HIV load testing with small samples of whole blood

The performance of hepatitis C virus (HCV) antibody point-of-care tests on oral fluid or whole blood and dried blood spot testing for HCV serology and viral load among individuals at higher risk for HCV in South Africa

BACKGROUND AND AIMS

To enhance screening and diagnosis in those at-risk of hepatitis C virus (HCV), efficient and improved sampling and testing is required. We investigated the performance of point-of-care (POC) tests and dried blood spots (DBS) for HCV antibody and HCV RNA quantification in individuals at higher risk for HCV (people who use and inject drugs, sex workers and men who have sex with men) in seven South African cities.

METHODS

Samples were screened on the OraQuick HCV POC test (471 whole blood and 218 oral fluid); 218 whole blood and DBS paired samples were evaluated on the ARCHITECT HCV antibody (Abbott) and HCV viral load (COBAS Ampliprep/COBAS TaqMan version 2) assays. For HCV RNA quantification, 107 dB were analyzed with and without normalization coefficients.

RESULTS

POC on either whole blood or oral fluid showed an overall sensitivity of 98.5% (95% CI 97.4-99.5), specificity of 98.2% (95% CI 98.8-100) and accuracy of 98.4% (95% CI 96.5-99.3). On the antibody immunoassay, DBS showed a sensitivity of 96.0% (95% CI 93.4-98.6), specificity of 97% (95% CI 94.8-99.3) and accuracy of 96.3% (95% CI 93.8-98.8). A strong correlation (R 2 = 0.90) between viral load measurements for DBS and plasma samples was observed. After normalization, DBS viral load results showed an improved bias from 0.5 to 0.16 log10 IU/mL.

CONCLUSION

The POC test performed sufficiently well to be used for HCV screening in at-risk populations. DBS for diagnosis and quantification was accurate and should be considered as an alternative sample to test. POC and DBS can help scale up hepatitis services in the country, in light of our elimination goals.

Evaluation of the Xpert HBV Viral Load for hepatitis B virus molecular testing

BACKGROUND

Accurate molecular methods to detect and quantify hepatitis B virus (HBV) DNA are essential to diagnose chronic infections, guide treatment decisions, assess response to treatment, and determine risk of HBV-related complications. New HBV DNA generations of real-time assay platforms are now available with the availability of results in less than 2-3 h and a continuous loading of specimens with true random access.

OBJECTIVES

The aim of this prospective study was to evaluate the performance of the new Xpert HBV Viral Load assay to accurately quantify HBV DNA in plasma and in whole blood collected on dried blood spot (DBS).

METHODS

Plasma and whole blood from 143 patients chronically infected with HBV were tested in parallel using two commercially real-time PCR assay (Cobas AmpliPrep/Cobas Taqman HBV test, version 2.0, and Xpert HBV Viral Load assay).

RESULTS

HBV DNA levels in whole blood strongly correlated with those measured in plasma. A positive significant correlation between the HBV DNA levels in plasma measured with the new Xpert HBV Viral Load and CAP/CTM HBV v2.0 assays was found.

CONCLUSIONS

The newly developed real-time PCR-based assay Xpert HBV Viral Load accurately quantifies HBV DNA in whole blood specimens as well as in plasma samples from patients with chronic HBV infection. Whole blood specimens collected on DBS can be confidently used for replicative HBV infection detection in patients with HBV DNA level above 3 Log using standardized, commercially available methods.

Impact of Early Antiretroviral Therapy on Detection of Cell-Associated HIV-1 Nucleic Acid in Blood by the Roche Cobas TaqMan Test

The Roche Cobas AmpliPrep/Cobas TaqMan HIV-1 test, v2.0 (the CAP/CTM assay), was used to quantify cell-associated HIV-1 (CAH) nucleic acid in peripheral blood mononuclear cells (PBMC) from well-characterized clinical specimens from HIV-1-infected individuals on antiretroviral therapy (ART). Chronically infected individuals on ART with no detectable plasma HIV-1 RNA demonstrated average CAH burdens of 3.2 HIV-1 log10 copies/million cells. Assay sensitivity and specificity were 98.9% and 100%, respectively, with the positive and negative predictive values being 100% and 98.6%, respectively. The CAH burden was also measured at weeks 0, 1, 2, 8, and 60 in 37 participants (RV254/SEARCH010, Bangkok, Thailand) stratified by Fiebig stage (Fiebig stage I [FI] to FVI) at ART initiation. Prior to ART initiation, the average CAH burden was 1.4, 4.1, and 3.6 log10 copies/million PBMCs for individuals who initiated ART at FI, FII, and FIII to FVI, respectively. Initiation of ART resulted in a rapid decline of CAH in all individuals, with the greatest decrease being observed in individuals who initiated ART at FI to FIII. By week 60, 100% (FI), 71.8% (FII/FIII), and 20.5% (FIV to FVI) of samples from individuals initiating treatment were at or near the limit of quantitation. Residual CAH was detectable at 60 weeks in most individuals who initiated ART at later stages (FIV to FVI) and averaged 1.9 ± 0.7 log10 copies/million PBMCs. The modified Roche CAP/CTM assay provides a convenient, standardized approach to measure residual HIV in blood and may be useful for monitoring patients under therapy or those participating in HIV remission studies.

