Use of dried spots of whole blood, plasma, and mother's milk collected on filter paper for measurement of human immunodeficiency virus type 1 burden

Quantifying neutralising antibody responses against SARS-CoV-2 in dried blood spots (DBS) and paired sera

The ongoing SARS-CoV-2 pandemic was initially managed by non-pharmaceutical interventions such as diagnostic testing, isolation of positive cases, physical distancing and lockdowns. The advent of vaccines has provided crucial protection against SARS-CoV-2. Neutralising antibody (nAb) responses are a key correlate of protection, and therefore measuring nAb responses is essential for monitoring vaccine efficacy. Fingerstick dried blood spots (DBS) are ideal for use in large-scale sero-surveillance because they are inexpensive, offer the option of self-collection and can be transported and stored at ambient temperatures. Such advantages also make DBS appealing to use in resource-limited settings and in potential future pandemics. In this study, nAb responses in sera, venous blood and fingerstick blood stored on filter paper were measured. Samples were collected from SARS-CoV-2 acutely infected individuals, SARS-CoV-2 convalescent individuals and SARS-CoV-2 vaccinated individuals. Good agreement was observed between the nAb responses measured in eluted DBS and paired sera. Stability of nAb responses was also observed in sera stored on filter paper at room temperature for 28 days. Overall, this study provides support for the use of filter paper as a viable sample collection method to study nAb responses.

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.

Diagnostic Accuracy of Dried Plasma Spot Specimens for HIV-1 Viral Load Testing: A Systematic Review and Meta-analysis

BACKGROUND

Dried plasma spot specimens may be a viable alternative to traditional liquid plasma in field settings, but the diagnostic accuracy is not well understood.

METHODS

Standard databases (PubMed and Medline), conferences, and gray literature were searched until January 2019. The quality of evidence was evaluated using the Standards for Reporting Studies of Diagnostic Accuracy and Quality Assessment of Diagnostic Accuracy Studies-2 criteria. We used univariate and bivariate random effects models to determine misclassification, sensitivity, and specificity across multiple thresholds, overall and for each viral load technology, and to account for between-study variation.

RESULTS

We identified 23 studies for inclusion in the systematic review that compared the diagnostic accuracy of dried plasma spots with that of plasma. Primary data from 16 of the 23 studies were shared and included in the meta-analysis, representing 18 countries, totaling 1847 paired dried plasma spot:plasma data points. The mean bias of dried plasma spot specimens compared with that of plasma was 0.28 log10 copies/mL, whereas the difference in median viral load was 2.25 log10 copies/mL. More dried plasma spot values were undetectable compared with plasma values (43.6% vs. 29.8%). Analyzing all technologies together, the sensitivity and specificity of dried plasma spot specimens were >92% across all treatment failure thresholds compared and total misclassification <5.4% across all treatment failure thresholds compared. Some technologies had lower sensitivity or specificity; however, the results were typically consistent across treatment failure thresholds.

DISCUSSION

Overall, dried plasma spot specimens performed relatively well compared with plasma with sensitivity and specificity values greater than 90% and misclassification rates less than 10% across all treatment failure thresholds reviewed.

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.

An evaluation of solid versus liquid transport media for high-risk HPV detection and cervical cancer screening on self-collected specimens

Background

The solid transport media is a small size card that allows fast, easy DNA extraction from a variety of biological samples. In 2016 we developed a solid media transport card; for that pilot study to control the self-collection we used a pseudo-self-collection technique. The current study expands this prior work using true self-collections and only the POI card, and aims to evaluate the solid media transport card to detect HR-HPV in self-samples compared to liquid transport media.

Methods

Ten thousand eight hundred eighty-five women between the ages of 30–59 with no screening for 3 years were enrolled. The self-collected sample was first applied to a new solid media transport card (Labeled as SC) then the brush placed in 6 ml ThinPrep liquid (Labeled as SL). Then a physician collected a direct endocervical specimen into ThinPrep liquid (Labeled as DL). Samples were tested with Cobas 4800 and the SeqHPV NGS assay for HR-HPV. Patients positive on any test were recalled for colposcopy and biopsy.

Results

Ten thousand three hundred thirty-nine participants had complete data. The mean age was 43.9 years. CIN 2+ rates were 1.4% (142/10339). The agreement in HPV detection between the two different self-sample collection media was also good (Cobas HPV kappa = 0.86; SeqHPV kappa = 0.98). Tested with Cobas, the sensitivity of Cobas-SL and Cobas-SC for CIN 2+ was95.07 and 94.37%; and for CIN3+ was 96.30, 96.30% respectively. The specificity of Cobas-SC, and Cobas-SL for CIN2+ was 88.74 and 87.35%; for CIN3 was 88.04and 86.65% respectively. Tested with SeqHPV, the sensitivity for CIN2+ of Seq-SC and Seq-SL was 95.77 and 96.48%; for CIN3+, both the SC and SL specimens had a sensitivity of 100%. The specificity for CIN2+ of Seq-SC and Seq-SL was 89.54 and 89.53%; for CIN3+ was 88.84,88.82% respectively. For both HR-HPV assays, the sensitivities were similar for the two self-sample media (SC vs SL, p = 1.00).

