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

Sensitive and Quantitative Point-of-Care HIV Viral Load Quantification from Blood Using a Power-Free Plasma Separation and Portable Magnetofluidic Polymerase Chain Reaction Instrument

Point-of-care (POC) HIV viral load (VL) tests are needed to enhance access to HIV VL testing in low- and middle-income countries (LMICs) and to enable HIV VL self-testing at home, which in turn have the potential to enhance the global management of the disease. While methods based on real-time reverse transcription-polymerase chain reaction (RT-PCR) are highly sensitive and quantitatively accurate, they often require bulky and expensive instruments, making applications at the POC challenging. On the other hand, although methods based on isothermal amplification techniques could be performed using low-cost instruments, they have shown limited quantitative accuracies, i.e., being only semiquantitative. Herein, we present a sensitive and quantitative POC HIV VL quantification method from blood that can be performed using a small power-free three-dimensional-printed plasma separation device and a portable, low-cost magnetofluidic real-time RT-PCR instrument. The plasma separation device, which is composed of a plasma separation membrane and an absorbent material, demonstrated 96% plasma separation efficiency per 100 μL of whole blood. The plasma solution was then processed in a magnetofluidic cartridge for automated HIV RNA extraction and quantification using the portable instrument, which completed 50 cycles of PCR in 15 min. Using the method, we achieved a limit of detection of 500 HIV RNA copies/mL, which is below the World Health Organization's virological failure threshold, and a good quantitative accuracy. The method has the potential for sensitive and quantitative HIV VL testing at the POC and at home self-testing.

Evaluation of SAMBA II: A Qualitative and Semiquantitative HIV Point-of-Care Nucleic Acid Test

BACKGROUND

Point-of-care (POC) nucleic acid tests (NATs) have potential to diagnose acute HIV infection and monitor persons taking pre-exposure prophylaxis or antiretroviral therapy (ART). POC NATs have not yet been evaluated in the US.

METHODS

From June 2018-March 2019, we conducted a cross-sectional evaluation of the Simple Amplification-Based Assay version II (SAMBA II) POC NAT. People with HIV (PWH) and persons testing for HIV were tested with the SAMBA II qualitative (Qual) whole blood (WB) test. From April-September 2019, the Qual test was used on persons who were ART-naive, and SAMBA II Semi-quantitative (Semi-Q) WB was used with ART-experienced PWH. Both were performed on unprocessed venipuncture (VP) and, when indicated by protocol, fingerstick (FS) WB and plasma. SAMBA results were compared with Abbott RealTime HIV-1 polymerase chain reaction results on plasma. We calculated sensitivity, specificity, and concordance between tests.

RESULTS

SAMBA was used in 330 visits among 280 participants: 202 (61.2%) visits from PWH, and 128 (38.8%) from HIV-negative persons. Qual test sensitivity with ART-naive participants was 91.4% [32/35, 95% confidence interval (CI): 77.6% to 97.0%] using VP WB and 100% (27/27, 95% CI: 87.5% to 100%) using FS WB. Specificity was 100% using both specimen types. Concordance between the gold standard and Semi-Q at 1000 copies/mL among PWH on ART was 97.7% (86/88, 95% CI: 92.1% to 99.4%) and 100% (30/30, 95% CI: 88.7% to 100%) using VP and FS WB, respectively.

CONCLUSIONS

The SAMBA II POC NATs showed high sensitivity, specificity, and concordance with the gold standard assay, indicating its potential use in diagnostics and monitoring. Future work will evaluate POC NAT implementation in the US.

Point-of-care viral load tests to detect high HIV viral load in people living with HIV/AIDS attending health facilities

BACKGROUND

Viral load (VL) testing in people living with HIV (PLHIV) helps to monitor antiretroviral therapy (ART). VL is still largely tested using central laboratory-based platforms, which have long test turnaround times and involve sophisticated equipment. VL tests with point-of-care (POC) platforms capable of being used near the patient are potentially easy to use, give quick results, are cost-effective, and could replace central or reference VL testing platforms.

