A large French prospective cohort of HIV-infected patients: the Nadis Cohort

Integrated analysis of viral blips, residual viremia, and associated factors in people with HIV: Results from a retrospective cohort study

The etiology of viral blips is not yet fully elucidated. One of the hypotheses is that blips reflect variations in residual viremia (RV) near the detectability threshold. In this study, we evaluated whether RV is associated with viral blips and which factors are associated with RV. All treatment regimens in 2010-2020 consisting of two nucleos(-t)ide reverse transcriptase inhibitors and one anchor (integrase strand transfer inhibitor [INSTI], non-nucleoside reverse transcriptase inhibitor [NNRTI], or protease inhibitor [PI]) in people with HIV (PWH) were evaluated for RV (detectable viremia <50 cp/mL) and blips (isolated viral loads [VLs] 50-499 cp/mL between measurements <50 cp/mL). All medical records were reviewed and regimens in which a VL ≥ 50 cp/mL was deemed to result from non-adherence (based on the documented conclusion by the treating physician) were excluded. Factors associated with blips and RV were identified using generalized linear mixed models. In total, 24 518 VLs from 1658 PWH were analyzed. VLs were measured during INSTI- (n = 5119; 20.9%), PI- (n = 8935; 36.4%), and NNRTI-use (n = 10 464; 42.7%). VLs were categorized as blips in 1.4% (n = 332). The 24,186 non-blip VLs were RNAneg (no RV) (n = 15 326; 63.4%), 1-19 cp/mL (n = 6318; 26.1%), 20-49 cp/mL (n = 1620; 6.7%), or <50 cp/mL with an unknown RV level (n = 922; 3.8%). In 193/1658 PWH (11.6%), the RV level was RNAneg in all VLs assessed. RV 1-19 cp/mL and 20-49 cp/mL (vs. RNAneg ) were significantly associated with subsequent viral blips (respective odds ratio 2.66 and 4.90 [95% confidence intervals: 1.98-3.58 and 3.41-7.04]). Zenith VL and use of PIs (vs. INSTIs/NNRTIs) were associated with higher RV and blip odds. This large cohort study showed that blips were associated with higher preceding RV. Both the anchor type and factors previously linked to the latent viral reservoir were associated with RV, suggesting blips having a multifactorial origin.

Lower Incidence of HIV-1 Blips Observed During Integrase Inhibitor-Based Combination Antiretroviral Therapy

BACKGROUND

As the nature of viral blips remains unclear, their occurrence often leads to uncertainty. This study compares blip incidence rates during treatment with different combination antiretroviral therapy anchors.

SETTING

Retrospective cohort study in a tertiary hospital.

METHODS

All antiretroviral regimens between 2010 and 2020 containing 2 nucleos(-t)ide reverse transcriptase inhibitors and 1 anchor in virologically suppressed people living with HIV (PLWH) from our center were evaluated for the occurrence of blips [isolated viral loads (VLs) 50-499 copies/mL between measurements <50 copies/mL]. Factors associated with blips were identified using multivariable generalized estimating equation-based negative binomial models. The relationship between blips and either persistent low-level viremia (consecutive VLs ≥ 50 copies/mL not classified as failure) or virologic failure (consecutive VLs ≥ 200 or 1 VL ≥ 500 copies/mL) was also evaluated.

RESULTS

In total, 308 blips occurred during 3405 treatment courses in 1661 PLWH. Compared with a non-nucleoside reverse transcriptase inhibitor anchor, blip incidence was higher for protease inhibitors (incidence rate ratio 1.37; 95% confidence interval 1.05 to 1.78) and lower for integrase inhibitors (INSTIs) (incidence rate ratio 0.64; 95% confidence interval: 0.43 to 0.96). In addition, blips were associated with higher zenith VL, higher VL test frequency, and shorter time since antiretroviral therapy initiation. PLWH experiencing blips were more likely to demonstrate persistent low-level viremia but not virologic failure. Blips led to extra consultations and measurements.

CONCLUSIONS

INSTI-based regimens display a low number of blips. Although we found no correlation with virologic failure, the occurrence of blips led to an increased clinical burden. Further research is needed to elucidate the implications and underlying mechanisms of these findings.

Risk of HIV viral rebound in HIV infected patients on direct acting antivirals (DAAs) treatment for HCV

BACKGROUND

The dynamic of HIV-viral load (VL) remains poorly investigated in HIV/HCV patients under direct acting antivirals (DAAs).

