A simple method to elute cell-free HIV from dried blood spots improves their usefulness for monitoring therapy

The plasma separation card as a novel solution for enhancing central laboratory capability for HIV-1 viral load monitoring in limited-access settings

Measurement of HIV-1 viral load (VL) is essential for monitoring antiretroviral treatment (ART) efficacy. The preferred specimen type for VL is plasma, but in remote settings where collection and preservation of plasma many not be possible, dried blood spots (DBS) are often used instead. A new specimen collection matrix, the cobas plasma separation card (PSC, Roche Diagnostics Solutions), enables specimen preparation from a finger prick or venous blood, using a multi-layer absorption and filtration design that results in a specimen similar to dried plasma. We sought to confirm the correlation between VL results obtained using PSC prepared from venous blood to those from plasma or DBS, as well as PSC prepared with capillary blood from a finger prick. PSC, DBS and plasma were prepared with blood from HIV-1 infected persons attending a primary care clinic in Kampala, Uganda. VL in PSC and plasma was measured using cobas HIV-1 (Roche Diagnostics), while VL in DBS was measured with RealTime HIV-1 (Abbott Diagnostics). The correlation between VL from plasma and PSC made from capillary or venous blood was high (regression coefficient of determination r2 between 0.87 and 0.91), and there was good agreement based on mean bias (-0.14 to 0.24 log10 copies/mL) and classification of VL above or below 1000 copies/mL (91.4% agreement). In contrast, VL from DBS was lower than plasma or PSC (mean bias 0.51 to 0.63 log10 copies/mL) and not as well correlated (r2 0.78 to 0.81, 75.1-80.5% agreement). These results confirm the utility of PSC as an alternative specimen type for HIV-1 viral load measurement in areas where preparation and optimal storage or shipment of plasma is an obstacle to provision of treatment and care of HIV-1 infected people.

Use of whole blood and dried blood spot for detection of HIV-1 nucleic acids using reverse transcription loop-mediated isothermal amplification

For monitoring viral load (VL) or Early Infant Diagnosis (EID) of HIV-1, real-time Polymerase Chain Reaction (qPCR) is used to perform on plasma or Dried Blood Spot (DBS) sample. The qPCR method is expensive and requires sophisticated equipment. Therefore, there is a requirement for newer and cheaper technology for VL measurement or EID. In this analytical study, a Reverse Transcription-Loop-Mediated Isothermal Amplification (RT-LAMP) assay was optimized and applied for amplification of HIV nucleic acids (NA) extracted from plasma, heat-treated plasma, heat-treated whole blood and lysis buffer-treated dried blood spot (DBS). The amplified product of RT-LAMP assay was detected by color change of Hydroxy naphthol blue (HNB) dye, step ladder pattern band on agarose gel after electrophoresis and sigmoid-shaped curve in the real-time thermal cycler. Comparing the results from RT-LAMP testing of all conditions with the results obtained by RT-qPCR results, viewed as the gold standard; a relative analytical sensitivity and specificity of RT-LAMP was calculated as 100 % and 90 % respectively. The corresponding positive predictive value (PPV) and negative predictive value (NPV) were 93.75 % and 100 %, respectively. The percentage of agreement between the RT-LAMP and RT-qPCR was 88.46% and Cohen's kappa value was 0.75 shows a substantial agreement between the two tests. This study suggests that whole blood or DBS may be useful specimens for analysis by HIV-1 specific RT-LAMP, to provide a cost effective alternative to RT-qPCR for the detection of HIV-1 nucleic acid at the point of care, or in early infant diagnoses.

Performances of Dried Blood Spots and Point-of-Care Devices to Identify Virological Failure in HIV-Infected Patients: A Systematic Review and Meta-Analysis

To broaden access to HIV viral load monitoring (VLM), the use of blood samples from dried blood spots (DBS) or point-of-care (POC) devices, could be of great help in settings where plasma is not easily accessible. The variety of assays available makes the choice complex. This systematic review and meta-analysis aims to estimate the sensitivity and specificity of DBS and POC devices to identify patients in virological failure using World Health Organization (WHO) recommendations (viral load ≥1000 copies/mL), compared with plasma, for the assays currently available. Four databases were searched for articles, and two reviewers independently identified articles reporting sensitivity and specificity of DBS and/or POC to identify patients in virological failure. We excluded articles that used other thresholds as well as articles with a total number of participants below 50 to avoid reporting bias. Heterogeneity and factors associated with assays' performances were assessed by I² statistics and metaregression. The protocol of this review follows the PRISMA guidelines. Out of 941 articles, 47 were included: 32 DBS evaluations and 16 POC evaluations. Overall, when using DBS, the Abbott RT HIV-1, Roche CAP-CTM, NucliSENS BioMerieux and Aptima assays presented sensitivity and specificity exceeding 85%, but reported results were highly heterogeneous. Factors associated with better performances were high volume of blood and the use of the same assay for DBS and plasma VLM. Regarding the POC devices, SAMBA I, SAMBA II, and GeneXpert devices presented high sensitivity and specificity exceeding 90%, with less heterogeneity. DBS is suitable VLM, but performances can vary greatly depending on the protocols, and should be performed in trained centers. POC is suitable for VLM with less risk of heterogeneity but is more intensive in costs and logistics.

