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The risk of a second diagnostic window with 4th generation HIV assays: Two cases
C Niederhauser1, A Ströhle, M Stolz
1Blood Transfusion Service SRC Berne, Murtenstrasse 133, 3008 Berne, Switzerland. christoph.niederhauser@bsd-be.ch
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.
Objectives:
Description of two cases that highlight the existence of the "second diagnostic window phase" observed with commonly used sensitive 4th generation HIV assays.
Study Design:
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.