METHODS

We retrospectively evaluated HIV-VL at baseline (BL) during and up to 24 weeks post-DAAs in a cohort of 305 HIV-1/HCV patients, on ART and with no HIV virological failure (VF) in the 6 months before treatment with DAAs; during the period of observation VF was defined as confirmed VL≥50 copies/mL; virological blips (VB, transient, not confirmed, VL ≥50 copies/mL). Stepwise Cox regression models were fitted to estimate adjusted hazard ratios (aHR) of VF.

RESULTS

Fifteen VF occurred in 13 patients over 187 person-years of follow-up (PYFU): incidence rate (IR) of 8.0 per 100-PYFU (95% CI = 4.0-12.1); 29 VBs were detected in 26 patients over 184 PYFU: IR = 15.8 per 100-PYFU (95% CI = 10.0-21.5). The most prominent factor associated with VF was the presence of BL HIV residual viremia (RV = HIV-RNA detectable but not precisely quantifiable) [aHR = 12.26 (95% CI = 3.74-40.17), P<0.0001]. Other factors were ≥1 VBs in the 6 months before DAAs [aHR = 6.95 (95% CI = 1.77-27.37) P = 0.006] number of ART regimens failed before DAAs initiation [aHR (per more regimen) = 1.22 (95% CI = 1.04-1.42), P = 0.012] and age [aHR (per year older) = 1.16 (95% CI = 1.04-1.29), P = 0.010].

CONCLUSIONS

Our findings underline the importance for close monitoring HIV-VL in selected patients. Whether this phenomenon is triggered by the rapid clearance of HCV remains to be established.

Hepatitis C Virus (HCV) Clearance After Treatment With Direct-Acting Antivirals in Human Immunodeficiency Virus (HIV)-HCV Coinfection Modulates Systemic Immune Activation and HIV Transcription on Antiretroviral Therapy

Background

Hepatitis C virus (HCV) coinfection among people with human immunodeficiency virus (HIV) might perturb immune function and HIV persistence. We aimed to evaluate the impact of HCV clearance with direct-acting antivirals (DAAs) on immune activation and HIV persistence in HIV/HCV-coinfected individuals on antiretroviral therapy (ART).

Methods

In a prospective observational study, ART-treated participants with HIV/HCV coinfection received sofosbuvir/daclatasvir ± ribavirin (n = 19). Blood samples were collected before DAA therapy, at the end of treatment, and 12 months after DAA termination (12MPT). T- and natural killer (NK)-cell phenotype, soluble plasma factors, cell-associated (CA)-HIV deoxyribonucleic acid (DNA) forms (total, integrated, 2LTR), CA-unspliced (US) and multiple-spliced ribonucleic acid (RNA), and plasma HIV RNA were evaluated.

Results

Hepatitis C virus clearance was associated with (1) a downmodulation of activation and exhaustion markers in CD4⁺, CD8⁺ T, and NK cells together with (2) decreased plasma levels of Interferon gamma-induced protein 10 (IP10), interleukin-8 (IL-8), soluble (s)CD163 and soluble intercellular adhesion molecule (sICAM). Cell-associated US HIV RNA was significantly higher at 12MPT compared to baseline, with no change in HIV DNA or plasma RNA.

Conclusions

Elimination of HCV in HIV/HCV-coinfected individuals alters immune function and the transcriptional activity of latently infected cells. This report provides insights into the effects of HCV coinfection in HIV persistence and regards coinfected subjects as a population in which HIV remission might prove to be more challenging.

Ultrasensitive Human Immunodeficiency Virus Type 1 Viral Load as a Marker of Treatment Choice for Simplification Strategies

Background

Using 3 randomized Protease inhibitor (PI) monotherapy studies: Kalesolo, Dream and Monoi, we performed a pooled-analysis. Our objective was to determine in PI monotherapy and standard tritherapy: 1) distribution of ultrasensitive viral load (USVL) at week 96 (W96); 2) factors associated with virological failure (VF) at W96 and 3) factors associated with USVL<1 copy at W96.

Methods

VF was defined as 2 consecutive measurements of Human Immunodeficiency Virus Type 1 RNA viral load>50 copies/mL and analysed in Intention-To-Treat. A logistic model was used to investigate which variables were predictive of a VF and Fisher test to investigate differences in USVL at W96.