The performance of using dried blood spot specimens for HIV-1 viral load testing: A systematic review and meta-analysis

BACKGROUND

Accurate routine HIV viral load testing is essential for assessing the efficacy of antiretroviral treatment (ART) regimens and the emergence of drug resistance. While the use of plasma specimens is the standard for viral load testing, its use is restricted by the limited ambient temperature stability of viral load biomarkers in whole blood and plasma during storage and transportation and the limited cold chain available between many health care facilities in resource-limited settings. Alternative specimen types and technologies, such as dried blood spots, may address these issues and increase access to viral load testing; however, their technical performance is unclear. To address this, we conducted a meta-analysis comparing viral load results from paired dried blood spot and plasma specimens analyzed with commonly used viral load testing technologies.

METHODS AND FINDINGS

Standard databases, conferences, and gray literature were searched in 2013 and 2018. Nearly all studies identified (60) were conducted between 2007 and 2018. Data from 40 of the 60 studies were included in the meta-analysis, which accounted for a total of 10,871 paired dried blood spot:plasma data points. We used random effects models to determine the bias, accuracy, precision, and misclassification for each viral load technology and to account for between-study variation. Dried blood spot specimens produced consistently higher mean viral loads across all technologies when compared to plasma specimens. However, when used to identify treatment failure, each technology compared best to plasma at a threshold of 1,000 copies/ml, the present World Health Organization recommended treatment failure threshold. Some heterogeneity existed between technologies; however, 5 technologies had a sensitivity greater than 95%. Furthermore, 5 technologies had a specificity greater than 85% yet 2 technologies had a specificity less than 60% using a treatment failure threshold of 1,000 copies/ml. The study's main limitation was the direct applicability of findings as nearly all studies to date used dried blood spot samples prepared in laboratories using precision pipetting that resulted in consistent input volumes.

CONCLUSIONS

This analysis provides evidence to support the implementation and scale-up of dried blood spot specimens for viral load testing using the same 1,000 copies/ml treatment failure threshold as used with plasma specimens. This may support improved access to viral load testing in resource-limited settings lacking the required infrastructure and cold chain storage for testing with plasma specimens.

HIV viral load assays when used with whole blood perform well as a diagnostic assay for infants

Objective

Over the past several years, only approximately 50% of HIV-exposed infants received an early infant diagnosis test within the first two months of life. While high attrition and mortality account for some of the shortcomings in identifying HIV-infected infants early and putting them on life-saving treatment, fragmented and challenging laboratory systems are an added barrier. We sought to determine the accuracy of using HIV viral load assays for infant diagnosis of HIV.

Methods

We enrolled 866 Ugandan infants between March–April 2018 for this study after initial laboratory diagnosis. The median age was seven months, while 33% of infants were less than three months of age. Study testing was done using either the Roche or Abbott molecular technologies at the Central Public Health Laboratory. Dried blood spot samples were prepared according to manufacturer-recommended protocols for both the qualitative and quantitative assays. Viral load test samples for the Roche assay were processed using two different buffers: phosphate-buffered saline (PBS: free virus elution viral load protocol [FVE]) and Sample Pre-Extraction Reagent (SPEX: qualitative buffer). Dried blood spot samples were processed for both assays on the Abbott using the manufacturer’s standard infant diagnosis protocol. All infants received a qualitative test for clinical management and additional paired quantitative tests.

Results

858 infants were included in the analysis, of which 50% were female. Over 75% of mothers received antiretroviral therapy, while approximately 65% of infants received infant prophylaxis. The Roche SPEX and Abbott technologies had high sensitivity (>95%) and specificity (>98%). The Roche FVE had lower sensitivity (85%) and viral load values.

Conclusions

To simplify and streamline laboratory practices, HIV viral load may be used to diagnose HIV infection in infants, particularly using the Roche SPEX and Abbott technologies.

