Cobas ampliprep/cobas TaqMan HIV-1 v2.0 assay: consequences at the cohort level

Prevalence and risk factors for subclinical atherosclerosis amongst adults living with HIV in University of Abuja Teaching Hospital, Gwagwalada

Background

Subclinical atherosclerosis characterizes cardiovascular diseases (CVD), and Human Immunodeficiency Virus (HIV) infection and antiretroviral therapy (ART) are identified risk factors for atherosclerosis. Meanwhile, data on HIV and atherosclerosis in Nigeria are limited.

Objectives

We sought to estimate the prevalence of subclinical atherosclerosis and associated risk factors amongst adult persons living with HIV/AIDS (PLHIV) enrolled at University of Abuja Teaching Hospital, Gwagwalada, Abuja (UATH).

Methods

This was a cross-sectional study of 277 consecutively selected PLHIV ≥18 years enrolled for HIV care and treatment at UATH. Pretested structured questionnaire was used to collect data from consenting ART-experienced and ART-naïve patients on risk factors of atherosclerosis. Carotid intima media thickness (CIMT) ≥0.71 mm as measured by Doppler ultrasonography was used to identify patients with sub-clinical atherosclerosis. Two logistic regression models with (Model-A) and without (Model-B) traditional risk factors were fitted to identify risk factors of subclinical atherosclerosis.

Results

Participants' mean age was 39.44 ± 10.71 years with female preponderance (64.26%). Overall prevalence of subclinical atherosclerosis was 43.32% (62.25% in ART-experienced). Model-A identified male sex [AOR 4.33(1.74-10.76), p = 0.002], advancing age [30-39 years AOR 5.95(1.31-26.96), p = 0.021]; ≥40 years AOR 19.51(4.30-88.56), p ≤ 0.001), advancing HIV infection [≥WHO stage II AOR 4.19(1.11-15.92), p = 0.035], hypercholesterolemia [AOR 3.88(1.47-10.25), p ≤ 0.001] and ≥5 year duration on ART [AOR 9.05(3.16-25.92), p ≤ 0.001] as risk factors of subclinical atherosclerosis. In Model-B (excluding traditional risk factors) on the other hand, advancing HIV infection [≥WHO stage II AOR 3.93(1.19-13.042), p = 0.025] and duration on ART [≥5 years AOR 11.43(4.62-28.29), p = 0.001] were found as risk factors of subclinical atherosclerosis.

Conclusion

Subclinical atherosclerosis was higher in ART-experienced patients, and this was irrespective of presence or absence of traditional risk factors. And advancing HIV disease and duration on ART were found as significant risk factors for subclinical atherosclerosis. We therefore recommend routine CVD risk screening in PLHIV.

Multicenter evaluation of the cobas® HIV-1 quantitative nucleic acid test for use on the cobas® 4800 system for the quantification of HIV-1 plasma viral load

BACKGROUND AND OBJECTIVES

Measurement of HIV-1 viral load (VL) is necessary to monitor treatment efficacy in patients receiving antiretroviral therapy. We evaluated the performance of the cobas® HIV-1 quantitative nucleic acid test for use on the cobas® 4800 system ("cobas 4800 HIV-1").

METHODS

Limit of detection, linearity, accuracy, precision, and specificity of cobas 4800 HIV-1, COBAS® AmpliPrep/COBAS® Taqman® HIV-1 version 2.0 (CAP/CTM HIV-1 v2) and Abbott RealTime HIV-1 were determined in one or two out of three sites.