Diagnosis of Human Immunodeficiency Virus Infection

HIV diagnostics have played a central role in the remarkable progress in identifying, staging, initiating, and monitoring infected individuals on life-saving antiretroviral therapy. They are also useful in surveillance and outbreak responses, allowing for assessment of disease burden and identification of vulnerable populations and transmission "hot spots," thus enabling planning, appropriate interventions, and allocation of appropriate funding. HIV diagnostics are critical in achieving epidemic control and require a hybrid of conventional laboratory-based diagnostic tests and new technologies, including point-of-care (POC) testing, to expand coverage, increase access, and positively impact patient management. In this review, we provide (i) a historical perspective on the evolution of HIV diagnostics (serologic and molecular) and their interplay with WHO normative guidelines, (ii) a description of the role of conventional and POC testing within the tiered laboratory diagnostic network, (iii) information on the evaluations and selection of appropriate diagnostics, (iv) a description of the quality management systems needed to ensure reliability of testing, and (v) strategies to increase access while reducing the time to return results to patients. Maintaining the central role of HIV diagnostics in programs requires periodic monitoring and optimization with quality assurance in order to inform adjustments or alignment to achieve epidemic control.

Dried Blood Spots for Global Health Diagnostics and Surveillance: Opportunities and Challenges

There is increasing interest in using dried blood spot (DBS) cards to extend the reach of global health and disease surveillance programs to hard-to-reach populations. Conceptually, DBS offers a cost-effective solution for multiple use cases by simplifying logistics for collecting, preserving, and transporting blood specimens in settings with minimal infrastructure. This review describes methods to determine both the reliability of DBS-based bioanalysis for a defined use case and the optimal conditions that minimize pre-analytical sources of data variability. Examples by the newborn screening, drug development, and global health communities are provided in this review of published literature. Sources of variability are linked in most cases, emphasizing the importance of field-to-laboratory standard operating procedures that are evidence based and consider both stability and efficiency of recovery for a specified analyte in defining the type of DBS card, accessories, handling procedures, and storage conditions. Also included in this review are reports where DBS was determined to not be feasible because of technology limitations or physiological properties of a targeted analyte.

Fast, Sensitive, and Quantitative Point-of-Care Platform for the Assessment of Drugs of Abuse in Urine, Serum, and Whole Blood

Drug abuse is a major public health problem in many countries in Europe and North America. Currently available platforms for drug abuse assessment are facing technical challenges of nonquantitation, inaccuracy, low throughput, incompatibility with diverse complex specimens, long assay times, and requirement of instrument and/or expertise for readout. Here, we report an integrated competitive volumetric-bar-chart chip (CV-Chip) to assay multiple drug targets at the point-of-care (POC). To the best of our knowledge, it is the first time that a POC platform has been demonstrated to fully address the above-mentioned limitations. We applied this integrated CV-chip platform to assay multiple drugs in 38 patient urine and serum samples and validated the on-chip results with an LC-MS/MS method, indicating a clinical sensitivity and specificity of 0.94 and 1.00, respectively. We further demonstrated that the combination of an on-chip blood separator with the CV-Chip enabled the platform to directly assay finger-prick whole blood samples, which have always been recognized as an ideal biospecimen for POC detections. In summary, this integrated CV-Chip is able to serve as a sensitive, accurate, fast, portable, readout visible, and minimally invasive platform for drug abuse assessment.

Dried Blood Spots: A Tool to Ensure Broad Access to Hepatitis C Screening, Diagnosis, and Treatment Monitoring

BACKGROUND

With the advent of highly efficient antiviral therapies for hepatitis C virus (HCV) infection, providing broad access to diagnosis and care is needed. The dried blood spot (DBS) technique can be used to collect, store, and ship whole-blood specimens. Our goal was to assess the performance of standardized HCV diagnostic and monitoring tools in the analysis of DBS.

METHODS

Serum specimens and whole-blood specimens collected using the DBS technique from >500 patients were tested for virological markers used to diagnose and monitor HCV infection.