Conclusions

The solid transport card for collecting vaginal self-samples as accurate as liquid transport media assayed by two different PCR based HR-HPV tests. The solid transport media is a suitable medium for collecting and storing vaginal self-samples.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13027-020-00333-4.

Hepatitis C Virus (HCV) RNA screening and sequencing using dry plasma spots

BACKGROUND

HCV RNA screening of large sample repositories provides data on HCV epidemic patterns that may help guide control policies. In resource-limited settings, shipment of frozen samples to molecular laboratory facilities and testing of individual samples may be prohibitively expensive.

OBJECTIVE

Our aim was to detect and sequence HCV RNA in a large HIV-positive cohort from Kumasi, Ghana, using pooled and individual dried plasma spots (DPS) produced from samples stored at -80°C.

STUDY DESIGN

In the validation phase, replicate DPS were prepared with six dilutions (500-10,000 IU/ml) of the 4^th International Standard for HCV and tested in three independent experiments. In the testing phase, DPS prepared with plasma samples from 875 HIV-positive subjects were pooled for screening, followed by testing of individual DPS of positive pools. Input from individual DPS was two 6mm punches; pools comprised two punches from each of five DPS. Genotypes were determined by Sanger sequencing of HCV core and NS5B.

RESULTS

With the dilution series, sensitivity of HCV RNA detection was ≥2500 IU/ml. Replicate DPS gave intra-assay and inter-assay coefficients of variation ≤1.4%. With the stored samples, HCV RNA was detected in 5/175 DPS pools and in one DPS from each positive pool, yielding a HCV RNA prevalence of 5/875 (0.57%; 95% confidence interval 0.07-1.07%). The five samples were sequenced as HCV genotypes 2l and 2r.

DISCUSSION

DPS allowed reproducible HCV RNA detection, and pooling effectively contained the cost and labour of screening a previously untested, low-prevalence cohort. DPS were also suitable for HCV sequencing.

Evaluation of human papillomavirus detection by Abbott m2000 system on samples collected by FTA Elute™ Card in a Chinese HIV-1 positive population

BACKGROUND

HIV+/AIDS women have an increased risk of developing into CIN and cervical cancer compared to the general population. Limited medical resource and the lack of AIDS relevant knowledge impair the coverage and efficiency of cervical cancer screening.

OBJECTIVES

To compare the clinical performance of self-collected dry storage medium (FTA Elute card) and physician-collected PreservCyt medium in detection of high risk human papillomavirus (HR HPV) among HIV-1 positive population.

METHODS

Three hundred HIV-1 positive women (aged 25-65) were recruited from Yunnan infectious hospital. Two cervicovaginal samples were collected from each participant: one was collected by the women themselves and applied on a FTA Elute card; the other one was collected by a physician and stored in PreservCyt solution. All the samples were tested for 14 HR HPV using Abbott RealTime High Risk HPV assay. Biopsies were taken for histological diagnosis if any abnormal impression was noticed under colposcopy.

RESULTS

291 (97.0%) of participants were eligible for this study. 101 (34.70%) participants were found HR HPV positive in both FTA card and PreservCyt samples, and 19 (6.53%) women were diagnosed as CIN2+. The HR HPV positive rate on samples collected by FTA Elute card and PreservCyt solution was 42.61% and 39.86%, respectively. The overall agreement was 87% (kappa=0.731) between FTA card and PreservCyt. The clinical sensitivity and specificity of FTA card and PreservCyt were 100%, 61.39% and 100%, 64.33%, respectively.

CONCLUSIONS

In this study, FTA Elute card demonstrated a good performance on self-collected sample for HR HPV detection in HIV-1 positive population. For the women from low-resource area with HIV-1 infection, FTA Elute card could be an attractive sample collection method for cervical cancer screening.

Evaluation of a new solid media specimen transport card for high risk HPV detection and cervical cancer prevention

BACKGROUND

Solid media transport can be used to design adaptable cervical cancer screening programs but currently is limited by one card with published data.

OBJECTIVE

To develop and evaluate a solid media transport card for use in high-risk human papillomavirus detection (HR-HPV).

STUDY DESIGN

The Preventative Oncology International (POI) card was constructed using PK 226 paper(®) treated with cell-lysing solution and indicating dye. Vaginal samples were applied to the POI card and the indicating FTA (iFTA) elute card. A cervical sample was placed in liquid media. All specimens were tested for HR-HPV. Color change was assessed at sample application and at card processing. Stability of the POI card and iFTA elute card was tested at humidity.