Results

Among 609 patients, 73% were male with median age of 44.4 years (IQR 39.8-52.1), baseline CD4/CD8 ratio was 0.8 (IQR 0.6-1.10), baseline CD4 was 564.5/mm3 (IQR 422-707) and 59% presented a baseline USVL<1 copy/mL. At W96, the proportion of USVL<1 copy/mL was significantly different between PI monotherapy and standard tritherapy in pooled-analysis (65% versus 74%; p=0.04). Overall, baseline USVL<1copy/mL, tritherapy and to be a female were associated with USVL<1 copy/mL at W96 (p<0.0001, p=0.049 and p=0.006). In PI monotherapy receiving DRV/r was associated with USVL<1 copy/mL at W96 (p=0.003). Factors associated to virological succes at W96 were higher baseline CD4 (p=0.034) and baseline USVL<1 copy/mL (p=0.0005).

Conclusion

Pooled-analysis of 3 PI monotherapy trials showed better efficacy of tritherapy in terms of USVL at W96. Furthermore regarding USVL at W96, to receive LPV/r seems to be more deleterious than DRV/r. Baseline USVL impacts VF at W96 more specifically in tritherapy arm.

Clinical Trials Registration

NCT00421551, NCT00946595, and NCT00140751.

Quantification of HIV-DNA and residual viremia in patients starting ART by droplet digital PCR: Their dynamic decay and correlations with immunological parameters and virological success

BACKGROUND

Accurate quantification of total HIV-DNA and residual-viremia by sensitive assays is extremely useful to optimize monitoring of ART-treated patients.

OBJECTIVES

To evaluate the performances of two ddPCR-based assays for HIV-DNA and residual-viremia quantification, and the correlations of pre-ART HIV-DNA with plasma HIV-RNA, CD4 + T, CD4/CD8 and virological-success (VS) during first-line ART.

STUDY DESIGN

Plasma HIV-RNA, total HIV-DNA, CD4 + T, CD4/CD8 were evaluated at baseline of ART, at VS (viral-load <50copies/ml), and at 6 months after VS (6moVS) in 57 newly-diagnosed HIV-1 infected patients, receiving first-line modern ART. HIV-DNA (log10 copies/106CD4 + T) and residual-viremia (copies/ml) were measured with in-house ddPCR assays. Correlations were assessed by Spearman and Jonckheere-Terpstra tests.

RESULTS

HIV-DNA and residual-viremia assays showed a good linear trend between the expected and obtained values (R2 = 0.9913 and 0.9945); lower limits of detection were 32 copies/106CD4 + T and 2 copies/ml, respectively. At baseline, median (IQR) plasma HIV-RNA and HIV-DNA were 4.88(4.28-5.36)log10 copies/ml and 4.00(3.36-4.51) log10 copies/106CD4 + T cells. Residual-viremia was 8(2-26) and 4(2-12) copies/ml at VS and 6moVS. Pre-ART HIV-DNA positively correlated with plasma HIV-RNA at BL (Rho = 0.708, p < 0.001), and with residual-viremia at VS (Rho:0.383,p = 0.002). Notably, higher HIV-DNA correlated with longer time to achieve VS (median[IQR],weeks: 17.8[12.3-29.0] for HIV-DNA ≥4.5 vs. 7.4[4.1-8.7] for HIV-DNA<4.5, p < 0.001). Furthermore, pre-ART HIV-DNA negatively correlated with CD4 + T and CD4/CD8 at baseline, VS and 6moVS.

CONCLUSIONS

Our results support the adoption of ddPCR-based assays for both HIV-DNA and residual-viremia quantifications and corroborate that pre-ART HIV-DNA is an excellent indicator in predicting viroimmunological response and VS in patients starting ART.

Time spent with residual viraemia after virological suppression below 50 HIV-RNA copies/mL according to type of first-line antiretroviral regimen

PURPOSE

To investigate if the regimen used when starting antiretroviral therapy (ART) affects the time spent with residual viraemia (RV) after achieving <50 HIV-RNA copies/mL.