OBJECTIVES

To estimate the diagnostic accuracy of POC tests to detect high viral load levels in PLHIV attending healthcare facilities.

SEARCH METHODS

We searched eight electronic databases using standard, extensive Cochrane search methods, and did not use any language, document type, or publication status limitations. We also searched the reference lists of included studies and relevant systematic reviews, and consulted an expert in the field from the World Health Organization (WHO) HIV Department for potentially relevant studies. The latest search was 23 November 2020.

SELECTION CRITERIA

We included any primary study that compared the results of a VL test with a POC platform to that of a central laboratory-based reference test to detect high viral load in PLHIV on HIV/AIDS care or follow-up. We included all forms of POC tests for VL as defined by study authors, regardless of the healthcare facility in which the test was conducted. We excluded diagnostic case-control studies with healthy controls and studies that did not provide sufficient data to create the 2 × 2 tables to calculate sensitivity and specificity. We did not limit our study inclusion to age, gender, or geographical setting.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles, abstracts, and full texts of the search results to identify eligible articles. They also independently extracted data using a standardized data extraction form and conducted risk of bias assessment using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool. Using participants as the unit of analysis, we fitted simplified univariable models for sensitivity and specificity separately, employing a random-effects model to estimate the summary sensitivity and specificity at the current and commonly reported World Health Organization (WHO) threshold (≥ 1000 copies/mL). The bivariate models did not converge to give a model estimate.

MAIN RESULTS

We identified 18 studies (24 evaluations, 10,034 participants) defining high viral loads at main thresholds ≥ 1000 copies/mL (n = 20), ≥ 5000 copies/mL (n = 1), and ≥ 40 copies/mL (n = 3). All evaluations were done on samples from PLHIV retrieved from routine HIV/AIDS care centres or health facilities. For clinical applicability, we included 14 studies (20 evaluations, 8659 participants) assessing high viral load at the clinical threshold of ≥ 1000 copies/mL in the meta-analyses. Of these, sub-Saharan Africa, Europe, and Asia contributed 16, three, and one evaluation respectively. All included participants were on ART in only nine evaluations; in the other 11 evaluations the proportion of participants on ART was either partial or not clearly stated. Thirteen evaluations included adults only (n = 13), five mixed populations of adults and children, whilst in the remaining two the age of included populations was not clearly stated. The majority of evaluations included commercially available tests (n = 18). Ten evaluations were POC VL tests conducted near the patient in a peripheral or onsite laboratory, whilst the other 10 were evaluations of POC VL tests in a central or reference laboratory setting. The test types evaluated as POC VL tests included Xpert HIV-1 Viral Load test (n = 8), SAMBA HIV-1 Semi-Q Test (n = 9), Alere Q NAT prototype assay for HIV-1 (n = 2) and m-PIMA HIV-1/2 Viral Load test (n = 1). The majority of evaluations (n = 17) used plasma samples, whilst the rest (n = 3) utilized whole blood samples. Pooled sensitivity (95% confidence interval (CI)) of POC VL at a threshold of ≥ 1000 copies/mL was 96.6% (94.8 to 97.8) (20 evaluations, 2522 participants), and pooled specificity (95% CI) was 95.7% (90.8 to 98.0) (20 evaluations, 6137 participants). Median prevalence for high viral load (≥ 1000 copies/mL) (n = 20) was 33.4% (range 6.9% to 88.5%). Limitations The risk of bias was mostly assessed as unclear across the four domains due to incomplete reporting.

AUTHORS' CONCLUSIONS

We found POC VL to have high sensitivity and high specificity for the diagnosis of high HIV viral load in PLHIV attending healthcare facilities at a clinical threshold of ≥ 1000 copies/mL.