RESULTS

The limit of detection of the cobas 4800 HIV-1 for 400 μL and 200 μL input volumes was 14.2 copies/mL (95% CI: 12.5-16.6 copies/mL) and 43.9 copies/mL (37.7-52.7 copies/mL), respectively. Cobas 4800 HIV-1 demonstrated 100% specificity, and results were linear for all analyzed group M HIV-1 subtypes. Precision was high (SD < 0.19 log₁₀) across all measured ranges, reagent lots and input volumes. Correlation between cobas 4800 HIV-1 and CAP/CTM HIV-1 v2 or RealTime HIV-1 was high (R² ≥ 0.95). Agreement between cobas 4800 HIV-1 and CAP/CTM HIV-1 v2 was 96.5% (95.0%-97.7%) at a threshold of 50 copies/mL, and 97.2% (95.8%-98.3%) at 200 copies/mL. Agreement between cobas 4800 HIV-1 and RealTime HIV-1 was 96.6% (93.4%-98.5%) at 50 copies/mL, and 97.0% (94.0%-98.8%) at 200 copies/mL. The mean difference between cobas 4800 HIV-1 and CAP/CTM HIV-1 v2 or RealTime HIV-1 was -0.10 log₁₀ or 0.01 log₁₀, respectively.

CONCLUSIONS

The cobas 4800 HIV-1 test is highly sensitive, accurate and correlated well with other assays, including agreement around clinically relevant thresholds, indicating minimal overall VL quantification differences between tested platforms.

Comparison of a new in-house HIV-1 TaqMan real-time PCR and three commercial HIV-1 RNA quantitative assays

OBJECTIVES

The aim of this study was to compare the analytical performance of an In-House HIV-1 viral load determination technique with three commercial kits including COBAS^® AmpliPrep, RealStar^®, and RTA^® HIV-1 Real-Time PCR.

RESULTS

A total of 100 HIV-1 suspicious plasma samples were tested by the In-House TaqMan^® Real-Time PCR assay along with the above-mentioned kits. Comparative analysis between In-House and reference method (COBAS^® AmpliPrep/COBAS^® TaqMan^® HIV-1 Test version 2.0) showed high concordance with a mean difference of 0.08 log₁₀ copies/ml. All samples results were within -0.16-0.31 log₁₀ copies/ml. A suitable correlation was obtained with a coefficient (R²) of 0.82 between the In-House assay and RTA^® Kit, however, two positive samples were not detected. The lowest agreement was detected with RealStar^® HIV Kit 1.0 (R² = 0.49, r = 0.7).

CONCLUSIONS

The newly developed method has suitable sensitivity, accuracy, and precision. In addition, it is cost-effective and can be an alternative in all laboratories.

A Single Quantifiable Viral Load Is Predictive of Virological Failure in Human Immunodeficiency Virus (HIV)-Infected Patients on Combination Antiretroviral Therapy: The Austrian HIV Cohort Study

Background.  Viral loads (VLs) detectable at low levels are not uncommon in patients on combination antiretroviral therapy (cART). We investigated whether a single quantifiable VL predicted virological failure (VF). Methods.  We analyzed patients receiving standard regimens with at least 1 VL measurement below the limit of quantification (BLQ) in their treatment history. The first VL measurement after 6 months of unmodified cART served as baseline VL for the subsequent analyses of the time to reach single VL levels of ≥200, ≥400, and ≥1000 copies/mL. Roche TaqMan 2.0 was used to quantify human immunodeficiency virus-1 ribonucleic acid. Factors associated with VF were determined by Cox proportional hazards models. Results.  Of 1614 patients included in the study, 68, 44, and 34 experienced VF ≥200, ≥400, and ≥1000 copies/mL, respectively. In multivariable analyses, compared with patients who were BLQ, a detectable VL ≤ 50 and VL 51-199 copies/mL predicted VF ≥ 200 copies/mL (hazards ratio [HR] = 2.19, 95% confidence interval [CI] = 1.06-4.55 and HR = 4.21, 95% CI = 2.15-8.22, respectively). In those with VL 51-199 copies/mL, a trend for an increased risk of VF ≥400 and VF ≥1000 copies/mL could be found (HR = 2.13, 95% CI = 0.84-5.39 and HR = 2.52, 95% CI = 0.96-6.60, respectively). Conclusions.  These findings support closer monitoring and adherence counseling for patients with a single measurement of quantifiable VL <200 copies/mL.

Aptima HIV-1 Quant Dx--A fully automated assay for both diagnosis and quantification of HIV-1

BACKGROUND

Separate assays are available for diagnosis and viral load (VL) monitoring of HIV-1. Studies have shown that using a single test for both confirmatory diagnosis and VL increases linkage to care.

