title: The risk of a second diagnostic window with 4th generation HIV assays: Two cases.
abstract: BACKGROUND
  Despite the improved sensitivity of the 4th generation combined antigen/antibody HIV assays, detection of HIV in the early phase of an infection may still be ineffective.
  
  
  OBJECTIVE
  Description of two cases that highlight the existence of the "second diagnostic window phase" observed with commonly used sensitive 4th generation HIV assays.
  
  
  METHODS
  Samples were screened with different 4th generation HIV assays. HIV infection was confirmed with an HIV I/II antibody assay, a HIV-1 p24 antigen assay, the INNO-LIA HIV I/II Score Line immunoassay and HIV-1 PCR.
  
  
  RESULTS
  In both investigated cases, the limitations of the 4th generation HIV assays within the second diagnostic window were apparent.
  
  
  CONCLUSIONS
  The overall sensitivity of the commercial 4th generation HIV assays is currently higher than the 3rd generation HIV assays. Nevertheless, the rare occurrence of a second diagnostic window with 4th generation HIV assays strongly suggests that the following up testing algorithms need to be adjusted accordingly.
authors: Blood Transfusion Service SRC Berne, Murtenstrasse 133, 3008 Berne, Switzerland. christoph.niederhauser@bsd-be.ch
authors: C
authors: C
authors: Niederhauser
authors: A
authors: A
authors: Ströhle
authors: M
authors: M
authors: Stolz
authors: F
authors: F
authors: Müller
authors: C
authors: C
authors: Tinguely
mesh_terms: D000328:Adult; D015483:HIV Antibodies / Q000097:blood; D016655:HIV Core Protein p24 / Q000097:blood; D015658:HIV Infections / Q000175:diagnosis*; D015497:HIV-1 / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods; D012367:RNA, Viral / Q000097:blood; D011933:Reagent Kits, Diagnostic; D012680:Sensitivity and Specificity; D055815:Young Adult
chemical_list: D015483:HIV Antibodies; D016655:HIV Core Protein p24; D012367:RNA, Viral; D011933:Reagent Kits, Diagnostic