Classification of HIV-1 virological treatment failure using the Roche cobas plasma separation card on cobas 8800 compared to dried blood spots on Abbott RealTime HIV-1

BACKGROUND

Measurement of HIV-1 viral load (VL) is essential for monitoring antiretroviral treatment (ART) efficacy. In remote settings, dried blood spots (DBS) may be used as the specimen type. However, cellular components in DBS not present in the gold standard specimen type, plasma, may result in low specificity i.e., over-estimation of VL results from DBS compared to plasma. The Abbott RealTime HIV-1 assay system has been reported to have improved specificity using DBS compared to other tests. A new specimen collection matrix, the cobas plasma separation card (PSC, Roche Molecular Systems), enables specimen collection from a finger prick or venous blood, using a multi-layer absorption and filtration design that results in a specimen similar to plasma.

OBJECTIVES AND STUDY DESIGN

We performed a direct comparison between VL results from PSC tested with the cobas 6800/8800 assay (c8800) and DBS tested with the Abbott RealTime HIV-1 assay.

RESULTS

Overall concordance between PSC and plasma around the 1000 copies/mL threshold was high (>97%). Compared to VL measured using DBS and the RealTime assay, PSC and c8800 showed improved sensitivity (96.9% vs 90.6%) and specificity (97.4% vs. 87.2%) using plasma as the reference, as there were fewer patients with VL below 1000 copies/mL in plasma in whom VL was over this threshold using PSC compared to DBS. The limit of detection for PSC was lower than for DBS (575 vs. 2314 copies/mL).

CONCLUSIONS

cobas PSC represents a promising specimen type for use with the cobas 6600/8800 system in settings where plasma cannot be used.

Comparison of Alere q whole blood viral load with DBS and plasma viral load in the classification of HIV virological failure

Background

In remote settings, timely plasma separation and transportation to testing laboratories is an impediment to the access of HIV viral load (VL) testing. Potential solutions are whole blood testing through point of care (POC) assays or dried blood spots (DBS).

Methods

We evaluated the performance of a prototype Alere q whole blood VL protocol and compared it against plasma (Abbott RealTime HIV-1) and DBS VL (Abbott RealTime HIV-1 DBS revised prototype protocol and Roche CAP/CTM HIV-1 v2.0 DBS free virus elution protocol). Virological failure (VF) was defined at >1000 copies/ml.

Results

Of 299 samples, Alere q correctly classified VF in 61% versus 87% by Abbott DBS and 76% by Roche FVE. Performance varied across plasma VL categories. Alere q showed 100% sensitivity. Below 1000 copies/ml of plasma, Alere q demonstrated over-quantification, with 19% specificity. Abbott DBS had 91% sensitivity and the best overall correlation with plasma (r² = 0.72). Roche FVE had the best specificity of 99% but reduced sensitivity of 52%, especially between 1000–10,000 copies/ml of plasma. Correlation was best for all assays at >10,000 copies/ml.

Conclusion

Variability was prominent between the assays. Each method requires optimization to facilitate the implementation of a cut-off with optimal sensitivity and specificity for VF. Although Alere q whole blood assay exhibited excellent sensitivity, the poor specificity of only 19% would lead to unnecessary switching of regimens. Thus any VF detected would need to be confirmed by a more specific assay. Both the Abbott DBS and Roche FVE protocols showed good specificity, however sensitivity was reduced when the plasma VL was 1000–10,000 copies/ml. This could result in delays in detecting VF and accumulation of drug resistance. Field evaluation in settings that have adopted these DBS protocols are necessary.

Separation of Plasma from Whole Blood by Use of the cobas Plasma Separation Card: a Compelling Alternative to Dried Blood Spots for Quantification of HIV-1 Viral Load

Plasma HIV viral load testing is the preferred means of monitoring antiretroviral treatment response. Dried blood spots (DBSs) hold considerable logistical advantages over EDTA samples, but they more frequently misclassify virological failure and have higher limits of detection (LoD). Plasma separation cards (PSCs) may overcome these limitations. Health workers collected EDTA whole blood by venipuncture and 140 μl of finger-prick blood by capillary tube from 53 HIV-infected adults. Capillary blood was immediately transferred to PSCs. Additionally, 432 EDTA samples from HIV-infected adults were spotted onto PSCs and analyzed together with the finger-prick samples. Specificity and sensitivity of PSC with paired EDTA-PSC samples tested on a cobas 6800/8800 system with the cobas HIV-1 test (cobas HIV) was determined. LoD (3rd HIV-1 WHO International Standard) and stability at a range of temperatures and storage durations was determined using cobas HIV and cobas AmpliPrep/cobas TaqMan HIV-1 test v2.0 (CAP/CTM). Of 132 specimens with quantitative values for paired EDTA-PSC samples, the mean log₁₀ difference between samples was 0.05 copies/ml (95% confidence interval [CI], -0.01 to 0.11). The LoD for cobas HIV was 790.2 copies/ml and for CAP/CTM was 737.9 copies/ml. At 1,000 copies/ml, PSC sensitivity was 97.0% (128/132) and specificity was 97.2% (343/353). Results correlated well with those from EDTA samples (Deming R ² = 0.90). PSC results were unaffected by temperature and storage conditions. PSC samples correlate well with plasma viral load and have adequate sensitivity and specificity. The improved performance may be as a result of a reduction in contribution from cell-associated viral nucleic acids. The card provides an alternative sample collection technology to DBSs.