OBJECTIVE

To validate a single assay for both diagnosis and VL monitoring of HIV-1 on the fully automated Panther platform.

STUDY DESIGN

Validate the assay by assessing specificity, sensitivity, subtype detection, seroconversion, reproducibility and linearity. Also assess diagnostic agreement with the Procleix(®) Ultrio Elite™ discriminatory assay (Procleix), and agreement of VL results (method comparison) with Ampliprep/COBAS TaqMan HIV-1 version 2.0 (CAP/CTM), using clinical samples.

RESULTS

The assay was specific (100%) and sensitive with a 95% limit of detection of 12 copies/mL with the 3rd WHO standards. Aptima detected HIV in seroconversion panels 6 and 11 days before p24 antigen and antibody tests, respectively. Diagnostic agreement with Procleix, was 100%. Regression analysis showed good agreement of VL results between Aptima and CAP/CTM with a slope of 1.02, intercept of 0.07, and correlation coefficient (R(2)) of 0.97. Aptima was more sensitive than CAP/CTM. Equivalent quantification was seen on testing clinical samples and isolates belonging to HIV group M, N, O and P and commercially available subtype panels. Assay results were linear (R(2) 0.9994) with standard deviation of <0.17 log copies across assay range.

CONCLUSIONS

The good specificity, sensitivity, precision, subtype performance and clinical agreement with other assays demonstrated by Aptima combined with the complete automation provided by the Panther platform makes Aptima a good candidate for both VL monitoring and diagnosis of HIV-1.

Factors Associated with Low-Level Viraemia and Virological Failure: Results from the Austrian HIV Cohort Study

Background

In human immunodeficiency virus treatment adequate virological suppression is warranted, nevertheless for some patients it remains a challenge. We investigated factors associated with low-level viraemia (LLV) and virological failure (VF) under combined antiretroviral therapy (cART).

Materials and Methods

We analysed patients receiving standard regimens between 1^st July 2012 and 1^st July 2013 with at least one viral load (VL) measurement below the quantification limit (BLQ) in their treatment history. After a minimum of 6 months of unmodified cART, the next single VL measurement within 6 months was analysed. VF was defined as HIV RNA levels ≥200 copies/mL and all other quantifiable measurements were classified as LLV. Factors associated with LLV and VF compared to BLQ were identified by logistic regression models.

Results

Of 2276 participants, 1972 (86.6%) were BLQ, 222 (9.8%) showed LLV and 82 (3.6%) had VF. A higher risk for LLV and VF was shown in patients with cART interruptions and in patients with boosted PI therapy. The risk for LLV and VF was lower in patients from centres using the Abbott compared to the Roche assay to measure VL. A higher risk for LLV but not for VF was found in patients with a higher VL before cART [for >99.999 copies/mL: aOR (95% CI): 4.19 (2.07–8.49); for 10.000–99.999 copies/mL: aOR (95% CI): 2.52 (1.23–5.19)] and shorter cART duration [for <9 months: aOR (95% CI): 2.59 (1.38–4.86)]. A higher risk for VF but not for LLV was found in younger patients [for <30 years: aOR (95% CI): 2.76 (1.03–7.35); for 30–50 years: aOR (95% CI): 2.70 (1.26–5.79)], people originating from high prevalence countries [aOR (95% CI): 2.20 (1.09–4.42)] and in male injecting drug users [aOR (95% CI): 2.72 (1.38–5.34)].

Conclusions

For both VF and LLV, factors associated with adherence play a prominent role. Furthermore, performance characteristics of the diagnostic assay used for VL quantification should also be taken into consideration.

Transient detectable viremia and the risk of viral rebound in patients from the Swiss HIV Cohort Study

BACKGROUND

Temporary increases in plasma HIV RNA ('blips') are common in HIV patients on combination antiretroviral therapy (cART). Blips above 500 copies/mL have been associated with subsequent viral rebound. It is not clear if this relationship still holds when measurements are made using newer more sensitive assays.