RESULTS

319 women were enrolled. Twelve women had at least one insufficient sample with no difference between media (p=0.36). Compared to liquid samples, there was good agreement for HR-HPV detection with kappa of 0.81 (95% CI 0.74-0.88) and 0.71 (95% CI 0.62-0.79) for the POI and iFTA elute card respectively. Sensitivity for ≥CIN2 was 100% (CI 100-100%), 95.1% (CI 92.7-97.6%), and 93.5% (CI 90.7-96.3%) for the HR-HPV test from the liquid media, POI card, and iFTA elute card respectively. There was no color change of the POI card noted in humidity but the iFTA elute card changed color at 90% humidity.

CONCLUSIONS

The POI card is suitable for DNA transport and HR-HPV testing. This card has the potential to make cervical cancer screening programs more affordable worldwide.

Stability of HIV-1 Nucleic Acids in Dried Blood Spot Samples for HIV-1 Drug Resistance Genotyping

Dried blood spots (DBS) are an easy to collect sample-type that can stabilize biological material at ambient temperature for transport and storage, making them ideal for use in resource-limited settings (RLS). We investigated the effect of storage temperature and duration on ability to detect mixed HIV-1 viral RNA populations, and subsequently viral RNA populations in a background of proviral DNA. Part one of the study used DBS samples of whole blood spiked with specific quantities of HIV-1 subtype-B and -C RNA to study mixed virus population detection. Part two used DBS comprising of HIV-1 subtype-B proviral DNA containing U1 cells combined with HIV-1 subtype-C RNA to mimic HIV-1 infected clinical samples as a model system to study the relative stability of HIV-1 RNA and DNA in DBS. Prepared DBS were stored at -20 °C and +30 °C for periods of one day, one, two, and four weeks. Samples were genotyped to determine changes in the detection of mixtures in the sample over time. From two weeks onwards, storage at +30 °C resulted in gradual, time-related reduction in the detection of mixed virus population at log10 VL 4.0 but not at log10 5.0. Proviral DNA and viral RNA were both stable for at least 52 weeks when stored at -20 °C, compared to progressive RNA decay over time at +30 °C. DBS storage conditions and duration had a significant effect on HIV-1 RNA amplification. Our results demonstrate that DBS storage at ambient temperature (+30 °C) should not exceed two weeks, with long-term storage at -20 °C or lower.

Development and evaluation of a one step reverse transcription-loop mediated isothermal amplification assay (RT-LAMP) for rapid detection of foot and mouth disease virus in India

A simple, rapid and sensitive diagnostic assay for Foot-and-mouth disease (FMD) is required for deployment in the field. In this study, development of Reverse Transcription-Loop Mediated Isothermal Amplification (RT-LAMP) assay based on the 3D polymerase gene for specific and rapid detection FMD virus (FMDV) was carried out. The assay was optimised with viral RNA extracted from serotype O, A and Asia 1 FMDV vaccine strains, which resulted a reliable amplification at 65 °C for 60 min. The amplified RT-LAMP products were identified by agarose gel electrophoresis with ethidium bromide staining or observation by naked eye for the presence of turbidity and colour change following the addition of hydroxyl naphthol blue (HNB). The specificity of the assay was demonstrated by the absence of amplification of genome extracted from other viruses or cellular origin. With respect to analytical sensitivity the developed RT-LAMP assay was found more sensitive than routinely used multiplex PCR (mPCR). Further, the assay was evaluated with RNA extracted from cell cultured isolates (n = 50), tongue epithelial samples (n = 150) and semen samples from infected bulls (n = 13). In conclusion, RT-LAMP with HNB dye was shown to be simple, specific and sensitive assay for rapid diagnosis of FMDV infection. Further, the assay has the potential for field deployment and use for rapid FMDV surveillance in India.

An overview of the clinical use of filter paper in the diagnosis of tropical diseases

Tropical infectious diseases diagnosis and surveillance are often hampered by difficulties of sample collection and transportation. Filter paper potentially provides a useful medium to help overcome such problems. We reviewed the literature on the use of filter paper, focusing on the evaluation of nucleic acid and serological assays for diagnosis of infectious diseases using dried blood spots (DBS) compared with recognized gold standards. We reviewed 296 eligible studies and included 101 studies evaluating DBS and 192 studies on other aspects of filter paper use. We also discuss the use of filter paper with other body fluids and for tropical veterinary medicine. In general, DBS perform with sensitivities and specificities similar or only slightly inferior to gold standard sample types. However, important problems were revealed with the uncritical use of DBS, inappropriate statistical analysis, and lack of standardized methodology. DBS have great potential to empower healthcare workers by making laboratory-based diagnostic tests more readily accessible, but additional and more rigorous research is needed.

