title: Incorrect identification of recent HIV infection in adults in the United States using a limiting-antigen avidity assay.
abstract: OBJECTIVE
  To evaluate factors associated with misclassification by the limiting-antigen avidity (LAg-avidity) assay among individuals with long-standing HIV infection.
  
  
  METHODS
  Samples were obtained from the Multicenter AIDS Cohort Study and AIDS Linked to the IntraVenous Experience cohort (1089 samples from 667 individuals, 595 samples collected 2-4 years and 494 samples collected 4-8 years after HIV seroconversion). Paired samples from both time points were available for 422 (63.3%) of the 667 individuals.
  
  
  METHODS
  Samples were considered to be misclassified if the LAg-avidity assay result was 1.5 or less normalized optical density (OD-n) units.
  
  
  RESULTS
  Overall, 4.8% (52/1089) of the samples were misclassified, including 1.8% [16/884, 95% confidence interval (CI) 1.09-3.06%] of samples from individuals with viral loads above 400 copies/ml and 1.4% (10/705) of samples from individuals with viral loads above 400 copies/ml and CD4 cell counts above 200 cells/μl (95% CI 0.68-2.60%). Age, race, sex, and mode of HIV acquisition were not associated with misclassification. In an adjusted analysis, viral load below 400 copies/ml [adjusted odds ratio (aOR) 3.72, 95% CI 1.61-8.57], CD4 cell count below 50 cells/μl (aOR 5.41, 95% CI 1.86-15.74), and low LAg-avidity result (≤1.5 OD-n) from the earlier time point (aOR 5.60, 95% CI 1.55-20.25) were significantly associated with misclassification.
  
  
  CONCLUSIONS
  The manufacturer of the LAg-avidity assay recommends excluding individuals from incidence surveys who are receiving antiretroviral therapy, are elite suppressors, or have AIDS (CD4 cell count <200 cells/μl). The results of this study indicate that those exclusions do not remove all sources of assay misclassification among individuals with long-standing HIV infection.
authors: aLaboratory of Immunoregulation, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH bDepartment of Epidemiology, Johns Hopkins Bloomberg School of Public Health cDepartment of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland dDepartment of Epidemiology, School of Public Health, University of California at Los Angeles, Los Angeles, California eDepartment of Medicine fDepartment of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
authors: Andrew F
authors: AF
authors: Longosz
authors: Shruti H
authors: SH
authors: Mehta
authors: Gregory D
authors: GD
authors: Kirk
authors: Joseph B
authors: JB
authors: Margolick
authors: Joelle
authors: J
authors: Brown
authors: Thomas C
authors: TC
authors: Quinn
authors: Susan H
authors: SH
authors: Eshleman
authors: Oliver
authors: O
authors: Laeyendecker
mesh_terms: D000328:Adult; D000368:Aged; D000915:Antibody Affinity; D018791:CD4 Lymphocyte Count; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D014481:United States / Q000453:epidemiology; D019562:Viral Load; D055815:Young Adult