title: Dual testing algorithm of BED-CEIA and AxSYM Avidity Index assays performs best in identifying recent HIV infection in a sample of Rwandan sex workers.
abstract: BACKGROUND
  To assess the performance of BED-CEIA (BED) and AxSYM Avidity Index (Ax-AI) assays in estimating HIV incidence among female sex workers (FSW) in Kigali, Rwanda.
  
  
  RESULTS
  Eight hundred FSW of unknown HIV status were HIV tested; HIV-positive women had BED and Ax-AI testing at baseline and ≥12 months later to estimate assay false-recent rates (FRR). STARHS-based HIV incidence was estimated using the McWalter/Welte formula, and adjusted with locally derived FRR and CD4 results. HIV incidence and local assay window periods were estimated from a prospective cohort of FSW. At baseline, 190 HIV-positive women were BED and Ax-AI tested; 23 were classified as recent infection (RI). Assay FRR with 95% confidence intervals were: 3.6% (1.2-8.1) (BED); 10.6% (6.1-17.0) (Ax-AI); and 2.1% (0.4-6.1) (BED/Ax-AI combined). After FRR-adjustment, incidence estimates by BED, Ax-AI, and BED/Ax-AI were: 5.5/100 person-years (95% CI 2.2-8.7); 7.7 (3.2-12.3); and 4.4 (1.4-7.3). After CD4-adjustment, BED, Ax-AI, and BED/Ax-AI incidence estimates were: 5.6 (2.6-8.6); 9.7 (5.0-14.4); and 4.7 (2.0-7.5). HIV incidence rates in the first and second 6 months of the cohort were 4.6 (1.6-7.7) and 2.2 (0.1-4.4).
  
  
  CONCLUSIONS
  Adjusted incidence estimates by BED/Ax-AI combined were similar to incidence in the first 6 months of the cohort. Furthermore, false-recent rate on the combined BED/Ax-AI algorithm was low and substantially lower than for either assay alone. Improved assay specificity with time since seroconversion suggests that specificity would be higher in population-based testing where more individuals have long-term infection.
authors.affiliation: Mailman School of Public Health-Columbia University, New York, New York, United States of America. braunstein.sarah@gmail.com
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Braunstein
authors.forename: Denis
authors.initials: D
authors.lastname: Nash
authors.forename: Andrea A
authors.initials: AA
authors.lastname: Kim
authors.forename: Ken
authors.initials: K
authors.lastname: Ford
authors.forename: Lambert
authors.initials: L
authors.lastname: Mwambarangwe
authors.forename: Chantal M
authors.initials: CM
authors.lastname: Ingabire
authors.forename: Joseph
authors.initials: J
authors.lastname: Vyankandondera
authors.forename: Janneke H H M
authors.initials: JH
authors.lastname: van de Wijgert
mesh_terms: D015492:AIDS Serodiagnosis / Q000379:methods*; D000328:Adult; D000465:Algorithms; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D012432:Rwanda / Q000453:epidemiology; D011477:Sex Work