Study To Evaluate the Performance of a Point-of-Care Whole-Blood HIV Viral Load Test (SAMBA II HIV-1 Semi-Q Whole Blood)

Remote areas of many low and middle income (LMI) countries have poor access to HIV viral load (HIV VL) testing. The SAMBA II (simple amplification-based assay) Semi-Q whole-blood test (Diagnostics for the Real World [DRW], Cambridge, UK) is a point-of-care assay, which uses leucodepletion technology to allow whole-blood testing in remote settings. A total of 1,540 consecutive HIV-positive clinic patients in Cameroon (250), United Kingdom (633), Ukraine (412), and Zimbabwe (245) donated venous blood (all countries) and finger prick blood (all except UK) for testing on SAMBA II. SAMBA II results were compared with simultaneous plasma results on the Abbott RealTime HIV-1 (Abbott Molecular, Des Plaines, IL) viral load assay and interpreted as either <1,000 RNA copies/ml or ≥1,000 RNA copies/ml. For 1,528 venous whole-blood samples tested on SAMBA II, overall percent agreement with the reference test at a cutoff HIV VL of ≥1,000 copies/ml was 96.9% (1,480/1,528; 95% confidence interval [CI], 95.9% to 97.7%), negative percent agreement was 97.7% (1,259/1,289; 95% CI, 96.7% to 98.4%), and positive percent agreement was 92.5% (221/239; 95% CI, 88.4% to 95.5%). For 854 finger prick samples, there was 95.0% (811/854; 95% CI, 93.3% to 96.3%) overall percent agreement, 98.0% (625/638; 95% CI, 96.5% to 98.9%) negative percent agreement, and 86.1% (186/216; 95% CI, 80.8% to 90.4%) positive percent agreement. These rose to 93.5% (82.1% to 98.6%), 97.6% (95.6% to 98.8%), and 95.6% (93.3% to 97.3%) after exclusion of aberrant results from the Ukraine center. These results show a high level of agreement between SAMBA-II and a laboratory-based assay. SAMBA-II has a performance that is suitable to use as a VL point-of-care assay in remote settings.

Performance Evaluation of the SAMBA II SARS-CoV-2 Test for Point-of-Care Detection of SARS-CoV-2

Nucleic acid amplification for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA in respiratory samples is the standard method for diagnosis. The majority of this testing is centralized and therefore has turnaround times of several days. Point-of-care (POC) testing with rapid turnaround times would allow more effective triage in settings where patient management and infection control decisions need to be made rapidly. The inclusivity and specificity of the Simple AMplification-Based Assay (SAMBA) II SARS-CoV-2 test were determined by both in silico analyses of the primers and probes and wet testing. The SAMBA II SARS-CoV-2 test was evaluated for performance characteristics. Clinical performance was evaluated in residual combined throat/nose swabs and compared to that of the Public Health England real-time PCR assay targeting the RdRp gene. The SAMBA II SARS-CoV-2 test has an analytical sensitivity of 250 copies/ml for detecting two regions of the genome (open reading frame 1ab [ORF1ab] and nucleocapsid protein [N]). The clinical performance was evaluated in 172 residual combined nose/throat swabs provided by the Clinical Microbiology and Public Health Laboratory, Addenbrooke's Hospital, Cambridge (CMPHL), which showed an estimated positive percent agreement of 98.9% (95% confidence interval [CI], 93.83 to 99.97) and negative percent agreement of 96.4% (95% CI, 89.92 to 99.26) compared to testing by the CMPHL. The data show that the SAMBA II SARS-CoV-2 test performs equivalently to the centralized testing methods, but with a shorter turnaround time of 86 to 101 min. Point-of-care tests such as SAMBA should enable rapid patient management and effective implementation of infection control measures.