RESULTS

Enzyme immunoassay detection of anti-HCV antibodies in specimens from DBS was reliable after establishment of a new signal-to-cutoff ratio. HCV RNA was detected DBS from the vast majority of patients with active replication, but HCV RNA levels were substantially lower than in serum specimens, implying that only the presence or absence of HCV RNA or changes in the HCV RNA level should be taken into consideration for therapy. Detection of HCV core antigen in specimens from DBS was not a sensitive marker of chronic HCV infection. HCV genotype determination was possible in the vast majority of DBS.

CONCLUSIONS

This study shows that whole-blood specimens collected using the DBS technique can be confidently used to diagnose and monitor HCV infection. DBS could help improve access to care for HCV infection because they are suitable for use in large-scale screening programs, diagnosis, and therapeutic monitoring.

HIV-1 variability and viral load technique could lead to false positive HIV-1 detection and to erroneous viral quantification in infected specimens

OBJECTIVES

Viral load (VL) testing is used for early HIV diagnosis in infants (EID) and for detecting early therapeutic failure events, but can be affected by HIV genetic variability. Dried blood samples (DBS) increase VL access and EID in remote settings and when low blood volume is available.

METHODS

This study compares VL values using Siemens VERSANT HIV-1 RNA 1.0 kPCR assay (kPCR) and Roche CAP/CTM Quantitative test v2.0 (CAP/CTM v2.0) in 176 DBS carrying different HIV-1 variants collected from 69 Equatoguinean mothers and their infants with known HIV-1 status (71 infected, 105 uninfected).

RESULTS

CAP/CTM v2.0 provided false positive VLs in 11 (10.5%) cases. VL differences above 0.5 log10 were observed in 42/49 (87.5%) DBS, and were above 1 log10 in 18 cases. CAP/CTM v2.0 quantified all the 41 specimens with previously inferred HIV-1 variant by phylogenetic analysis (68.3% recombinants) whereas kPCR only identified 90.2% of them, and was unable to detect 14.3% of 21 CRF02_AG viruses. CAP/CTM v2.0 showed higher sensitivity than kPCR (95.8% vs. 70.1%), quantifying a higher rate of viruses in infected DBS from subjects under antiretroviral exposure at sampling time compared to kPCR (94.7% vs. 96.2%, p-value<0.001). kPCR showed maximum specificity (100%) whereas for CAP/CTM v2.0 was 89.5%.

CONCLUSIONS

VL assays should increase their sensitivity and specificity to avoid overestimated HIV-1 quantifications, which could be interpreted as virological failure events, or false negative diagnostic results due to genetic variability. We recommend using the same VL technique for each patient during antiretroviral therapy monitoring.

Leukodepletion as a point-of-care method for monitoring HIV-1 viral load in whole blood

In order to limit the interference of HIV-1 cellular nucleic acids in estimating viral load (VL), the feasibility of leukodepletion of a small whole-blood (WB) volume to eliminate only leukocyte cell content was investigated, using a selection of filters. The efficacy of leukocyte filtration was evaluated by counting, CD45 quantitative PCR, and HIV-1 DNA quantification. Plasma HIV-1 was tested by real-time reverse transcription (RT)-PCR. A specific, miniaturized filter was developed and tested for leukocyte and plasma virus retention, WB sample dilution, and filtration parameters in HIV-1-spiked WB samples. This device proved effective to retain >99.9% of white blood cells in 100 μl of WB without affecting plasma VL. The Samba sample preparation chemistry was adapted to use a leukodepleted WB sample for VL monitoring using the point-of-care Samba-1 semiautomated system. The clinical performance of the assay was evaluated by testing 207 consecutive venous EDTA WB samples from HIV-1-infected patients attending a CD4 testing clinic. Most patients were on antiretroviral treatment (ART), but their VL status was unknown. Compared to the Roche Cobas AmpliPrep/Cobas TaqMan HIV-1 test, the new Samba assay had a concordance of 96.5%. The use of the Samba system with a VL test for WB might contribute to HIV-1 ART management and reduce loss-to-follow-up rates in resource-limited settings.

Evaluation of quantification of HIV-1 RNA viral load in plasma and dried blood spots by use of the semiautomated Cobas Amplicor assay and the fully automated Cobas Ampliprep/TaqMan assay, version 2.0, in Kisumu, Kenya

