Related Experiment Video
Updated: May 17, 2026
Comprehensive & Cost Effective Laboratory Monitoring of HIV/AIDS: an African Role Model
Published on: October 31, 2010
Performance of a fourth-generation HIV screening assay and an alternative HIV diagnostic testing algorithm
Muazzam Nasrullah1, Laura G Wesolowski, William A Meyer
1Division of HIV/AIDS Prevention, National Center for HIV, Hepatitis, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA, USA. snasrullah@cdc.gov
Objective:
We evaluated the performance of the GS fourth-generation antigen/antibody assay and compared Centers for Disease Control and Prevention's (CDC's) proposed alternative algorithm [repeatedly reactive fourth-generation immunoassay followed by an HIV-1/HIV-2 differentiation immunoassay and, if needed, nucleic acid test (NAT)] with the current algorithm (repeatedly reactive third-generation immunoassay followed by HIV-1 western blot).
Design:
A convenience sample of the following four specimen sets was acquired: 10 014 from insurance applicants, 493 known western blot-positive, 20 known western blot-indeterminate specimens, and 230 specimens from 26 HIV-1 seroconverters.
Methods:
Specimens were tested with the GS third-generation and fourth-generation immunoassays, the Multispot HIV-1/HIV-2 differentiation immunoassay, NAT, and western blot. We applied the two algorithms using these results.
Results:
Among insurance specimens, 13 (0.13%) specimens were immunoassay repeatedly reactive: two were HIV-positive (repeatedly reactive by third-generation and fourth-generation immunoassays, and western blot and Multispot positive); two third-generation repeatedly reactive and nine fourth-generation repeatedly reactive specimens were false-positive. Third-generation and fourth-generation specificities were 99.98% [95% confidence interval (CI) 99.93-100%] and 99.91% (95% CI 99.84-99.96%), respectively.All HIV-1 western blot-positive specimens were repeatedly reactive by third-generation and fourth-generation immunoassays. By Multispot, 491 (99.6%) were HIV-1-positive and two (0.4%) were HIV-2-positive.Only eight (40%) western blot-indeterminate specimens were fourth-generation repeatedly reactive: six were Multispot and NAT-negative and two were Multispot HIV-1-positive but NAT-negative.The alternative algorithm correctly classified as positive 102 seroconverter specimens with the third-generation immunoassay and 130 with the fourth-generation immunoassay compared with 56 using the western blot with either immunoassay.
Conclusion:
The alternative testing algorithm improved early infection sensitivity and identified HIV-2 infections. Two potential false-positive algorithm results occurred with western blot-indeterminate specimens.
