Quantification of Viral Loads Lower than 50 Copies per Milliliter by Use of the Cobas AmpliPrep/Cobas TaqMan HIV-1 Test, Version 2.0, Can Predict the Likelihood of Subsequent Virological Rebound to >50 Copies per Milliliter

Abstract

b After 1 year of follow-up, patients on HAART with a baseline viral load (VL) of <20 copies/ml showed significantly lower odds of virological rebound to two consecutive VLs of >50 copies/ml than those with baseline VLs of 20 to 39 and 40 to 49 (P < 0.001). The time to virological rebound was also significantly shorter (P < 0.001) for the groups with baseline VLs of 20 to 39 and 40 to 49. T he number of patients failing antiretroviral treatment with low-level viremia (e.g., a viral load [VL] ranging from 40 to 1,000 copies/ml) is increasing (1, 2), and special interest has been shown in the clinical significance of this finding. During the last years of the past decade, commercial assays for measuring viral loads reduced their detection limits (3-6), which shifted from 50 to 40 to 20 copies/ml, depending on the assay (7). Recently, a number of reports (8-12) have focused on the clinical significance of very low-level viremia (e.g., viral-load levels below 20 or between 20 and 50 copies/ml). The use of different assays or a different sample size, and even different baseline characteristics of the studies, may partially explain some of the contradictory findings of the studies. In addition, high variability of the Cobas Ampliprep/Cobas TaqMan v2.0 assay at levels of 20 and 40 HIV copies/ml has been described (13).Since the introduction in our institution of Cobas TaqMan v2.0 (Roche Diagnostics) in June 2009, the lower detection cutoff of 50 copies/ml was shifted to 20 copies/ml, and this new threshold was reported to physicians treating HIV and thus used for making clinical decisions.In this retrospective cohort study, we have investigated the clinical significance of having a viral load between 20 and 50 copies/ml in terms of the odds for a viral-load rebound to more than 50 copies/ml or 400 copies/ml 1 year after testing. When possible, the emergence of resistance was also investigated.All adult HIV patients (Ͼ18 years old) who were on highly active antiretroviral therapy (HAART) with an available follow-up 12 months (median, 12.42 months; interquartile range [IQR], 11.73 to 13.80 months) after a viral-load test result below 50 copies/ml (time zero [T 0 ]) using the Cobas TaqMan v2.0 assay were included. When needed, resistance testing of very low-level viral loads was performed using a concentration step (14) prior to following the standard procedure of the Trugene HIV genotyping kit (Siemens NAD). Two hundred ninety patients met the inclusion criteria, and the pre-T 0 CD4 count, time (in years) with a VL of Ͻ50 before T 0 , number of years on HAART, and type of HAART regimen were retrieved from their medical records. Virological rebound was considered when two consecutive viral loads were recorded. Two definitions of virological rebound were evaluated: (i) rebound to more than 50 copies/ml, confirmed in two consecutive samples, and (ii) rebound to more than 400 copies/ ml, also confirmed in two consecutive samples. The time to virological rebound in months was also recorded. The baseline characteristics were ...

Significance and Clinical Management of Persistent Low-Level Viremia and Very-Low-Level Viremia in HIV-1-Infected Patients

“…Studies that evaluated the risk of viral rebound among patients with detectable viremia below the quantification limits of conventional assays differed in their results ( Table 2). Most of the studies demonstrated an increased risk of viral rebound of Ͼ50 cpm among patients with detected viremia below the limits of conventional assays (43,48,(50)(51)(52), while two did not reveal an association (42,49). In one of the studies, Doyle et al Table 5).…”

Evaluation of the Aptima HIV-1 Quant Dx Assay using plasma and dried blood spots

“…In the United States, the most commonly performed virus load test is the Cobas AmpliPrep/ Cobas TaqMan HIV-1 Test v2.0 (CAP/CTM) (Roche Molecular Systems, Pleasanton, CA), a U.S. Food and Drug Administration (FDA) in vitro diagnostic (IVD) that provides high-throughput, sample-to-answer testing with real-time, reverse transcriptase PCR (RT-PCR)-based quantitation. This assay is well studied and provides a benchmark for virus load testing performance in the United States and globally (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). A recently developed test for virus load is the Aptima HIV-1 Quant Dx assay (Aptima) performed on the fully automated Panther system (both from Hologic Inc., San Diego, CA).…”

Ability of Two Commercially Available Assays (Abbott RealTi m e HIV-1 and Roche Cobas AmpliPrep/Cobas TaqMan HIV-1 Version 2.0) To Quantify Low HIV-1 RNA Levels (<1,000 Copies/Milliliter): Comparison with Clinical Samples and NIBSC Working Reagent for Nucleic Acid Testing Assays

“…Furthermore, even HIV-RNA levels Ͻ50 copies/ml (residual viremia [RV]) are receiving increased attention, because this level may announce beforehand a viral rebound risk in a manner that is directly proportional to the extent of the RV (8)(9)(10)(11)(12).…”