conference on AIDS (15th : 2004 : Bangkok, Thailand).

Int Conf AIDS. 2004 Jul 11-16; 15: abstract no. B10462.
University of Stellenbosch and National Health Laboratory Service , Tygerberg, South Africa

Background: Comparison of the performance of the Abbott HIV Ag/Ab Combo (Combo) assay that detects both HIV antibodies and p24 antigen to the Abbott Axsym HIV 1/2 gO (gO) assay that only detects HIV antibodies, in a public hospital setting in Cape Town, South Africa. Methods: The following samples were tested: 300 routine samples, 200 previously tested antibody positive samples and 21 antigen positive samples. All samples were tested in parallel on the Combo and Axsym gO assays and positives were confirmed on a second antibody assay (Vironostika) or if negative on the Murex p24 antigen assay. For discrepant results a qualitative HIV PCR was done. Results: Ninety of the 300 routine samples tested were gO positive while 92 were positive on the Combo. Of the 2 Combo-positive and Ab-negative samples, one was p24Ag negative and one was p24Ag positive. The PCR result for the p24Ag negative sample was also negative. Of the 210 Ab-negative routine samples the Murex p24 test detected two additional samples positive that was negative on the Combo assay. All 200 previously Ab-positive samples were also Combo-positive. Of the 21 samples previously tested p24 antigen positive samples: a) 15 were Ab-negative and 6 were Ab-positive (gO assay) b) 17 tested Combo-positive and 4 tested Combo-negative c) of the 17 Combo-pos samples, 16 tested p24 antigen (Murex) pos and one tested p24 negative on the Murex assay d) the p24 negative sample tested positive on PCR e) of the 4 Combo-negative samples, all 4 tested positive on the p24 antigen test (Murex). The sensitivities of the Combo and the gO assays were 98.09% and 94.27% respectively, while the specificities were 99.52% and 100%. Conclusions: The added ability to detect p24 antigen did not decrease the ability of the Combo assay to detect HIV-1 antibodies. In a routine diagnostic setting, the Combo assay performed superior to the antibody only assay by being able to detect virus in the seroconversion phase of the infection.