In Kenya, HIV-1 viral load monitoring is commonly performed with the Cobas Amplicor using plasma specimens. Interest is growing in transitioning to real-time PCR (RT-PCR), such as the Cobas Ampliprep/Cobas TaqMan (CAP/CTM), using dried blood spots (DBS). Before implementation, direct evaluation of the two assays using DBS field specimens is required. This study compares the sensitivity, specificity, negative and positive predictive values (NPV and PPV, respectively), concordance, and agreement between HIV-1 viral load measurements using plasma and DBS specimens obtained from 512 HIV-1-infected pregnant females enrolled in the Kisumu Breastfeeding Study and tested with the Cobas Amplicor and CAP/CTM assays. The sensitivity and NPV of viral load detection in DBS specimens were higher with CAP/CTM (sensitivity, 100%; 95% confidence interval [CI], 99.1 to 100.0%; NPV, 100%; 95% CI, 59.0 to 100.0%) than the Cobas Amplicor (sensitivity, 96.6%; 95% CI, 94.3 to 98.1%; NPV, 58.8%; 95% CI, 40.7 to 75.4%). The PPVs were comparable between both assays when using DBS. The specificity of viral load detection in DBS specimens was lower with CAP/CTM (77.8%; 95% CI, 40.0 to 97.2%) than that of the Cobas Amplicor (95.2%; 95% CI, 76.2 to 99.9%). Good concordance and agreement were observed when paired plasma and DBS specimens were tested with both assays. Lower specificity with the CAP/CTM is likely due to proviral HIV-1 DNA amplification and lower detection limits with RT-PCR. However, the CAP/CTM has better sensitivity and higher throughput than the Cobas Amplicor. These findings suggest that DBS may be a suitable alternative to plasma when using RT-PCR, which could increase access to viral load monitoring in resource-limited settings.

Guidelines for the quantification of HIV and HCV in small volume whole blood samples

The quantification of Hepatitis C Virus (HCV) and Human Immunodeficiency Virus (HIV) in whole blood provides several advantages over the quantification in plasma samples. The application of small samples of capillary blood allows for application in point-of-care diagnostic testing methods.Here we describe two protocols of extracting viral RNA from small samples of whole blood by hybridization to biotinylated LNA-modified 2'-O-Methyl-RNA or to biotinylated DNA, indirect capturing to streptavidin-coated beads, and subsequent quantification by one-step non-nested qRT-PCR. Further, we provide some general guidelines on extraction and quantification of HIV and HCV in small volume whole blood samples.

Using HIV viral load to guide treatment-for-prevention interventions

PURPOSE OF REVIEW

To provide evidence that HIV-1 RNA load can guide treatment-for-prevention interventions to mitigate the HIV epidemic.

RECENT FINDINGS

Some HIV-infected individuals maintain increased levels of HIV-1 RNA load after acute infection for an extended period of time, and can disproportionately contribute to the spread of HIV in the community. The recent HIV Prevention Trials Network 052 study has demonstrated 96% efficacy for initiation of early antiretroviral treatment (ART) in HIV-1 serodiscordant couples.

SUMMARY

The level of HIV-1 RNA load in plasma is the major biological predictor of virus transmission. HIV-infected individuals who maintain increased levels of HIV-1 RNA load, extended high viremics, can transmit virus at higher rates. Combinatorial ART decreases HIV replication, thus reducing rates of virus transmission. Identifying high viremics and placing them on ART seems an attractive strategy that has the potential to achieve both individual benefits by lowering risk for early onset of clinical AIDS and public health benefits by reducing HIV transmission. A key logistical challenge is to screen for high viremics among HIV-positive individuals. Efficacy of the modified treatment-for-prevention approach focused on high viremics is being evaluated in ongoing and upcoming clinical trials. If efficacious, such an approach could be used widely to mitigate and control the HIV epidemic.

Comparison of HIV-1 detection in plasma specimens and dried blood spots using the Roche COBAS Ampliscreen HIV-1 test in Kisumu, Kenya

The World Health Organization recommends screening donor blood for HIV in centralized laboratories. This recommendation contributes to quality, but presents specimen transport challenges for resource-limited settings which may be relieved by using dried blood spots (DBS). In sub-Saharan Africa, most countries screen donor blood with serologic assays only. Interest in window period reduction has led blood services to consider adding HIV nucleic acid testing (NAT). The U.S. Food and Drug Administration (FDA) mandates that HIV-1 NAT blood screening assays have a 95% detection limit at or below 100 copies/ml and 5000 copies/ml for pooled and individual donations, respectively. The Roche COBAS Ampliscreen HIV-1 test, version 1.5, used for screening whole blood or components for transfusion, has not been tested with DBS. We compared COBAS Ampliscreen HIV-1 RNA detection limits in DBS and plasma. An AIDS Clinical Trials Group, Viral Quality Assurance laboratory HIV-1 standard with a known viral load was used to create paired plasma and DBS standard nine member dilution series. Each was tested in 24 replicates with the COBAS Ampliscreen. A probit analysis was conducted to calculate 95% detection limits for plasma and DBS, which were 23.8 copies/ml (95% CI 15.1-51.0) for plasma and 106.7 copies/ml (95% CI 73.8-207.9) for DBS. The COBAS Ampliscreen detection threshold with DBS suggests acceptability for individual donations, but optimization may be required for pooled specimens.