An evaluation of different saliva collection methods for detection of antibodies against hepatitis C virus (anti-HCV)

BACKGROUND

Saliva samples can be used as an alternative fluid for against hepatitis C virus (anti-HCV) detection owing to the ease of collection and excellent acceptability. This study was conducted to optimize a commercial enzyme immunoassay (EIA) to detect anti-HCV in saliva samples.

METHODS

Ninety-six individuals donated paired serum and saliva samples that were obtained, using a commercial device (Salivette) and spitting into a sterile container. Initially, elution buffer for the Salivette samples, sample volume, incubation time and temperature, and two different anti-HCV EIAs were evaluated. Using the optimized assay, three methods for cut-off calculation were also evaluated.

RESULTS

A 20-fold increase in the sample volume for both collection methods was needed. Moreover, the Radim assay was the most appropriate assay for anti-HCV detection in saliva samples, and the quality parameters were increased when a ROC curve was used to determine the cut-off value. Using this optimized assay, the sensitivities, specificities, accuracies, positive and negative predictive values were above 90% for saliva obtained using both the Salivette and spitting methods. Using this assay, discordant false-negative results were obtained for only two Salivette samples and five spitting samples. The concordance kappa was 93% for the Salivette method and 86.1% for the spitting method, demonstrating excellent performance.

CONCLUSIONS

Saliva samples obtained for both methods can be employed for anti-HCV detection among HCV-infected or HCV-suspected cases, but several modifications must be performed on commercial EIAs to obtain good results. Moreover, samples obtained with commercial devices are more appropriate for anti-HCV detection in saliva samples.

[Dried blood spots for monitoring HIV infection in Public Health Programs in developing countries]

As access to antiretroviral treatment increases in the developing countries, efforts towards making it easier and less costly to collect, store, and deliver the biological samples to reference laboratories, where the serological and genetic diagnosis techniques are performed, have become a high priority. Blood sampling on filter papers is an inexpensive and practical alternative to plasma for antiretroviral treatment monitoring in countries with limited resources and no access to cold chains or refrigeration. The main clinical applications and uses of blood-sampling onto filter papers (dried blood spots [DBS]) are reviewed, focusing on how these can be applied in monitoring HIV infection, particularly for use in National Health Programs in developing countries, or in resource-limited settings. A review is presented of studies that have used the DBS technique for quantifying viral load, analysis of antiretroviral drug-resistance mutations, early infant diagnosis, adult serological diagnosis, detection of viral p24 antigen, and molecular epidemiology of HIV-1, in different geographical locations. Those variables that could affect the use of DBS, particularly in the HIV field, as well as explaining how these procedures can be optimised to increase their sensitivity are also reviewed. The aim of this study was to review the advantages of implementing the DBS technique in the HIV field, especially in resource-constrained regions.

Dried blood spots versus plasma for the quantitation of HIV-1 RNA using a real-Time PCR, m2000rt assay

High costs and stringent requirements for storage and transport of plasma, often prohibit the availability of HIV viral load quantification in resource-limited settings. Dried blood spots (DBS) represent a better method of specimen collection that removes many of these logistical and technical limitations. The present study aimed to assess the performance of the Abbott m2000rt assay for quantitation of HIV-1 RNA in DBS specimens using plasma as a "gold standard" for comparison. One hundred paired DBS and plasma specimens were collected from patients infected with HIV, who were 18 years and older during routine visits to a private tertiary-care clinic in Chennai, India. HIV-1 RNA was extracted manually and then detected using the m2000rt assay. The mean plasma and DBS viral loads were 4.27 (95% CI: 2.65, 5.88) and 4.14 (95% CI: 1.96, 6.32) log copies/mL, respectively. The overall sensitivity of DBS reached 95%; with sensitivities of 62%, 88% and 100% when stratified by viral load ranges of ≤1000, 1000-3000 and >3000 copies/mL, respectively. An over quantitation of the viral load with DBS was observed in pairs with plasma viral load<3000 copies/mL [d=-0.3 log copies/mL (ranging from -0.1 to 0.6 log copies/mL)]. The study showed a strong concordance in RNA levels between plasma and DBS. The use of DBS specimens should be considered for HIV monitoring and for detection of virologic failure in resource-limited settings.

Development and evaluation of an assay for HIV-1 protease and reverse transcriptase drug resistance genotyping of all major group-M subtypes

BACKGROUND

High cost and varying sensitivity for non-B HIV-1 subtypes limits application of current commercial kits for HIV-1 drug resistance genotyping of all major HIV-1 group-M subtypes.

OBJECTIVES

Our research aimed to develop and validate an assay specific for all major HIV-1 group-M subtypes for use as an alternative to commercial assays for HIV-1 protease (PR) and reverse transcriptase (RT) drug resistance genotyping.