METHODS

Retrospective cohort study on patients infected with human immunodeficiency virus (HIV), followed prospectively, who started ART with a boosted protease inhibitor (PI/r)-, a non-nucleoside reverse transcriptase inhibitor (NNRTI)- or an integrase inhibitor (InSTI)-based triple regimen, or a regimen with more than three drugs. RV was defined as any detectable polymerase chain reaction (PCR) signal <50 HIV-RNA copies/mL, as assessed by kinetic PCR or Abbott real-time PCR. The percentage of time spent with RV (%RV) was calculated as the cumulative follow-up time spent with RV on the observed follow-up, and was estimated using a generalized linear model.

RESULTS

Seven hundred and seventy-one patients (33%, 32%, 30% and 5% receiving PI/r-, NNRTI-, InSTI-based triple regimens, or a regimen with more than three drugs, respectively) were included in the analysis. After a median of 2.16 (interquartile range 1.27-3.16) years of follow-up, adjusted means of %RV were 37.9% [95% confidence interval (CI) 30.3-45.4%], 23.9% (95% CI 16-31.8%), 25.3% (95% CI 17.8-32.7%) and 45.5% (95% CI 34.6-56.4%) in the PI/r, NNRTI, InSTI and more than three drugs groups, respectively; %RV was significantly higher in patients who started ART with a regimen with more than three drugs (P=0.030), and was significantly lower in patients who started ART with an NNRTI-based regimen (P<0.0001) or an InSTI-based regimen (P=0.030) than in those who started ART with a PI/r-based regimen. %RV was independently associated with pre-ART HIV-RNA (P<0.0001), time to HIV-RNA <50 copies/mL (P<0.0001), NRTI backbone (P=0.037) and baseline HIV-RNA (P<0.0001).

CONCLUSION

First-line regimens based on PIs/r or on more than three drugs are associated with a greater percentage of time spent with RV after achieving virological suppression.

Time course of cellular HIV-DNA and low-level HIV viremia in HIV-HCV co-infected patients whose HCV infection had been successfully treated with directly acting antivirals

This longitudinal study described cellular HIV-DNA changes and their correlation with HIV low-level plasma viremia (LLV) in HIV-HCV co-infected patients on successful antiretroviral and anti-HCV therapy by treatment with direct-acting antivirals (DAA). Thirty-nine patients were examined prior to the start of DAA (T0), after week 12 (T1) and 24 weeks (T2) of anti-HCV therapy. Cellular PBMC HIV-DNA was analysed as an absolute value and as the percentage of increase or decrease from T0 to T2. Patients were classified as having undetectable plasma HIV viraemia (UV) or LLV in the year before the start of anti-HCV treatment and within the T0-T2 study period. Thirty-five patients (89.7%) of the 39 subjects enrolled had the same plasma HIV viraemia control in the year before HCV treatment and in the T0-T2 interval. The HIV-DNA value at T0 and at T2 was higher in patients with LLV than in subjects with UV (p = 0.015 and p = 0.014, respectively). A similar proportion of patients with LLV and UV experienced an increase or decrease of HIV-DNA from T0 to T2. The percentage increase in HIV-DNA value (262.8%) from T0 to T2 was higher compared to the decrease (43.5%) in patients with UV (p = 0.012), and it was higher compared to the percentage increase in HIV-DNA value reported in subjects with LLV (262.8 versus 49%, p = 0.026). HIV-HCV co-infected patients experienced a multifaceted perturbation of cellular HIV-DNA levels within a 24-week period during anti-HCV treatment; the extent of the phenomenon was greater in subjects with UV. Fast HCV-RNA clearance seemed to have a greater influence on the cellular reservoir than on plasma HIV-RNA.

Viral blips were infrequent in treatment-naive adults treated with rilpivirine/emtricitabine/tenofovir DF or efavirenz/emtricitabine/tenofovir DF through 96 weeks

BACKGROUND

The clinical impact of transient episodes of HIV viraemia (viral blips) on virological failure and resistance development is not fully understood. Here we investigated the blip frequency and virological outcomes of HIV-1-infected subjects experiencing viral blips among treatment-naive subjects initiating therapy on rilpivirine (RPV)/emtricitabine (FTC)/tenofovir disoproxil fumarate (TDF) or efavirenz (EFV)/FTC/TDF through 96 weeks of treatment.

METHODS

Subjects treated with at least one dose of study drug and with at least one post-baseline HIV-1 RNA value were included in this analysis. All on-drug HIV-1 RNA data points and FDA snapshot outcome data through week 96 were utilized. A viral blip was defined as after achieving confirmed suppression (two consecutive HIV-1 RNA values <50 copies/ml), any HIV-1 RNA value ≥50 copies/ml preceded and followed by HIV-1 RNA <50 copies/ml.