Extracellular vesicles from plasma have higher tumour RNA fraction than platelets

In addition to Circulating Tumour Cells (CTCs), cell-free DNA (cfDNA) and Extracellular Vesicles (EVs), the notion of “Tumour-Educated Platelets” (TEP) has recently emerged as a potential source of tumour-derived biomarkers accessible through blood liquid biopsies. Here we sought to confirm the suitability of the platelet blood fraction for biomarker detection in comparison to their corresponding EV fraction. As publications have claimed that tumour RNA and other tumour-derived material are transferred from tumour cells to the platelets and that tumour-derived transcripts can be detected in platelets, we chose to focus on RNA carrying a mutation as being of bona fide tumour origin. After informed consent, we collected prospective blood samples from a cohort of 12 melanoma patients with tissue-confirmed BRAF V600E mutation. Each blood specimen was processed immediately post collection applying two published standard protocols in parallel selecting for EVs and platelets, respectively. The RNA of each fraction was analysed by a highly sensitive ARMS RT-qPCR enabling the quantification of the mutant allele fraction (%MAF) of BRAF V600E down to 0.01%. In a direct comparative analysis, the EV fraction contained detectable BRAF V600E in 10 out of 12 patients, whereas none of the patient platelet fractions resulted in a mutant allele signal. The platelet fraction of all 12 patients contained high amounts of wild-type BRAF signal, but no mutation signal above background was detectable in any of the samples. Our observations suggest that the phenomenon of tumour RNA transfer to platelets occurs below detection limit since even a very sensitive qPCR assay did not allow for a reliable detection of BRAF V600E in the platelet fraction. In contrast, EV fractions derived from the same patients allowed for detection of BRAF V600E in 10 of 12 blood specimens.

Systematic review of the performance and clinical utility of point of care HIV-1 RNA testing for diagnosis and care

BACKGROUND

Point of-care (POC) HIV-1 RNA tests which are accurate and easy to use with limited infrastructure are needed in resource-limited settings (RLS). We systematically reviewed evidence of POC test performance compared to laboratory-based HIV-1 RNA assays and the potential utility of these tests for diagnosis and care in RLS.

METHODS

Studies published up to July 2018 were identified by a search of PUBMED, EMBASE, Web of Science, CINAHL and Cochrane Central Register of Controlled Trials. Studies evaluating the use of POC HIV-1 RNA testing for early infant diagnosis (EID), acute HIV infection (AHI) diagnosis, or viral load monitoring (VL), compared to centralized testing, were included. Separate search strategies were used for each testing objective.

RESULTS

197 abstracts were screened and 34 full-text articles were assessed, of which 32 met inclusion criteria. Thirty studies evaluated performance and diagnostic accuracy of POC tests compared to standard reference tests. Two of the thirty and two additional studies with no comparative testing reported on clinical utility of POC results. Five different POC tests (Cepheid GeneXpert HIV-1 Quantitative and Qualitative assays, Alere q HIV-1/2 Detect, SAMBA, Liat HIV Quant and Aptima HIV-1 Quant) were used in 21 studies of VL, 11 of EID and 2 of AHI. POC tests were easy to use, had rapid turnaround times, and comparable accuracy and precision to reference technologies. Sensitivity and specificity were high for EID and AHI but lower for VL. For VL, lower sensitivity was reported for whole blood and dried blood spots compared to plasma samples. Reported error rates for Cepheid GeneXpert Qual (2.0%-5.0%), GeneXpert Quant (2.5%-17.0%) and Alere q HIV-1/2 Detect (3.1%-11.0%) were higher than in WHO prequalification reports. Most errors resolved with retesting; however, inadequate sample volumes often precluded repeat testing. Only two studies used POC results for clinical management, one for EID and another for VL. POC EID resulted in shorter time-to-result, rapid ART initiation, and better retention in care compared to centralised testing.

CONCLUSIONS

Performance of POC HIV-1 RNA tests is comparable to reference assays, and have potential to improve patient outcomes. Additional studies on implementation in limited-resources settings are needed.

