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Analytical sensitivity of four HIV combined antigen/antibody assays using the p24 WHO standard
Marcel Miedouge1, Monique Grèze, Agnès Bailly
1Laboratoire de Virologie, Institut Fédératif de Biologie de Purpan, 330 avenue de Grande Bretagne, TSA 40031, 31059 Toulouse, Cédex 9, France. miedouge.m@chu-toulouse.fr
Insights
This study evaluated HIV diagnostic assays using the international IU/ml standard. Four of five assays met the 2 IU/ml limit, showing improved sensitivity for HIV antigen detection.
Area of Science:
- Clinical diagnostics
- Virology
- Immunology
Background:
- Established Common Technical Specifications for HIV-1 p24 assays in 2009 set the lower limit of detection at 2 IU/ml.
- Fourth-generation HIV assays detecting both antigen and antibody were primarily evaluated using older pg/ml standards.
- Performance of combined HIV assays against the current IU/ml standard remains largely unknown.
Purpose of the Study:
- To assess the performance of four common combined HIV antigen/antibody assays in France.
- To evaluate these assays against the World Health Organization (WHO) standard in IU/ml.
- To compare analytical sensitivity of combined assays with the established 2 IU/ml detection limit.
Main Methods:
- Determined the analytical sensitivity of four combined HIV antigen/antibody assays (ARCHITECT, AxSYM, VIDAS DUO Quick, VIDAS DUO Ultra).
- Included one p24 assay (VIDAS HIV p24 II) in the analytical sensitivity testing.
- Utilized serial dilutions of the WHO standard (NIBSC 90/636) for all assay evaluations.
Main Results:
- Four of the five evaluated assays demonstrated a lower limit of detection below 2 IU/ml.
- ARCHITECT Combo (1.24 IU/ml), VIDAS DUO Ultra (0.66 IU/ml), VIDAS DUO Quick (0.43 IU/ml), and VIDAS p24 (0.73–1.15 IU/ml) met the criteria.
- AxSYM assay showed a lower limit of detection close to the 2 IU/ml threshold (1.94–2.25 IU/ml).
Conclusions:
- This study provides the first data on HIV combined assay sensitivity using the IU/ml WHO standard.
- Highlights the necessity for a unified international standard for accurate assay comparison.
- Recommends on-site validation of laboratory methods using this standardized approach.
Background:
The Common Technical Specifications for HIV-1 p24 assays published in 2009 fixed the lower limit of detection for obtaining C.E. approval at 2 IU/ml against the WHO standard (first international reference, code NIBSC 90/636); it was previously 50 pg/ml. Some recent fourth generation HIV assays that simultaneously detect antigen and antibody are equivalent to p24 assays, but they were mainly evaluated using p24 antigen standards in pg/ml and little is known of their performance with the IU/ml standard.
Objectives:
To evaluate four of the combined serological assays most commonly used for HIV diagnosis in France against the WHO standard in IU/ml.
Study Design:
The analytical sensitivity of four combined p24 antigen and antibody assays (ARCHITECT HIV Ag/Ab Combo, AxSYM HIV Ag/Ab Combo, VIDAS HIV DUO Quick and VIDAS HIV DUO Ultra) and of one p24 assay (VIDAS HIV p24 II) were determined using dilutions of the WHO standard.
Results:
Four of the five assays had a lower limit of detection below 2 IU/ml: 1.24 for ARCHITECT Combo, 0.66 for VIDAS DUO Ultra, 0.43 for VIDAS DUO Quick and 0.73 to 1.15 for VIDAS p24, while that of AxSYM was close to 2 (1.94-2.25).
Conclusions:
We have provided the first data on the lower limit of detection of HIV combined assays using the IU/ml WHO standard and demonstrated the need for a single international standard for comparing assays. We recommend the use of this approach in medical laboratory to validate on site their methods.