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 dried blood spot as an alternative sample collection method for hepatitis C virus RNA quantitation and genotyping using a commercial system

Dried blood spot (DBS) is a minimally invasive sampling method suitable for sample collection, storage and transportation in resource limited areas. Aim of this study was to compare the diagnostic utility of DBS with plasma sample for HCV RNA quantitation and genotyping using commercial systems. Plasma and DBS card spotted samples were collected from 95 HCV seropositive patients. Both types of samples were subjected to HCV RNA by real-time PCR (Abbott m2000rt, USA). Genotyping was performed using Abbott HCV genotype II kit (Abbott diagnostics, USA) in samples with viral load > 3 log10 IU/ml. In both plasma and DBS, 14 (14.7%) samples were negative and 81 (85.3%) were positive for HCV RNA. Median viral load in plasma (3.78; range 0-7.43) log10 IU/ml was comparable to DBS (3.93; range 0-7.24) log10 IU/ml. DBS demonstrated sensitivity and specificity of 97.5 and 85.7% respectively, with positive predictive value (PPV) of 97.5% and negative predictive value (NPV) of 85.7%. DBS showed good correlation (r2 = 0.866) and agreement (93.5%) with plasma. Genotyping in 20 patients showed 100% concordance between DBS and plasma samples. DBS showed good sensitivity and specificity as a sampling method for HCV RNA quantitation and genotyping.

Sensitivity and specificity of two dried blood spot methods for HIV-1 viral load monitoring among patients in Hanoi, Vietnam

The use of dried blood spot (DBS) specimens for HIV viral load (VL) monitoring is recommended to support the roll-out of routine VL monitoring in low and middle income countries (LMICs). To better understand the use of DBS for VL monitoring, we evaluated two DBS testing methods, Roche TaqMan® Free Virus Evolution protocol (DBS-FVE) and Roche TaqMan® SPEX protocol (DBS-SPEX)) in patients receiving ART at an HIV clinic in Hanoi, Vietnam. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for each DBS testing method at the thresholds of 1000 and 5000 copies/ml compared to plasma VL. At a threshold of 1000 copies/ml, sensitivity, specificity, PPV and NPV of the DBS-SPEX method were 98.8% (95% CI: 93.3%-100%), 74.3% (95% CI: 70.8%-77.5%), 31.5% (95% CI: 25.8%-37.6%), and 99.8% (95% CI: 98.9%-100%), respectively. Increasing the VL threshold value to 5000 copies/ml improved specificity (97.9% CI: 96.6%-98.9%) and PPV (83.9% CI: 74.5%-90.9%). Using the DBS-FVE method, at the threshold of 1000 copies/ml and with a correction factor of +0.3 log copies/ml, sensitivity was 95.1% (87.8%-98.6%) and specificity was 98.8% (97.7%-99.5%). Sensitivity decreased at the threshold of 5000 copies/ml (65.8%, 95% CI: 54.3%-76.1%). With a correction factor of +0.7 log copies/ml, the sensitivity was 96.3% (89.6%-99.2%) and specificity was 98.2% (96.9%-99.1%) at the threshold of 1000 copies/ml. We found that the Roche DBS-FVE method, with a +0.7 log copies/ml correction factor, performed well with sensitivity and specificity greater than 96% at a VL threshold of 1000 copies/m. These findings add to the growing body of evidence supporting the use of DBS VL testing for ART monitoring. Future research should evaluate the association between VL results by DBS and clinical outcome measures such as HIV drug resistance, morbidity, and mortality.