RESULTS

Of the 717 subjects with confirmed suppression, 67 (9.3%) experienced ≥1 blip through week 96 with similar blip frequencies occurring in both treatment arms (10.7% RPV/FTC/TDF versus 8.0% EFV/FTC/TDF; P=0.25). A significantly higher proportion of subjects with baseline HIV-1 RNA >100,000 copies/ml experienced blips compared to subjects with baseline HIV-1 RNA ≤100,000 copies/ml and this was observed in both arms. Of 72 total blip events, 61 (85%) were low-level (50-199 copies/ml). Overall, among subjects with blips, 79% were virological successes at week 96, similar to those subjects without blips (83%; P=0.50). More subjects with blips ≥200 copies/ml experienced virological failure compared to subjects with blips <200 copies/ml (36.4% versus 7.1%; P=0.02).

CONCLUSIONS

Viral blips were infrequent and similar among subjects treated with RPV/FTC/TDF or EFV/FTC/TDF. Most blips were low-level and most subjects with blips remained virologically suppressed through week 96 without experiencing virological failure.

Detection and quantification of HIV-1 RNA with a fully automated transcription-mediated-amplification assay

BACKGROUND

Nucleic acid testing is the major method used to monitor HIV viral load. Commercial systems based on real-time PCR assays are available for high-volume centralized laboratory testing, but they are not fully automated.

OBJECTIVES AND STUDY DESIGN

We have compared the diagnostic performance of the Hologic Aptima HIV-1 Quant Dx assay (Aptima) (based on real-time TMA) on the Panther instrument, a fully-automated random access platform, to that of, the Roche Cobas Ampliprep Cobas TaqMan (CAP/CTM) HIV-1 version 2.0 (based on real-time PCR).

RESULTS

Probit analysis of replicate dilutions of NIBSC WHO International HIV-1 Standard, gave LODs of 8.6 c/ml for Aptima and 15.2 c/ml for CAP/CTM. The agreement between the assays was excellent when measuring HIV RNA in a calibrated reference (κ=0.90, p<0.001) and good when measuring clinical samples (κ=0.62, p<0.001). The correlation among the samples quantified by the two methods was very good (r=0.95, p<0.001) and the mean difference between the values obtained with the two assays was 0.02 log c/ml for B and non-B subtypes. The vast majority of results showed <0.5 log variance between the two assays (89%); only one sample showed results that differed by over 1.0 log c/ml.

CONCLUSION

The performance of the new fully automated Aptima assay is adequate for clinical monitoring of HIV-1 RNA during infections and treatment. The Aptima assay is well suited for routine laboratory use.

Dolutegravir monotherapy in HIV-infected patients with sustained viral suppression

OBJECTIVES

We reviewed the 24 week outcomes of HIV-infected patients from our hospital who had their ART switched to dolutegravir monotherapy on an individual clinical basis.

METHODS

Retrospective hospital database assessment of virally suppressed patients in whom the treating physician had switched to 50 mg of dolutegravir once daily due to one or more of the following reasons: antiretroviral-related adverse effects; comorbidities; risk of interactions; or archived resistance. Patients had ≥24 weeks of follow-up. Population, virological and immunological responses and safety and tolerability are described.

RESULTS

Thirty-three (22 on PIs, of whom 18 had ritonavir-boosted PI monotherapy) patients were identified: median (IQR) age of 56 (50-62) years, 55% women, median (IQR) of 19 (17-23) years of known HIV infection, 39% prior AIDS events, median (IQR) of 8 (4-13) years with undetectable plasma HIV-1 RNA and median (IQR) CD4 cell count of 596 (420-843) cells/mm(3). Twenty-five (76%) patients had antiretroviral-related adverse effects, 32 (97%) patients had comorbidities, 28 (85%) patients had risk of interactions and 16 (48%) patients had archived resistance. One patient with suboptimal adherence had low-level virological failure through weeks 4-24. HIV RNA genotypic resistance tests detected no integrase mutations at weeks 4 and 24, but 118R was detected in 7% of the integrated HIV DNA at 24 weeks. Patients had significant median decreases in triglycerides (-117 mg/dL), total cholesterol (-36 mg/dL), the total cholesterol/HDL cholesterol ratio (-0.7) and high-sensitivity C-reactive protein (-0.05 mg/dL) (P ≤ 0.007), although the Chronic Kidney Disease Epidemiology Collaboration equation also decreased (-7.1 mL/min) (P < 0.0001).

