Precise performance when meeting HIV challenges

The Abbott RealTime HIV-1 assay provides:

• Enhanced precision: Provides strong performance measuring low-level viremia
• Accurate monitoring: Confidence to reliably detect changes to patient's response status
• Unique assay design: Partially double stranded probe, highly conserved target region and specific temperature profile ensure reliable detection of all groups and subtypes

Addressing the Challenges of HIV

The Abbott RealTime HIV-1 assay is engineered to address the challenges of HIV:

The genetic heterogeneity of HIV-1 presents a significant challenge to the development of assays capable of reliably detecting and quantifying HIV-1 nucleic acid. Although certain subtypes dominate in specific areas, studies show that the spread of different HIV-1 groups and subtypes is increasing globally.

HIV-1 diversity can be attributed to:

• Error-prone reverse transcriptase enzyme
• Recombination of subtypes
• Cross-specific transmission 

Physiological Blip or Random Assay Variation?

A detectable low-level viremia following a previous viral load below the limit of detection or undetectable may be:  

• A true increase of the viral load level, such as the first step toward the development of resistance 
• A physiological blip caused by e.g. release of virus from a reservoir 
• An assay artifact measurement such as random variations (imprecision) around the decision point 

Each HIV-1 positive viral load result can generate anxiety among both clinicians and patients concerning the adequacy of therapy. In cases where these results are driven by random assay variation this may lead to unnecessary additional testing.

Abbott RealTime HIV-1 assay demonstrates high precision around the clinical decision point and minimizes the risk of reporting a low-level viremia result due to random assay variation.

The coefficient of variation observed in low viral load patient specimens (three patient samples with viral load below 100 coples/mL; 10 replicates each, was significantly lower with Abbott RealTime HIV (26%-31%) than that of a comparator assay (37-59%).
 

Detection of HIV-1 Subtypes and Groups

A total of 90 clinical specimens, ten of each Group M subtype (A, B, C, D, CRF01-AE, F, CRF02-AG, G) and of Group O, were tested with the RealTime HIV-1 assay and by two other approved HIV-1 quantitative assays referred to as Comparator 1 (FDA-approved version used) and Comparator 2 (CE-Marked version used). The numbers in parentheses are the number of specimens that had lower quantitation values by more than 1.00 log copies/mL when compared to RealTime HIV-1 assay.

Correlation to Comparator Assay

Intended Use

The Abbott RealTime HIV-1 assay is an in vitro reverse transcription-polymerase chain reaction (RT-PCR) assay for the quantitation of Human Immunodeficiency Virus type 1 (HIV-1) in whole blood spotted on cards as dried blood spots (DBS) (i.e. obtained via venipuncture or capillary blood) or human plasma from HIV-1 infected individuals. The Abbott RealTime HIV-1 assay is intended for use in conjunction with clinical presentation and other laboratory markers for disease prognosis and for use as an aid in assessing viral response to antiretroviral treatment as measured by changes in plasma HIV-1 RNA levels. This assay is not intended to be used as a donor screening test for HIV-1 or as a diagnostic test to confirm the presence of HIV-1 infection.

Design Philosophy

The unique combination of Abbott RealTime HIV-1 assay design features ensures reliable detection of all HIV-1 groups and subtypes with a high degree of precision.

Precise Performance When Measuring Low-Level Viremia

Precise External Calibration: This assay's design features allow the use of two-point external calibration for accurate and precise quantification. 

Primers and Probe Target

Primers and probe are targeted to the integrase region of the polymerase gene. Selection of the conserved target region (integrase region of polymerase gene) was facilitated by the Abbott HIV Global Surveillance Program. Abbott RealTime HIV-1 continues to demonstrate the capacity to tolerate mutations with no impact on assay performance. 

Partially Double Stranded Probe Design

Unique Probe Design:  A new class of probes, the partially double stranded probe, developed by Abbott allows for accurate quantification across genetically polymorphic targets.

Cycling Conditions: Low Temperature Read Cycles

Optimal Cycling Conditions: Unique probe design ensures optimization of cycling conditions, which includes lower read temperature, contributing to mismatch tolerance.