METHODS

We selected antiretroviral-naive patients that then recorded one or more episodes of viral suppression on cART with HIV RNA measurements made using more sensitive assays (lower limit of detection below 50 copies/ml). We estimated the association in these episodes between blip magnitude and the time to viral rebound.

RESULTS

Four thousand ninety-four patients recorded a first episode of viral suppression on cART using more sensitive assays; 1672 patients recorded at least one subsequent suppression episode. Most suppression episodes (87 %) were recorded with TaqMan version 1 or 2 assays. Of the 2035 blips recorded, 84 %, 12 % and 4 % were of low (50-199 copies/mL), medium (200-499 copies/mL) and high (500-999 copies/mL) magnitude respectively. The risk of viral rebound increased as blip magnitude increased with hazard ratios of 1.20 (95 % CI 0.89-1.61), 1.42 (95 % CI 0.96-2.19) and 1.93 (95 % CI 1.24-3.01) for low, medium and high magnitude blips respectively; an increase of hazard ratio 1.09 (95 % CI 1.03 to 1.15) per 100 copies/mL of HIV RNA.

CONCLUSIONS

With the more sensitive assays now commonly used for monitoring patients, blips above 200 copies/mL are increasingly likely to lead to viral rebound and should prompt a discussion about adherence.

Comparative performance of the new Aptima HIV-1 Quant Dx assay with three commercial PCR-based HIV-1 RNA quantitation assays

BACKGROUND

Quantitative measurement of HIV-1 RNA levels in plasma ('viral load') plays a central role in clinical management. The choice of assay platform can influence results and treatment decisions.

OBJECTIVE

To compare the analytical performance of the new TMA-based Hologic Aptima(®) HIV-1 Quant Dx assay with that of three PCR-based assays: Abbott RealTime HIV-1, Qiagen Artus(®) HI Virus-1 QS-RGQ, and Roche CAP/CTM HIV-1 Test v2.

STUDY DESIGN

Assay performance was evaluated using Acrometrix HIV-1 RNA Standard panels; the 3rd WHO HIV-1 RNA International Standard (12-500 copies/ml; 6 dilutions; 9 replicates); and plasma samples from 191 HIV-positive patients.

RESULTS

Aptima showed high (>0.99) precision, accuracy and concordance with the Acrometrix Standards across a wide dynamic range (2.0-6.7 log10copies/ml). Variance caused up to 2.1 (Aptima), 1.7 (RealTime), 7.5 (Artus), and 1.9 (CAP/CTM) fold changes in the International Standard quantifications at 50-500 copies/ml. HIV-1 RNA detection rates in plasma samples were 141/191 (74%), 119/191 (62%), 108/191 (57%), and 145/191 (76%) for Aptima, RealTime, Artus and CAP/CTM, respectively. For categorising samples either side of 50 copies/ml, Aptima had excellent agreement with RealTime (kappa 0.92; 95% CI 0.87-0.98); lowest agreement was with Artus (kappa 0.79; 95%CI 0.70-0.88). Aptima quantifications were mean 0.12 and 0.06 log10copies/ml higher compared with RealTime and CAP/CTM, respectively, and 0.05 log10copies/ml lower compared with Artus. Limits of agreement were narrowest when comparing Aptima to RealTime.

CONCLUSIONS

The new Aptima HIV assay is sensitive, precise, and accurate. HIV assays exhibit discordance at low HIV-1 RNA copy numbers.

Evaluation of the NucliSens EasyQ v2.0 assay in comparison with the Roche Amplicor v1.5 and the Roche CAP/CTM HIV-1 Test v2.0 in quantification of C-clade HIV-1 in plasma

