title: Comparison of cross-sectional HIV incidence assay results from dried blood spots and plasma.
abstract: BACKGROUND
  Assays have been developed for cross-sectional HIV incidence estimation using plasma samples. Large scale surveillance programs are planned using dried blood spot (DBS) specimens for incidence assessment. However, limited information exists on the performance of HIV cross-sectional incidence assays using DBS.
  
  
  METHODS
  The assays evaluated were: Maxim HIV-1 Limiting Antigen Avidity EIA (LAg-Avidity), Sedia HIV-1 BED-Capture EIA (BED-CEIA), and CDC modified BioRad HIV-1/2 Plus O Avidity-based Assay (CDC-BioRad Avidity) using pre-determined cutoff values. 100 matched HIV-1 positive plasma and DBS samples, with known duration of infection, from the Consortium for the Evaluation and Performance of HIV Incidence Assays repository were tested. All assays were run in duplicate. To examine the degree of variability within and between results for each sample type, both categorical and continuous results were analyzed. Associations were assessed with Bland Altman, R2 values and Cohen's kappa coefficient (ĸ).
  
  
  RESULTS
  Intra-assay variability using the same sample type was similar for all assays (R2 0.96 to 1.00). The R2 values comparing DBS and plasma results for LAg-Avidity, BED-CEIA, and CDC-BioRad Avidity were 0.96, 0.94, and 0.84, respectively. The concordance and ĸ values between DBS and plasma for all three assays were >87% and >0.64, respectively. The Bland-Altman analysis showed significant differences between plasma and DBS samples. For all three assays, a higher number of samples were classified as recent infections using DBS samples.
  
  
  CONCLUSIONS
  DBS and plasma sample results were highly correlated. However, when compared to plasma, each assay performed somewhat differently in DBS at the lower and higher ends of the dynamic range. DBS samples were more likely to be classified as recently infected by all three assays, which may lead to overestimation of incidence in surveys using performance criteria derived for plasma samples.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Katherine E
authors.initials: KE
authors.lastname: Schlusser
authors.affiliation: Department of Medicine, School of Medicine, University of California at San Francisco, San Francisco, CA, United States of America.
authors.forename: Christopher
authors.initials: C
authors.lastname: Pilcher
authors.affiliation: University of São Paulo, São Paulo, Brazil.
authors.forename: Esper G
authors.initials: EG
authors.lastname: Kallas
authors.affiliation: Grupo Hospitalar Conceicao, Porto Alegre, Brazil.
authors.forename: Breno R
authors.initials: BR
authors.lastname: Santos
authors.affiliation: Department of Medicine, School of Medicine, University of California at San Francisco, San Francisco, CA, United States of America.
authors.forename: Steven G
authors.initials: SG
authors.lastname: Deeks
authors.affiliation: Department of Medicine, School of Medicine, University of California at San Francisco, San Francisco, CA, United States of America.
authors.forename: Shelley
authors.initials: S
authors.lastname: Facente
authors.affiliation: Department of Medicine, School of Medicine, University of California at San Francisco, San Francisco, CA, United States of America.|Blood Systems Research Institute, San Francisco, California, United States of America.
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Keating
authors.affiliation: Department of Medicine, School of Medicine, University of California at San Francisco, San Francisco, CA, United States of America.|Blood Systems Research Institute, San Francisco, California, United States of America.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Busch
authors.affiliation: Public Health England, London, United Kingdom.
authors.forename: Gary
authors.initials: G
authors.lastname: Murphy
authors.affiliation: The South African DST/NRF Centre of Excellence in Epidemiological Modelling and Analysis (SACEMA), Stellenbosch University, Stellenbosch, South Africa.
authors.forename: Alex
authors.initials: A
authors.lastname: Welte
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.|Laboratory of Immunoregulation, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH, Baltimore, MD, United States of America.
authors.forename: Thomas
authors.initials: T
authors.lastname: Quinn
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.
authors.forename: Susan H
authors.initials: SH
authors.lastname: Eshleman
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States of America.|Laboratory of Immunoregulation, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, NIH, Baltimore, MD, United States of America.
authors.forename: Oliver
authors.identifier: http://orcid.org/0000-0002-6429-4760
authors.initials: O
authors.lastname: Laeyendecker
mesh_terms: D003430:Cross-Sectional Studies; D059788:Dried Blood Spot Testing; D015658:HIV Infections / Q000097:blood* / Q000453:epidemiology; D015497:HIV-1 / Q000302:isolation & purification*; D006801:Humans; D015994:Incidence; D019562:Viral Load