RealTime HIV-1 Viral Load

For In Vitro Diagnostic Use 

The Abbott RealTime HIV-1 Viral Load assay is for quantitation of Human Immunodeficiency Virus 1 (HIV-1).

icon-pdf.pngAbbott RealTime HIV-1 Package Insert (PDF – 1.7 MB) For Information Only - Not a Controlled Copy

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Description
 

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.

Abbott RealTime HIV-1 assay quantification comparison chart
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

GROUP/SUBTYPES N REALTIME DETECTED COMPARATOR 1 DETECTED COMPARATOR 2 DETECTED
M/Subtype A 10 10 10 (1) 10 (1)
M/Subtype B 10 10 10 (0) 10 (0)
M/Subtype C 10 10 10 (0) 10 (0)
M/Subtype D 10 10 10 (0) 10 (0)
M/Subtype AE 10 10 10 (0) 10 (0)
M/Subtype F 10 10 10 (0) 10 (0)
M/Subtype AG 10 10 10 (3) 10 (1)
M/Subtype G 10 10 10 (2) 10 (1)
Group O 10 10 0 (NA) 7 (7)
N = number of specimens tested
 
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
Abbott RealTime HIV-1 Correlation to Comparator Assay

A total of 301 specimens collected from HIV-1 infected patients were tested with the RealTime HIV-1 assay at three external sites and with the comparator method at a central laboratory site. The results from a total of 259 specimens that fell within the common assay dynamic range were analyzed by the Passing-Bablok linear regression method. 

Indications and Limitations of Use

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) on the automated m2000 System in human plasma from HIV-1 infected individuals over the range of 40 to 10,000,000 copies/mL. 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.

Limitations

  • Human plasma specimens collected in ACD-A or EDTA tubes may be used.
  • A specimen with a result of "Target not detected" cannot be presumed to be negative for HIV-1 RNA.
  • As with any diagnostic test, results from the Abbott RealTime HIV-1 assay should be interpreted in conjunction with other clinical and laboratory findings.

 

CAUTION: United States Federal law restricts this device to sale and distribution to or on the order of a physician or to a clinical laboratory; and use is restricted to, by, or on the order of a physician.

Design
 

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.

Abbott RealTime HIV-1 assay design features
 

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. 

Abbott RealTime HIV-1 assay external calibration

Utility of external calibration curve reduces variability of the viral load calculation compared to an internal calibration as there are no competitive effects in the PCR reaction. Random assay variation is minimized, resulting in highly accurate viral quantification at the clinical decision point and providing confidence in a patient's response to therapy.
 

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. 

Abbott RealTime HIV-1 assay conserved target region

The integrase region of the polymerase gene is a conserved region of the HIV-1 genome.
 

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.

Abbott RealTime HIV-1 assay probe design

Extended length - higher mismatch tolerance: in the absence of target, the probe hybridizes to the quencher oligonucleotide, preventing fluorescent signal generation.
 

Abbott RealTime HIV-1 assay probe design

In the presence of target, the probe prefers to hybridize with the target sequence, disassociating from the quencher oligonucleotide and allowing fluorescent detection.
 

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.

Abbott RealTime HIV-1 assay low temp read cycles

 
Specifications
 
 
 
Abbott RealTime HIV-1Plasma
Sensitivity 40 copies/mL for 1.0 mL sample volume
40 copies/mL for 0.6 mL sample volume
75 copies/mL for 0.5 mL sample volume
150 copies/mL for 0.2 mL sample volume
Linear Range 40 copies/mL (1.6 log copies/mL) to 10 million copies/mL (7.0 log copies/mL)
Specificity 100%1
Target region Integrase region of polymerase gene
Subtype Detection Group M subtypes A—H, Group O and Group N
Internal control Non-competitive pumpkin RNA, added to lysis buffer during extraction
Standardization Virology Quality Assurance (VQA) Laboratory of the AIDS Clinical Trial Group World Health Organization (WHO) 1st International Standard for HIV-1 RNA (97/656)
Specimen Type Plasma (ACD-A and EDTA)
Input volume 0.2 mL; 0.5 mL; 0.6 mL; 1.0 mL
Sample preparation m2000sp
1The specificity of the RealTime HIV-1 assay was evaluated at three external sites by testing 514 HIV-1 seronegative plasma specimens from volunteer blood donors. HIV-1 RNA was not detected for all 514 specimens and the RealTime HIV-1 assay specificity was estimated to be 100% (514/514), (95% CI 99.28 to 100%).

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