STUDY DESIGN

A nested RT-PCR encompassing the entire PR and RT up to amino acid 321 of HIV-1 was designed to detect HIV-1 group-M subtypes. Primers compatible with group-M subtypes were defined and analytical sensitivity of the assay evaluated using a panel of reference viruses for subtypes A-H and CRF01_AE. The assay was subsequently evaluated on 246 plasma samples from HIV-1 infected individuals harboring various group-M subtypes and viral loads (VLs).

RESULTS

All major group-M HIV-1 subtypes were detected with an overall analytical sensitivity of 1.00E+03 RNA copies/ml. Application of the genotyping assay on 246 primarily African clinical samples comprising subtypes A (n=52; 21.7%), B (n=12; 5.0%), C (n=127; 52.9%), D (n=25; 10.4%), CRF01_AE (n=10; 4.2%), and CRF02_AG (n=10; 4.2%), and unassigned variants (n=10; 4.2%), VL range 4.32E+02-8.63E+06 (median 2.66E+04) RNA copies/ml, was ∼98% successful.

CONCLUSIONS

A group-M subtype-independent genotyping assay for detection of HIV-1 drug resistance was developed. The described assay can serve as an alternative to commercial assays for HIV-1 drug resistance genotyping in routine diagnostics, and for surveillance and monitoring of drug resistance in resource-limited settings (RLS).

Implementation of HIV early infant diagnosis and HIV type 1 RNA viral load determination on dried blood spots in Cameroon: challenges and propositions

The testing of dried blood spots (DBSs) for human immunodeficiency type 1 (HIV-1) proviral DNA by PCR is a technology that has proven to be particularly valuable in diagnosing exposed infants. We implemented this technology for HIV-1 early infant diagnosis (EID) and HIV-1 RNA viral load determination in infants born of HIV-1-seropositive mothers from remote areas in Cameroon. The samples were collected between December 2007 and September 2010. Fourteen thousand seven hundred and sixty-three (14,763) DBS samples from infants born of HIV-positive mothers in 108 sites nationwide were tested for HIV. Of these, 1452 were positive on first PCR analyses (PCR1), giving an overall infection rate of 12.30%. We received only 475 DBS specimen for a second PCR testing (PCR2); out of these, 145 were positive. The median HIV-1 RNA viral load for 169 infant DBS samples tested was 6.85 log copies/ml, with values ranging from 3.37 to 8 log copies/ml. The determination of the viral load on the same DBS as that used for PCR1 allowed us to bypass the PCR2. The viral load values were high and tend to decrease with age but with a weak slope. The high values of viral load among these infants call for early and effective administration of antiretroviral therapy (ART). The findings from this study indicate that the use of DBS provides a powerful tool for perinatal screening programs, improvement on the testing algorithm, and follow-up during treatment, and thus should be scaled up to the entire nation.

Low-cost assays for monitoring HIV infected individuals in resource-limited settings

Use of a combination of CD4 counts and HIV viral load testing in the management of antiretroviral therapy (ART) provides higher prognostic estimation of the risk of disease progression than does the use of either test alone. The standard methods to monitor HIV infection are flow cytometry based for CD4+ T cell count and molecular assays to quantify plasma viral load of HIV. Commercial assays have been routinely used in developed countries to monitor ART. However, these assays require expensive equipment and reagents, well trained operators, and established laboratory infrastructure. These requirements restrict their use in resource-limited settings where people are most afflicted with the HIV-1 epidemic. With the advent of low-cost and/or low-tech alternatives, the possibility of implementing CD4 count and viral load testing in the management of ART in resource-limited settings is increasing. However, an appropriate validation should have been done before putting them to use for patient testing.

Dried blood spots in HIV monitoring: applications in resource-limited settings

By the end of 2008, 4 million people were receiving antiretroviral treatment for HIV/AIDS in low- and middle-income countries. In industrialized countries, monitoring of treatment with viral load measurements and drug resistance testing is the standard of care to ensure early detection of treatment failure and a prompt switch to a fully active second-line regimen, before drug-resistant mutations accumulate. These tests, however, require highly specialized laboratories and stringent procedures for storage and shipment of plasma, and are rarely available in resource-limited settings. Therefore, treatment failure in such settings is usually not detected until patients develop severe immunodeficiency, at which stage widespread resistance is likely. Dried blood spots (DBS) are easy to collect and store, and can be a convenient alternative to plasma in settings with limited laboratory capacity. This review provides an overview of possible applications of DBS technologies in the monitoring of HIV treatment, with the main focus on viral load quantification and drug resistance testing.

