Comparative evaluation of the performance of the Abbott RealTime HIV-1 assay for measurement of HIV-1 plasma viral load on genetically diverse samples from Greece

Development and interlaboratory agreement of real-time PCR for HPV16 quantification in liquid-based cervical samples

High risk HPV infection is the necessary cause for the development of precancerous and cancerous lesions of the cervix. Among HPV, HPV16 represents the most carcinogenic type. Since the determination of HPV16 DNA load could be clinically useful, we assessed quantitative real-time PCR targeting E6HPV16 and albumin genes on two different platforms. Series of SiHa cells diluted in PreservCyt were used to assess repeatability and reproducibility of two in-house real-time PCR techniques run in two different laboratories to determine HPV16 load. Furthermore, 97 HPV16 positive cervical samples were evaluated to estimate inter-center variability using Bland-Alman plots. As a whole, both techniques presented coefficients of variation for HPV16 load measurement similar to those established for other virus quantification with commercial kits. Moreover, the two real-time PCR techniques showed a very good agreement for HPV16 load calculation. Finally, we emphasize that robust HPV16 DNA quantification requires normalization of viral load by the cell number.

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HPV16 viral load could be a useful biomarker for the management of HPV positive women.

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Coefficient of variation for HPV16 viral load ranged from 7% to 62%.

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HPV16 viral load quantification requires normalization by the cell number.

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HPV16 viral load precision increases with the use of an internal calibrator.

Analytical characteristics and comparative evaluation of Aptima HIV-1 Quant Dx assay with Ampliprep/COBAS TaqMan HIV-1 test v2.0

Background

Quantitation of HIV-RNA is critically important for diagnosis, prognosis, treatment, monitoring and assessment of infectivity in HIV-1 infection. The objective of this study was to assess performance characteristics of the Aptima HIV-1 Quant Dx assay (Aptima), a new transcription mediated amplification (TMA), fully integrated and automated assay from Hologic Inc., San Diego, CA, USA.

The analytical sensitivity, analytical specificity, precision and detection of HIV-1 subtypes were tested based on commercially available international standards or panels. A selected group of 244 anti-HIV-1 (+) plasma samples was used for comparison with Roche COBAS Ampliprep/COBAS TaqMan HIV- 1 test v2.0 (Roche CAP/CTM), (Roche Molecular Systems, Pleasanton, CA).

Results

The 50 and 95 % limit of detection were estimated at 4.9 (95 % CI 3.9–5.7) and 17.6 (15.2–21.2) IU/mL respectively. The specificity was found 99.83 (99.06–99.97) %. The standard deviations and coefficient of variations for panels with 50 and 100 copies/mL (1.7 and 2 log copies/mL) were 0.14 log copies/mL (8.67 %CV) and 0.18 log copies/mL (9.91 %CV) respectively. The detection rate for Aptima and Roche assays was 220/244 (90.2 %) and 217/244 (88.9 %) respectively.

Conclusion

The Aptima assay is a sensitive, specific, precise and accurate test for measuring HIV-1 viral loads and for the detection of HIV-1 infections.

Evaluation of the RealTime HIV-1, Xpert HIV-1, and Aptima HIV-1 Quant Dx Assays in Comparison to the NucliSens EasyQ HIV-1 v2.0 Assay for Quantification of HIV-1 Viral Load

HIV-1 RNA monitoring, both before and during antiretroviral therapy, is an integral part of HIV management worldwide. Measurements of HIV-1 viral loads are expected to assess the copy numbers of all common HIV-1 subtypes accurately and to be equally sensitive at different viral loads. In this study, we compared for the first time the performance of the NucliSens v2.0, RealTime HIV-1, Aptima HIV-1 Quant Dx, and Xpert HIV-1 viral load assays. Plasma samples (n = 404) were selected on the basis of their NucliSens v2.0 viral load results and HIV-1 subtypes. Concordance, linear regression, and Bland-Altman plots were assessed, and mixed-model analysis was utilized to compare the analytical performance of the assays for different HIV-1 subtypes and for low and high HIV-1 copy numbers. Overall, high concordance (>83.89%), high correlation values (Pearson r values of >0.89), and good agreement were observed among all assays, although the Xpert and Aptima assays, which provided the most similar outputs (estimated mean viral loads of 2.67 log copies/ml [95% confidence interval [CI], 2.50 to 2.84 log copies/ml] and 2.68 log copies/ml [95% CI, 2.49 to 2.86 log copies/ml], respectively), correlated best with the RealTime assay (89.8% concordance, with Pearson r values of 0.97 to 0.98). These three assays exhibited greater precision than the NucliSens v2.0 assay. All assays were equally sensitive for subtype B and AG/G samples and for samples with viral loads of 1.60 to 3.00 log copies/ml. The NucliSens v2.0 assay underestimated A1 samples and those with viral loads of >3.00 log copies/ml. The RealTime assay tended to underquantify subtype C (compared to the Xpert and Aptima assays) and subtype A1 samples. The Xpert and Aptima assays were equally efficient for detection of all subtypes and viral loads, which renders these new assays most suitable for clinical HIV laboratories.