Comparison of different nucleic acid preparation methods to improve specific HIV-1 RNA isolation for viral load testing on dried blood spots

In resource-limited countries (RLCs), WHO recommends HIV viral load (VL) on dried blood spots (DBS) for antiretroviral therapy (ART) monitoring of patients living in non-urban settings where plasma VL is not available. In order to reduce the impact of proviral DNA interference, leading to false positive results in samples with low plasma VL, we compared three different nucleic acid preparation methods with the NucliSens (Biomérieux) extraction, known for its high recovery of nucleic acids on DBS. Paired plasma-DBS samples (n=151) with predominantly low plasma VL (≤10,000 copies/ml; 74%) were used. At the threshold of 1,000 copies/ml on DBS, 51% and 10% were misclassified as false positives or false negatives, respectively with NucliSens, versus 41% and 20% with m2000sp (Abbott), described as more specific for RNA recovery. DNase treatments of nucleic acid extracts and free virus elution (FVE) protocol before nucleic acid extraction, reduced the proportion of false positives to 0% and 19%, but increased the proportion of false negatives to 40% and 73%. More efforts are thus still needed to improve performance of VL assays on DBS to monitor patients on ART in RLCs and allow timely switch to more costly second or third line ART regimes.

A Simple Phosphate-Buffered-Saline-Based Extraction Method Improves Specificity of HIV Viral Load Monitoring Using Dried Blood Spots

Although Roche COBAS Ampliprep/COBAS TaqMan (CAP/CTM) systems are widely used in sub-Saharan Africa for early infant diagnosis of HIV from dried blood spots (DBS), viral load monitoring with this system is not practical due to nonspecific extraction of both cell-free and cell-associated viral nucleic acids. A simplified DBS extraction technique for cell-free virus elution using phosphate-buffered saline (PBS) may provide an alternative analyte for lower-cost quantitative HIV virus load (VL) testing to monitor antiretroviral therapy (ART). We evaluated the CAP/CTM v2.0 assay in 272 paired plasma and DBS specimens using the cell-free virus elution method and determined the level of agreement, sensitivity, and specificity at thresholds of target not detected (TND), target below the limit of quantification (BLQ) (<20 copies/ml in plasma or <400 copies/ml in DBS), and VL of <1,000 copies/ml, and VL of <5,000 copies/ml. Reported plasma VL ranged from TND, or <20, to 5,781,592 copies/ml, and DBS VL ranged from TND, or <400, to 467,600 copies/ml. At <1000 copies/ml, agreement between DBS and plasma was 96.7% (kappa coefficient, 0.93; P < 0.0001). The mean difference between DBS and plasma VL values was -1.06 log10 copies/ml (95% confidence interval [CI], -1.17, -0.97; P < 0.0001). At a treatment failure threshold of >1,000 copies/ml, the sensitivities, specificities, positive predictive values (PPV), and negative predictive values (NPV) were 92.7%, 100%, 100%, and 94.3%, respectively. PBS elution of DBS offers a sensitive and specific method for monitoring plasma viremia among adults and children on ART at the WHO-recommended threshold of >1,000 copies/ml on the Roche CAP/CTM system.

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.

Evaluation of Two Techniques for Viral Load Monitoring Using Dried Blood Spot in Routine Practice in Vietnam (French National Agency for AIDS and Hepatitis Research 12338)

Background. Although it is the best method to detect early therapeutic failure, viral load (VL) monitoring is still not widely available in many resource-limited settings because of difficulties in specimen transfer, personnel shortage, and insufficient laboratory infrastructures. Dried blood spot (DBS) use, which was introduced in the latest World Health Organization recommendations, can overcome these difficulties. This evaluation aimed at validating VL measurement in DBS, in a laboratory without previous DBS experience and in routine testing conditions.

Methods. Human immunodeficiency virus (HIV)-infected adults were observed in a HIV care site in Hanoi, and each patient provided 2 DBS cards with whole blood spots and 2 plasma samples. Viral load was measured in DBS and in plasma using the COBAS Ampliprep/TaqMan and the Abbott RealTime assays. To correctly identify those with VL ≥ 1000 copies/mL, sensitivity and specificity were estimated.

Results. A total of 198 patients were enrolled. With the Roche technique, 51 plasma VL were ≥1000 copies/mL; among these, 28 presented a VL in DBS that was also ≥1000 copies/mL (sensitivity, 54.9; 95% confidence interval [CI], 40.3–68.9). On the other hand, all plasma VL < 1000 copies/mL were also <1000 copies/mL in DBS (specificity, 100; 95% CI, 97.5–100). With the Abbott technique, 45 plasma VL were ≥1000 copies/mL; among these, 42 VL in DBS were also ≥1000 copies/mL (sensitivity, 93.3%; 95% CI, 81.7–98.6); specificity was 94.8 (95% CI, 90.0–97.7).

Conclusions. The Abbott RealTime polymerase chain reaction assay provided adequate VL results in DBS, thus allowing DBS use for VL monitoring.