Point-of-Care HIV Viral Load Testing: an Essential Tool for a Sustainable Global HIV/AIDS Response

The global public health community has set ambitious treatment targets to end the HIV/AIDS pandemic. With the notable absence of a cure, the goal of HIV treatment is to achieve sustained suppression of an HIV viral load, which allows for immunological recovery and reduces the risk of onward HIV transmission. Monitoring HIV viral load in people living with HIV is therefore central to maintaining effective individual antiretroviral therapy as well as monitoring progress toward achieving population targets for viral suppression. The capacity for laboratory-based HIV viral load testing has increased rapidly in low- and middle-income countries, but implementation of universal viral load monitoring is still hindered by several barriers and delays. New devices for point-of-care HIV viral load testing may be used near patients to improve HIV management by reducing the turnaround time for clinical test results. The implementation of near-patient testing using these new and emerging technologies may be an essential tool for ensuring a sustainable response that will ultimately enable an end to the HIV/AIDS pandemic. In this report, we review the current and emerging technology, the evidence for decentralized viral load monitoring by non-laboratory health care workers, and the additional considerations for expanding point-of-care HIV viral load testing.

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.

Evaluation of the performance of Abbott m2000 and Roche COBAS Ampliprep/COBAS Taqman assays for HIV-1 viral load determination using dried blood spots and dried plasma spots in Kenya

BACKGROUND

Routine HIV viral load testing is not widely accessible in most resource-limited settings, including Kenya. To increase access to viral load testing, alternative sample types like dried blood spots (DBS), which overcome the logistic barriers associated with plasma separation and cold chain shipment need to be considered and evaluated. The current study evaluated matched dried blood spots (DBS) and dried plasma spots (DPS) against plasma using the Abbott M 2000 (Abbott) and Roche Cobas Ampliprep/Cobas TaqMan (CAP/CTM) quantitative viral load assays in western Kenya.

METHODS

Matched plasma DBS and DPS were obtained from 200 HIV-1 infected antiretroviral treatment (ART)-experienced patients attending patient support centers in Western Kenya. Standard quantitative assay performance parameters with accompanying 95% confidence intervals (CI) were assessed at the assays lower detection limit (400cps/ml for CAP/CTM and 550cps/ml for Abbott) using SAS version 9.2. Receiver operating curves (ROC) were further used to assess viral-load thresholds with best assay performance (reference assay CAP/CTM plasma).

RESULTS

Using the Abbott test, the sensitivity and specificity, respectively, for DPS were (97.3%, [95%CI: 93.2-99.2] and 98.1% [95%CI: 89.7-100]) and those for DBS (93.9% [95%CI: 88.8-97.2] and 88.0% [95%CI: 82.2-92.4]). The correlation and agreement using paired plasma and DPS/DBS were strong, with r2 = 90.5 and rc = 68.1. The Bland-Altman relative percent change was 95.3 for DPS, (95%CI: 90.4-97.7) and 73.6 (95%CI: 51.6-86.5) for DBS. Using the CAP/CTM assay, the sensitivity for DBS was significantly higher compared to DPS (100.0% [95% CI: 97.6-100.0] vs. 94.7% [95%CI: 89.8-97.7]), while the specificity for DBS was lower: 4%, [95% CI: 0.4-13.7] compared to DPS: 94.0%, [95% CI: 83.5-98.7]. When compared under different clinical relevant thresholds, the accuracy for the Abbott assay was 95% at the 1000cps/ml cut-off with a sensitivity and specificity of 96.6% [95% CI 91.8-98.7] and 90.4% [95% CI 78.2-96.4] respectively. The optimum threshold was at 3000 cps/ml with an accuracy of 95.5%, sensitivity and specificity of 94.6% [95%CI 89.3-97.5] and 98.1% [95%CI 88.4-99.9]) respectively. The best threshold for CAP/CTM was at 4000 copies /mL, with 92.5% accuracy (sensitivity of 96.0% [95%CI 91.0-98.3] and specificity of 82.7% [95%CI 69.2-91.3]).

CONCLUSIONS

There was similar performance between matched DBS, DPS and plasma using the Abbott test, and good correlation for matched DPS and plasma using the CAPCTM test. The findings suggest that DBS and DPS may be reliably used as alternative specimens to plasma to measure HIV-1 VL using Abbott, and DPS may be reliably used with CAP/CTM in resource-limited settings.