HIV load testing with small samples of whole blood

Access to human immunodeficiency virus (HIV) viral load (VL) testing is of paramount importance for the success of antiretroviral therapy treatment campaigns throughout the world. In many countries, limited laboratory infrastructure and transport capacities preclude a substantial number of people infected with HIV from accessing the necessary testing. Point-of-care diagnostic testing methods for those with HIV infection provide a compelling solution to addressing this challenge. To facilitate ease of use in such tests, finger-stick whole blood (WB) would constitute an ideal sample type if test performance equivalent to laboratory testing could be ensured. To determine the diagnostic sensitivity of a VL assay based on small volumes of WB, we analyzed 1,094 sample pairs of 1 ml of plasma and 10 microl of WB from donors confirmed to be HIV positive. The probability of detecting HIV nucleic acids in 10 microl of blood was 59.3% (95% confidence interval, 54.9 to 63.6%), 85.1% (80.0 to 90.2%), 91.5% (88.1 to 95%), and 100% when the corresponding plasma samples had an undetectable VL, a detectable VL less than 40 viral copies/ml (cp/ml), a VL between 40 and 4,000 cp/ml, and a VL greater than 4,000 cp/ml, respectively. Capillary blood and venous blood yielded comparable diagnostic sensitivities. Furthermore, our data indicate that WB could be used to monitor VL changes after highly active antiretroviral therapy (HAART) started. Thus, we have demonstrated the feasibility of small volumes of venous and finger-stick WB as valid samples for VL testing. This approach should facilitate the development of robust point-of-care HIV VL tests.

Measuring human immunodeficiency virus type 1 RNA loads in dried blood spot specimens using NucliSENS EasyQ HIV-1 v2.0

BACKGROUND

HIV-1 RNA plasma level is a key parameter for anti-viral treatment monitoring in HIV-1 infected individuals. Plasma stability and accurate measurement of clinical state is at risk when transporting from remote areas. Dried blood spot (DBS) testing can reduce this risk.

OBJECTIVES

Determine the performance of NucliSENS EasyQ HIV-1 v2.0 for DBS.

STUDY DESIGN

100 HIV-1 negative, and 129 HIV-1 spiked blood specimens (2180 copies/ml) were used for diagnostic specificity and system robustness. Analytical performance was tested in the range 50-85,000,000 copies/ml. Clinical reactivity was measured with specimens obtained from 224 HIV-1 infected individuals. HIV-1 RNA stability was analyzed after applying several different storage conditions.

RESULTS

Diagnostic specificity was 100% and system robustness was demonstrated by 100% detection rate without invalids. Limit of detection (95% detection rate) was 800 copies/ml. Linear results were obtained over the whole range tested. For clinical specimens, percentage positive results were comparable for DBS (57%) and plasma (58%). DBS quantification was on average 0.36log10 lower as compared to plasma. Specimen stability was demonstrated for 1 week at 55 degrees C/60% humidity, 3 weeks at 37 degrees C/80% humidity, 9 weeks at 37 degrees C/40% humidity, 3 months at -20 degrees C/70% humidity, 3 weeks at 4 degrees C/100% humidity, 9 months at room temperature (15-30 degrees C), and 9 weeks shipment simulation.

CONCLUSION

Results obtained fully support the use of DBS for the NucliSENS EasyQ HIV-1 v2.0 assay. These findings are especially of importance in cases that plasma stability is currently at risk due to for example, long transport routes from remote areas under less controlled conditions.

Measure of viral load by using the Abbott Real-Time HIV-1 assay on dried blood and plasma spot specimens collected in 2 rural dispensaries in Cameroon

BACKGROUND

This study aimed to evaluate the use of dried blood spots (DBSs) and dried plasma spots (DPSs) locally collected in 2 rural dispensaries in Cameroon for the quantification of HIV-1 RNA.

METHODS

Forty-one subjects were sampled and spots of whole blood and plasma were deposited onto Whatman 903 cards and dried at ambient temperature under local conditions. Two sets of DBS and DPS cards were done per patient. The rest of the liquid plasma (LP) was frozen until use. LPs were tested at the "Chantal Biya" International Reference Centre (Yaoundé, Cameroon) by the Abbott Real-Time HIV-1 assay (Abbott Molecular Diagnostics, Wiesbaden, Germany). One series of DBS and DPS was transported and tested between 2 and 6 weeks later at the Virology Laboratory of Saint-Etienne (France). The second series was routed by mail and tested after up to 3 months of storage at ambient temperature.

RESULTS

From the first series, the correlation rate between viral loads obtained from LP and DBS, and from LP and DPS, was 0.98 and 0.99, respectively; specificity of DBS and DPS results was 100%. The results obtained from the second series indicate a great stability of DBS after long-term storage.

CONCLUSION

This study demonstrates that DBSs collected under local conditions in resource-limited settings are suitable for the differed quantification of HIV-1 RNA.