Human immunodeficiency virus type 1 (HIV-1) genetic diversity poses a challenge to reliable viral load monitoring. Discrepancies between different testing platforms have been observed, especially for non-clade-B virus. Therefore we compare, in antiretroviral therapy (ART)-naïve South African subjects predominantly infected with HIV-1 clade-C, three commercially available assays: the COBAS AmpliPrep/COBAS TaqMan HIV-1 Test version 2.0 by Roche (CAP/CTM v2.0), the BioMérieux NucliSens Version 2.0 Easy Q/Easy Mag (NucliSens v2.0) and the Roche COBAS Amplicor HIV-1 Monitor Test Version 1.5 (Amplicor v1.5). Strong linear correlation was observed and Bland-Altman analyses showed overall good agreement between the assays with mean viral load differences of 0.078 log cp/ml (NucliSens v2.0 – Amplicor v1.5), 0.260 log cp/ml (CAP/CTM v2.0 – Amplicor v1.5) and 0.164 log cp/ml (CAP/CTM v2.0 – NucliSens v2.0), indicating lower mean viral load results for the Amplicor v1.5 and higher mean readings for the CAP/CTM v2.0. Consistent with observations following previous comparisons of CAP/CTM v2.0 versus Amplicor v1.5, the CAP/CTM v2.0 assay detected low-level viremia (median 65 cp/ml) in more than one-third of those in whom viremia had been undetectable (<20 cp/ml) in assays using the NucliSens platform. These levels of viremia are of uncertain clinical significance but may be of importance in early detection of ART resistance in those on treatment. Overall the three assays showed good comparability of results but with consistent, albeit relatively small, discrepancies for HIV-1 clade-C samples, especially in the low-viremic range that should be taken into account when interpreting viral load data.

Ability of two commercially available assays (Abbott RealTime 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

Concordance between molecular assays may be suboptimal at low HIV-1 viremia levels (<1,000 copies/ml); therefore, it may be difficult to define and compare virologic endpoints for successful and failed therapy. We compared two commercial assays (the Abbott RealTime HIV-1 and the Roche Cobas AmpliPrep/TaqMan HIV-1 version 2.0) for their ability to detect and quantify low viral loads. A comparison was performed using 167 residual clinical samples (with values ranging from "not detected" to 1,000 copies/ml, as measured by the Abbott assay) and the National Institute and Biological Standards and Control (NIBSC) HIV-1 RNA working reagent 1 for nucleic acid amplification techniques (NAT) assays (serially diluted to a range from 1 to 1,000 copies/ml). Quantitative results were compared using Lin's concordance correlation coefficient and a Bland-Altman plot. Concordance with the qualitative results was measured by Cohen's kappa statistic. With clinical samples, the degree of interassay concordance of the qualitative results at a 40-copies/ml HIV-1 RNA threshold was substantial (κ = 0.762); the correlation among the quantified samples was suboptimal (concordance correlation coefficient, 0.728; P < 0.0001); the mean difference of the values between the Roche and Abbott assays was 0.193 log10 copies/ml. Using the HIV-1 RNA working reagent 1 for NAT assays, the results provided by the Roche assay were, on average, 3 times higher than expected, while the Abbott assay showed high accuracy. The Roche assay was highly sensitive, being able to detect a level as low as 3.5 copies/ml HIV-1 RNA with 95% probability. The performance characteristics of each molecular assay should be taken into account when HIV-1 RNA threshold values for "virologic suppression," "virologic failure," "persistent low viral loads," etc., are defined and indicated in the support of clinical decisions.

Comparative performances of HIV-1 RNA load assays at low viral load levels: results of an international collaboration

Low-level viremia during antiretroviral therapy and its accurate measurement are increasingly relevant. Here, we present an international collaboration of 4,221 paired blood plasma viral load (pVL) results from four commercial assays, emphasizing the data with low pVL. The assays compared were the Abbott RealTime assay, the Roche Amplicor assay, and the Roche TaqMan version 1 and version 2 assays. The correlation between the assays was 0.90 to 0.97. However, at a low pVL, the correlation fell to 0.45 to 0.85. The observed interassay concordance was higher when detectability was defined as 200 copies/ml than when it was defined as 50 copies/ml. A pVL of ∼100 to 125 copies/ml by the TaqMan version 1 and version 2 assays corresponded best to a 50-copies/ml threshold with the Amplicor assay. Correlation and concordance between the viral load assays were lower at a low pVL. Clear guidelines are needed on the clinical significance of low-level viremia.