title: Evidence for a diagnostic window in fourth generation assays for HIV.
abstract: BACKGROUND
  The routine HIV screening essentially depends on the detection of HIV specific antibodies. However, HIV p24 antigen can be detected in individuals with recent HIV infection about 2-18 days prior to seroconversion. New fourth generation HIV screening assays combine the detection of anti-HIV antibodies with the simultaneous detection of HIV p24 antigen. This may result in a reduction of the diagnostic window after primary infection.
  
  
  OBJECTIVE
  The performance of two novel fourth generation assays in routine diagnostic was evaluated.
  
  
  METHODS
  We compared two third generation, two fourth generation and one antigen HIV assays in a case with acute primary HIV infection.
  
  
  RESULTS
  In our case, the HIV infection was detected 11 days earlier with the fourth generation assays compared to third generation assays. Interestingly, after the initial reactive results the fourth generation assays became negative resulting in a second diagnostic window. During this second diagnostic window neither third nor fourth generation HIV assays were reactive. This second diagnostic window was caused by the absence of HIV specific antibodies and the decline of HIV p24 antigen concentrations below the detection limits of the fourth generation assays.
  
  
  CONCLUSIONS
  Fourth generation assays markedly improve the diagnosis of recent HIV infections but the possibility of a second diagnostic window must be considered.
authors.affiliation: Medizinisch-Diagnostisches Gemeinschaftslabor Prof. Gisela Enders und Partner, Rosenbergstrasse 85, D-70193 Stuttgart, Germany. meier@labor-enders.de
authors.forename: T
authors.initials: T
authors.lastname: Meier
authors.forename: E
authors.initials: E
authors.lastname: Knoll
authors.forename: M
authors.initials: M
authors.lastname: Henkes
authors.forename: G
authors.initials: G
authors.lastname: Enders
authors.forename: R
authors.initials: R
authors.lastname: Braun
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D005260:Female; D015483:HIV Antibodies / Q000097:blood*; D016655:HIV Core Protein p24 / Q000097:blood*; D015658:HIV Infections / Q000097:blood / Q000175:diagnosis* / Q000821:virology; D006801:Humans; D012680:Sensitivity and Specificity; D013997:Time Factors
chemical_list: D015483:HIV Antibodies; D016655:HIV Core Protein p24