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Impact of HIV Subtype on Performance of the Limiting Antigen-Avidity Enzyme Immunoassay, the BioRad Avidity Assay, and the BED Capture Immunoassay in Rakai, Uganda

Thursday, November 07, 2013 — Poster Session II

12:00 p.m. – 2:00 p.m.

FAES Academic Center (Upper-Level Terrace)




  • A.F. Longosz
  • D Serwadda
  • F Nalugoda
  • G Kigozi
  • V Franco
  • R.H. Gray
  • T.C. Quinn
  • S.H. Eshleman
  • O Laeyendecker


Previous studies demonstrated that individuals with subtype D HIV infection who had been infected for two or more years were frequently misclassified as assay positive using cross-sectional incidence assays. Samples from 510 subjects (212 subtype A, 298 subtype D) infected for 2.2 to 14.5 years (median 5.4 years) and not virally suppressed were tested using LAg-Avidity enzyme immunoassay (LAg-Avidity EIA), BioRad Avidity assay, and BED capture enzyme immunoassay (BED-CEIA). The performance of these three assays was evaluated using various assay cutoff values. The mean LAg-Avidity EIA result was higher for subtype A than D (4.54±0.95 vs. 3.86±1.26, p <0.001); the mean BioRad Avidity assay result was higher for subtype A than D (88.9%±12.5% vs. 75.1±30.5, p <0.001); and the mean BED-CEIA result was similar for the two subtypes (2.2±1.2 OD-n for subtype A, 2.2±1.3 OD-n for subtype D, p <0.9). The frequency of misclassification was higher for individuals with subtype D infection compared to those with subtype A infection, using either the LAg-Avidity EIA with a cutoff of <2.0 OD-n or the BioRad Avidity assay with cutoffs of <40% or <80% AI. The LAg-Avidity EIA with a cutoff <1.0 OD-n had the lowest frequency of misclassification in this Ugandan population.

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