Establishment and evaluation of a loop-mediated isothermal amplification (LAMP) assay for the semi-quantitative detection of HIV-1 group M virus

The past decade has witnessed a dramatic increase of anti-retroviral treatment of human immunodeficiency virus (HIV) infected patients in many African countries. Due to costs and lack of currently available commercial viral load assays, insufficient attention has been paid to therapy monitoring through measurement of plasma viral load. This challenge of patient monitoring by tests as viral load, CD4 cell count, and finally HIV drug resistance could reverse achievements already made against HIV/AIDS infection. Loop-mediated isothermal amplification (LAMP) has been shown to be simple, rapid and cost-effective, characteristics which make this assay suitable for viral load monitoring in resource limited settings. This paper describes a revised LAMP assay using primers in the HIV-1 integrase region. The assay can be used for semi-quantitative measurement of HIV-1 group M viral load. The lower limit of detection (LLOD) was determined as 1200copies/mL and lower limit of quantitation (LLOQ) at 9800copies/mL. Sensitivities of 82 and 86% (in 135 and 99 plasma samples respectively from Kenya) and 93% (in 112 plasma samples from Germany) and specificities of 99 and 100% were realized. HIV-1 group O and HIV-2 virus samples were not detected. This LAMP assay has the potential for semi-quantitation of HIV-1 group M viral load in resource limited countries. There is still a need for further improvement by refinement of primers in respect to detection of HIV-1 group M non-B virus.

Systematic review of the performance of HIV viral load technologies on plasma samples

Background

Viral load (VL) monitoring is the standard of care in developing country settings for detecting HIV treatment failure. Since 2010 the World Health Organization has recommended a phase-in approach to VL monitoring in resource-limited settings. We conducted a systematic review of the accuracy and precision of HIV VL technologies for treatment monitoring.

Methods and Findings

A search of Medline and Embase was conducted for studies evaluating the accuracy or reproducibility of commercially available HIV VL assays. 37 studies were included for review including evaluations of the Amplicor Monitor HIV-1 v1.5 (n = 25), Cobas TaqMan v2.0 (n = 11), Abbott RealTime HIV-1 (n = 23), Versant HIV-1 RNA bDNA 3.0 (n = 15), Versant HIV-1 RNA kPCR 1.0 (n = 2), ExaVir Load v3 (n = 2), and NucliSens EasyQ v2.0 (n = 1). All currently available HIV VL assays are of sufficient sensitivity to detect plasma virus levels at a lower detection limit of 1,000 copies/mL. Bias data comparing the Abbott RealTime HIV-1, TaqMan v2.0 to the Amplicor Monitor v1.5 showed a tendency of the Abbott RealTime HIV-1 to under-estimate results while the TaqMan v2.0 overestimated VL counts. Compared to the Amplicor Monitor v1.5, 2–26% and 9–70% of results from the Versant bDNA 3.0 and Abbott RealTime HIV-1 differed by greater than 0.5log₁₀. The average intra and inter-assay variation of the Abbott RealTime HIV-1 were 2.95% (range 2.0–5.1%) and 5.44% (range 1.17–30.00%) across the range of VL counts (2log₁₀–7log₁₀).

Conclusions

This review found that all currently available HIV VL assays are of sufficient sensitivity to detect plasma VL of 1,000 copies/mL as a threshold to initiate investigations of treatment adherence or possible treatment failure. Sources of variability between VL assays include differences in technology platform, plasma input volume, and ability to detect HIV-1 subtypes. Monitoring of individual patients should be performed on the same technology platform to ensure appropriate interpretation of changes in VL.

Prospero registration # CD42013003603.

Low-level viremia is associated with non-B subtypes in patients infected with HIV with virological success following HAART introduction

This prospective study aimed to determine factors associated with detection of very low-level viremia in patients infected with HIV-1 with virological success following HAART introduction. Fifty-seven patients, mostly (n = 51, 89%) treated with a protease inhibitor-based regimen, were included and followed for 2 years. Viral loads were monitored by Abbott m2000 RealTime HIV-1. Patients were classified as (i) HIV-RNA-negative if viral loads remained strictly undetectable (0 copies/ml), or (ii) HIV-RNA-positive if at least one HIV-1 RNA could be detected in 1-49 copies/ml during follow-up. At month 24, 44 patients (77%) were in the HIV-RNA-positive group, whereas 13 (23%) remained without very low-level viremia. Univariate analysis, Kaplan-Meier curves and the Cox proportional hazard model revealed that B subtype was the only predictor of belonging to the HIV-RNA-negative group (HR 3.98; 95% CI 1.08-14.7). This association needs to be confirmed. Further study of the reservoir and the mechanisms of viral latency according to HIV-subtype will also be necessary to develop new therapeutic strategies and eradicate HIV infection.

Quantitation of HIV-1 DNA with a sensitive TaqMan assay that has broad subtype specificity

The increasing diversity of HIV-1 isolates makes virus quantitation challenging, especially when diverse isolates co-circulate in a geographical area. Measuring the HIV-1 DNA levels in cells has become a valuable practical tool for fundamental and clinical research. A quantitative HIV-1 DNA assay was developed based on TaqMan(®) technology. Primers that target the highly conserved LTR region were designed to detect a broad array of HIV-1 variants, including viral isolates from many subtypes, with high sensitivity. Introduction of a pre-amplification step prior to the TaqMan(®) reaction allowed the specific amplification of fully reverse transcribed viral DNA. Execution of the pre-amplification step with a second primer set enables for the exclusive quantitation of the 2-LTR circular HIV-1 DNA form.