Novel Immunoassay Suitable for Blood Donor Screening

A novel immunoassay can be used effectively to detect HIV contamination in blood products, according to researchers in Luxembourg. The Cobas Core HIV Combi enzyme immunoassay (EIA) is more accurate for blood donor testing than other fourth-generation screens.

According to the researchers, "Fourth-generation assays for the simultaneous detection of human immunodeficiency virus (HIV) antigen and antibody that were available on the international market until now have antigen detection modules with relatively poor sensitivity and produce a higher rate of false-positive results than third-generation enzyme immunoassays (EIAs)."

Bernard Weber and colleagues at Reunis Kutter-Lieners-Hastert Laboratories in Junglinster, Luxembourg, and other institutions in Europe and Thailand, assessed the novel test and found HIV Combi's enhanced p24 antigen detection makes the test superior in sensitivity and specificity compared with other third- and fourth-generation screens.

Using a wide range of test specimens, including serum samples from patients in various stages of infection, diluted supernatants from infected cell cultures, and more than 1,200 potentially confounding samples, data showed that the HIV Combi performance was similar to that of the dedicated p24 assays. In addition, unselected samples from blood donors were screened with the HIV Combi and other assays, the authors noted. The HIV Combi had a specificity of 99.85 percent when used to test donated blood, with only 30 consistently false positives out of more than 10,000 samples.

While not as fast as HIV reverse transcription-polymerase chain reaction screens, the HIV Combi produced results up to 6 days faster than third-generation EIAs. The report, "Multicenter Evaluation Of A New Automated Fourth-Generation Human Immunodeficiency Virus Screening Assay With A Sensitive Antigen Detection Module And High Specificity," is published in the Journal of Clinical Microbiology (2002;40(6):1938-1946).

"Our results show that a fourth-generation assay with improved specificity such as Cobas Core HIV Combi EIA is suitable for blood donor screening," Weber and colleagues concluded, "because of its low number of false positives and because it detects HIV p24 antigen with a sensitivity comparable to that of single-antigen assays."

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