Performance of the SAMBA I and II HIV-1 Semi-Q Tests for viral load monitoring at the point-of-care

Although access to antiretroviral therapy for HIV infection is increasing in resource-poor countries, viral load testing for monitoring of treatment efficacy remains limited, expensive, and confined to centralized laboratories. The SAMBA HIV-1 Semi-Q Test is a nucleic acid-based amplification assay developed for viral load monitoring performed on either the semi-automated SAMBA I system for laboratory use or the fully automated SAMBA II system for point-of care use. We have assessed the performance characteristics of the SAMBA HIV-1 Semi-Q Test on SAMBA I and SAMBA II systems according to the Common Technical Specifications of the European Community's 98/79 In Vitro Diagnostic Medical Devices Directive. The sensitivity, specificity, reproducibility, and viral subtype coverage of the test were similar on the SAMBA I and SAMBA II platforms. The clinical performance on the SAMBA I system was compared with the Roche CAP/CTM assay and evaluated in-house with 130 patient specimens from London as well as in the field with 390 specimens in Kenya and Zimbabwe. The overall concordance between the SAMBA and CAP/CTM assays was 98.1%. The clinical performance of the test on the SAMBA II platform in comparison with the Abbott HIV-1 RealTime Assay was evaluated in-house with 150 specimens from Ukraine, yielding a concordance of 98.0%. The results thus show that the SAMBA HIV-1 Semi-Q Test performs equivalently on SAMBA I and SAMBA II, and they suggest that the test is suitable for implementation at the point-of-care in resource-poor regions where viral load testing is desperately needed but often unavailable.

Patient Experiences of Decentralized HIV Treatment and Care in Plateau State, North Central Nigeria: A Qualitative Study

Background. Decentralization of care and treatment for HIV infection in Africa makes services available in local health facilities. Decentralization has been associated with improved retention and comparable or superior treatment outcomes, but patient experiences are not well understood. Methods. We conducted a qualitative study of patient experiences in decentralized HIV care in Plateau State, north central Nigeria. Five decentralized care sites in the Plateau State Decentralization Initiative were purposefully selected. Ninety-three patients and 16 providers at these sites participated in individual interviews and focus groups. Data collection activities were audio-recorded and transcribed. Transcripts were inductively content analyzed to derive descriptive categories representing patient experiences of decentralized care. Results. Patient participants in this study experienced the transition to decentralized care as a series of “trade-offs.” Advantages cited included saving time and money on travel to clinic visits, avoiding dangers on the road, and the “family-like atmosphere” found in some decentralized clinics. Disadvantages were loss of access to ancillary services, reduced opportunities for interaction with providers, and increased risk of disclosure. Participants preferred decentralized services overall. Conclusion. Difficulty and cost of travel remain a fundamental barrier to accessing HIV care outside urban centers, suggesting increased availability of community-based services will be enthusiastically received.

Performance evaluation of the point-of-care SAMBA I and II HIV-1 Qual whole blood tests

The SAMBA HIV-1 Qual Whole Blood Test is a nucleic acid-based amplification assay for the qualitative detection of HIV-1 in whole blood of adults or infants. The test can be run on either the semi-automated SAMBA I system for clinical use or the fully automated, including readout, SAMBA II system for point-of-care use in resource-limited settings. We have assessed the performance characteristics of the SAMBA HIV-1 Qual Whole Blood Test on SAMBA I and SAMBA II. The limit of detection obtained for the two tests were 518IU/ml and 399copies/ml on SAMBA I and 457IU/ml and 433copies/ml on SAMBA II. Test specificity on both systems was 100% with a panel of 503 HIV-1 negative samples. Evaluation of test reproducibility showed 100% concordance with expected gold standard results as well as 100% agreement between operators, days, and runs as well as within runs on both SAMBA I and SAMBA II. Our results thus show that the SAMBA HIV-1 Qual Whole Blood Test performs equivalently on SAMBA I and SAMBA II, and also suggest that the test is suitable for implementation in medium-throughput clinical facilities (SAMBA I) or low-throughput point-of-care (POC) settings (SAMBA II) in resource-poor regions.