[Utilities and limitations of a real-time PCR based assay for HIV-1 RNA quantification]

This study evaluated the clinical utilities and limitations of HIV 1 RNA quantification using a real time PCR based assay, COBAS AmpliPrep/COBAS Taqman HIV 1 Test(TaqMan), since higher viral loads or wider fluctuations in viral loads have been demonstrated after this assay replaced COBAS AmpliPrep/AMPLICOR HIV-1 Monitor Version 1.5 Ultrasensitive (AMPLICOR).

We conducted a clinical study analyzing HIV-1 RNA levels measured by AMPLICOR assay and by TaqMan assay, CD4+ lymphocyte counts (CD4) and regimens of highly active antiretroviral therapy among patients who were treated in Tokyo Medical University Hospital. HIV 1 RNA levels were measured by an independent clinical laboratory (SRL, Inc.) outside the hospital. More than 50 copies/ml of HIV-1 RNA were demonstrated by TaqMan assay in 47% of 58 specimens in which HIV 1 RNA levels were undetectable (< 50 copies/ml) by AMPLICOR assay. TaqMan assay showed higher levels of HIV-1 RNA in comparison with AMPLICOR assay on correlation analysis. However, there was no tendency toward deterioration of either the serum HIV-1 RNA load or CD4 in patients showing discrepancies between the two assays. There was no correlation between the detection of HIV-1 RNA and the use of certain antiretroviral agents. Repeated assay of specimens from the same collection tube showed large discrepancies.

HIV 1 RNA quantification assay is essential to monitor the effects of antiretroviral therapy. Physicians must remain aware that the TaqMan assay is not yet sufficiently reliable.