Update on HIV viral-load assays: new technologies and testing in resource-limited settings

Assessment of viral load is one of the best predictors of clinical progression, as well as the main parameter to assess treatment response in HIV-positive patients. Reproducible and sensitive assays based on real-time PCR technology have been developed to quantify HIV in the bloodstream of infected persons. Recent improvements have allowed reliable measurements of viremia in non-B subtypes. Testing of samples other than serum or plasma has been challenging, but is particularly important for developing countries.

Monitoring HIV vaccine trial participants for primary infection: studies in the SIV/macaque model

OBJECTIVES

The ability to detect and quantify acute HIV-1 infection prior to seroconversion would be an important tool for use in HIV vaccine clinical efficacy trials. We have utilized the SIV/rhesus monkey model to evaluate whether samples more easily obtained than peripheral blood might be used for intensive monitoring of vaccine trial participants.

METHODS

We have evaluated viral loads in peripheral blood, saliva, feces, and urine of five rhesus monkeys during primary SIVmac251 infection by quantitative real-time PCR. As an alternative to the direct monitoring of frozen samples, we have also developed a fully quantitative viral load assay utilizing dried blood spots.

RESULTS

Although all compartments were found to harbor viral RNA during primary infection, viral RNA could be detected in the peripheral compartments only when levels of plasma viremia exceed a threshold value of 10 RNA copies/ml. We found no direct correlation between viral burden in plasma and saliva, feces, or urine viral loads. Importantly, both dried saliva and whole blood spots can be used for viral detection. Quantitative whole blood or plasma spotting correlated well with viral burden in plasma during both the acute and set point phase of infection.

CONCLUSION

Dried blood spots are amenable to rapid quantitative viral load testing. Whole blood spotting has a significant logistical benefit as it requires low blood volumes and no blood processing. Saliva or dried saliva spots or both are potential candidates for acute phase diagnostic screening. These studies indicate the feasibility of intensive monitoring of HIV-1 vaccine trial participants for virus acquisition in resource-limited settings.

Dried Fluid Spots for HIV Type-1 Viral Load and Resistance Genotyping: A Systematic Review

Background

Dried spots on filter paper made of whole blood (dried blood spots; DBS), plasma (dried plasma spots; DPS) or serum (dried serum spots) hold promise as an affordable and practical alternative specimen source to liquid plasma for HIV type-1 (HIV-1) viral load determination and drug resistance genotyping in the context of the rapidly expanding access to antiretroviral therapy (ART) for HIV-1-infected individuals in low- and middle-income countries. This report reviews the current evidence for their utility.

Methods

We systematically searched the English language literature published before 2009 on Medline, the websites of the World Health Organization and US Centers for Disease Control and Prevention, abstracts presented at relevant international conferences and references from relevant articles.

Results

Data indicate that HIV-1 viral load determination and resistance genotyping from DBS and DPS is feasible, yielding comparable test performances, even after storage. Limitations include reduced analytical sensitivity resulting from small analyte volumes (approximately 3.5 log10 copies/ ml at 50 ml sample volume), nucleic acid degradation under extreme environmental conditions, impaired efficiency of nucleic acid extraction, potential interference of archived proviral DNA in genotypes obtained from DBS and the excision of spots from the filters in high-volume testing.

Conclusions

This technology offers the advantages of a stable specimen matrix, ease of sample collection and shipment. The current sensitivity in drug resistance testing is appropriate for public health surveillance among pretreatment populations. However, consistently improved analytical sensitivity is needed for their routine application in the therapeutic monitoring of individuals receiving ART, particularly at the onset of treatment failure.

Detection and genotyping of human papillomavirus in self-obtained cervicovaginal samples by using the FTA cartridge: new possibilities for cervical cancer screening

This study assesses human papillomavirus (HPV) detection and genotyping in self-sampled genital smears applied to an indicating FTA elute cartridge (FTA cartridge). The study group consisted of 96 women, divided into two sample sets. All samples were analyzed by the HPV SPF(10)-Line Blot 25. Set 1 consisted of 45 women attending the gynecologist; all obtained a self-sampled cervicovaginal smear, which was applied to an FTA cartridge. HPV results were compared to a cervical smear (liquid based) taken by a trained physician. Set 2 consisted of 51 women who obtained a self-sampled cervicovaginal smear at home, which was applied to an FTA cartridge and to a liquid-based medium. DNA was obtained from the FTA cartridges by simple elution as well as extraction. Of all self-obtained samples of set 1, 62.2% tested HPV positive. The overall agreement between self- and physician-obtained samples was 93.3%, in favor of the self-obtained samples. In sample set 2, 25.5% tested HPV positive. The overall agreement for high-risk HPV presence between the FTA cartridge and liquid-based medium and between DNA elution and extraction was 100%. This study shows that HPV detection and genotyping in self-obtained cervicovaginal samples applied to an FTA cartridge is highly reliable. It shows a high level of overall agreement with HPV detection and genotyping in physician-obtained cervical smears and liquid-based self-samples. DNA can be obtained by simple elution and is therefore easy, cheap, and fast. Furthermore, the FTA cartridge is a convenient medium for collection and safe transport at ambient temperatures. Therefore, this method may contribute to a new way of cervical cancer screening.

