Performance evaluation of the Bio-Rad Geenius HIV 1/2 supplemental assay

J Clin Virol. 2019 Feb;111:24-28. doi: 10.1016/j.jcv.2018.12.006. Epub 2018 Dec 19.


Background: In the US, the HIV diagnostic algorithm for laboratory settings recommends the use of an HIV-1/HIV-2 differentiation supplemental assay after an initial reactive antigen/antibody (Ag/Ab) assay result. Since the discontinuation of the Multispot HIV-1/HIV-2 Rapid Test (MS), the Geenius HIV-1/2 Supplemental assay (Geenius) is the only FDA-approved supplemental differentiation test.

Objective: We compared the performance of Geenius to MS and Western Blot (WB).

Study design: The relative seroconversion plasma reactivity of Geenius and MS was assessed using a 50% cumulative frequency analysis from 17 HIV-1 seroconverters. In addition, previously characterized plasma specimens, 186 HIV-1 positive, 100 HIV-2 positive, and 93 Ag/Ab-positive/HIV-1 RNA-negative, were tested with Geenius v1.1 software. McNemar's test was used for paired comparison analysis. A subset of 48 specimens were retested with the upgraded Geenius v1.3 software.

Results: In HIV-1 seroconverters, the relative seroconversion reactivity was 2.5 and 2 days before the first positive HIV-1 WB for Geenius and MS, respectively. In HIV-1 positive samples, Geenius performed similarly to HIV-1 WB (p=0.1687) and MS (p=0.8312). In HIV-2 positive samples, Geenius underperformed compared to HIV-2 WB (p=0.0005) and MS (p=0.0012). When using the upgraded software among the HIV-1 positive and Ag/Ab-reactive/HIV-1 RNA-negative samples, gp140 reactivity decreased without affecting characterization of HIV-2 samples.

Conclusions: With HIV-1 samples, Geenius, WB and MS performance was similar as supplemental tests. The updated Geenius software reduced false gp140 reactivity, but had no impact on identifying true HIV-2 infections. Further evaluation will assess the impact of the Geenius software update on final diagnostic interpretations.

Keywords: Confirmatory tests; Geenius; HIV diagnostics; Multispot; Supplemental tests; Western blot.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • AIDS Serodiagnosis
  • Algorithms
  • Blotting, Western / methods
  • Blotting, Western / standards
  • Chromatography, Affinity / methods
  • Chromatography, Affinity / standards*
  • Cross Reactions
  • HIV Antibodies / blood
  • HIV Infections / blood
  • HIV Infections / virology*
  • HIV Seropositivity
  • HIV-1 / immunology*
  • HIV-2 / immunology*
  • Humans
  • Mass Screening / standards
  • Reagent Kits, Diagnostic / standards*
  • Sensitivity and Specificity
  • Software*


  • HIV Antibodies
  • Reagent Kits, Diagnostic