CONCLUSIONS

These data suggest the efficacy of dolutegravir monotherapy as a maintenance strategy to be further confirmed in randomized clinical trials.

Virological response and resistance mutations to NS3/4A inhibitors in hepatitis C virus-human immunodeficiency virus coinfection

AIM: To evaluate virological response to telaprevir or boceprevir in combination with pegylated interferon and ribavirin and resistance mutations to NS3/4A inhibitors in hepatitis C virus-human immunodeficiency virus (HCV-HIV) coinfected patients in a real life setting.

METHODS: Patients with HCV genotype 1-HIV coinfection followed in Nice University Hospital internal medicine and infectious diseases departments who initiated treatment including pegylated interferon and ribavirin (PegIFN/RBV) + telaprevir or boceprevir, according to standard treatment protocols, between August 2011 and October 2013 entered this observational study. Patient data were extracted from an electronic database (Nadis^®). Liver fibrosis was measured by elastometry (Fibroscan^®) with the following cut-off values: F0-F1: < 7.1 kPa, F2: 7.1-9.5 kPa, F3: 9.5-14.5 kPa, F4: ≥ 14.5 kPa. The proportion of patients with sustained virological response (SVR) twelve weeks after completing treatment, frequency and type of adverse events, and NS3/4A protease inhibitor mutations were described.

RESULTS: Forty-one patients were included: 13 (31.7%) patients were HCV-treatment naïve, 22 (53.7%) had advanced liver fibrosis or cirrhosis (Fibroscan stage F3 and F4); none had decompensated cirrhosis or hepatocellular carcinoma; all were receiving antiretroviral treatment, consisting for most them (83%) in either a nucleoside reverse-transcriptase inhibitor/protease inhibitor or/integrase inhibitor combination; all patients had undetectable HIV-RNA. One patient was lost to follow-up. SVR was achieved by 52.5% of patients. Five patients experienced virological failure during treatment and four relapsed. Seven discontinued treatment due to adverse events. Main adverse events included severe anemia (88%) and rash (25%). NS3/4A protease mutations were analyzed at baseline and at the time of virological failure in the 9 patients experiencing non-response, breakthrough or relapse. No baseline resistance mutation could predict resistance to HCV protease inhibitor-based treatment.

CONCLUSION: Telaprevir and boceprevir retain their place among potential treatment strategies in HIV-HCV coinfected patients including those with advanced compensated liver disease and who failed previous PegIFN/RBV therapy.

Residual viremia is preceding viral blips and persistent low-level viremia in treated HIV-1 patients

BACKGROUND

It has been suggested that low-level viremia or blips in HIV-infected patients on antiretroviral treatment are related to assay variation and/or increased sensitivity of new commercial assays. The 50-copy cut-off for virologic failure is, therefore, under debate.

METHODS

Treated patients with low-level viremia (persistent viral loads (VL) of 50-1000 copies/mL, group A, N = 16) or a blip (single detectable VL, group B, N = 77) were compared to a control group (consistently suppressed viremia since start therapy (<50 copies/mL), N = 79). Residual viremia (detectable viral RNA <50 copies/ml) in the year preceding the first VL above 50 copies/mL (T0) was determined using Roche Cobas-Amplicor v1.5 or CAP-CTM v2.0. Subsequent virologic failure (2 consecutive VLs>500 or 1 VL>1000 copies/mL that was not followed by a VL<50 copies/mL; median follow up 34 months) was assessed.

RESULTS

Significantly more patients in groups A and B had residual viremia in the year preceding T0 compared to controls (50% and 19% vs 3% respectively; p<0.001). Residual viremia was associated with development of low-level viremia or blips (OR 10.9 (95% CI 2.9-40.6)). Subsequent virologic failure was seen more often in group A (3/16) and B (2/77) than in the control group (0/79).

CONCLUSION

Residual viremia is associated with development of blips and low-level viremia. Virologic failure occurred more often in patients with low-level viremia. These results suggest that low-level viremia results from viral production/replication rather than only assay variation.

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.