Dried-plasma transport using a novel matrix and collection system for human immunodeficiency virus and hepatitis C virus virologic testing

A novel method for the collection and transportation of dried-blood-plasma samples, SampleTanker (ST), was developed and compared to standard shipping protocols for frozen-plasma specimens containing human immunodeficiency virus type 1 (HIV-1) and/or hepatitis C virus (HCV). Matched frozen and dried 1-ml EDTA-containing plasma samples were collected and analyzed by several molecular-based virologic assays. After addition of 1.175 ml of reconstitution buffer, 1.035 ml of dried plasma was recovered. Mean intra-assay variances were 0.05, 0.05, and 0.06 log(10) copies/ml for the Versant, Amplicor, and NucliSens QT HIV-1 load assays, respectively (P, not significant). However, mean HIV-1 viral load was consistently reduced in dried samples by 0.32 to 0.51 log(10) copies/ml, depending on assay type (P < 0.05). Infectious HIV-1 was not recovered from dried ST plasma. There was no significant difference in HIV-1 viral load results obtained using ST after 8 weeks of storage at ambient temperature. Compared to frozen plasma, HIV-1 genotypic results were >99% concordant at the nucleotide and amino acid levels, as well as for resistance-associated mutations. We further demonstrated successful detection of multiple analytes, including HIV-1 viral load, HIV-1 antiretroviral resistance genotype, and HCV genotype, from a single ST unit. Dried plasma collected with ST yielded comparable results to frozen samples for multiple-analyte clinical testing. As such, ST could be a useful alternative for virologic tests and clinical trials worldwide by significantly diminishing transportation cost and the sample volume restrictions associated with dried-blood-spot technology.

Detection of HIV-1 in alternative specimen types using the APTIMA HIV-1 RNA Qualitative Assay

Peripheral blood mononuclear cells (PBMCs), saliva, seminal plasma, and dried blood spots were evaluated as specimen types for the APTIMA HIV-1 RNA Qualitative Assay (APTIMA HIV-1 Assay), which employs a target capture step to recover HIV-1-specific sequences from complex specimen types. Analytical sensitivity studies were carried out using samples that were either diluted or eluted with a buffered detergent and spiked with different concentrations of HIV-1 ranging from 1 to 10,000 copies/mL. PBMC samples spiked with HIV-1 had comparable analytical sensitivity to HIV-1 spiked plasma with a 95% limit of detection of 13.1 and 17.2 copies/mL, respectively. Analytical sensitivity in seminal plasma specimens diluted 1:5 and saliva diluted 1:2 was comparable to HIV-1 spiked dilution buffer alone. Whole blood and dried blood spot specimens spiked with HIV-1 had equivalent reactivity at 250 copies/spot (5000 copies/mL). However, the 95% limit of detection values were significantly different (293.7 copies/mL for whole blood and 2384 copies/mL for dried blood spot specimens). No significant effect on analytical sensitivity was observed when one HIV-1 positive dried blood spot punch was pooled with up to 9 HIV-1 negative dried blood spot punches. Together, these studies demonstrate that the APTIMA HIV-1 RNA Qualitative Assay can be used to process a diverse array of specimen types with minimal impact on analytical sensitivity for most specimen types.

Correlation between human immunodeficiency virus type 1 (HIV-1) RNA measurements obtained with dried blood spots and those obtained with plasma by use of Nuclisens EasyQ HIV-1 and Abbott RealTime HIV load tests

The plasma human immunodeficiency virus (HIV) RNA load is used in the clinical routine for the monitoring of HIV infection and the patient's response to antiretroviral therapy. Other body fluids or dried blood spots (DBS) can be used, however, to assess the level of viremia. The use of DBS may be especially helpful for the monitoring of HIV-infected patients in resource-poor settings, where access to adequate laboratory facilities is often difficult. However, the correlation between the HIV RNA levels in plasma and those in DBSs has not been well established. Paired plasma and DBS samples obtained from HIV type 1 (HIV-1)-infected patients were tested for HIV RNA copy numbers by using two different commercial assays, the Nuclisens EasyQ HIV-1 (version 1.1) test (the Nuclisens test; Biomerieux) and the m2000rt RealTime HIV test (the m2000rt test; Abbott). Nucleic acid extraction was performed manually by using either the Nuclisens isolation kit (which uses the Boom methodology) or the m2000rt sample preparation kit (an iron particle-based method). A total of 103 paired plasma and DBS samples were tested. Viral load results were obtained for 97 (94.2%) samples with the Nuclisens isolation kit and 81 (78.6%) samples with the m2000rt kit. The overall correlation between the RNA loads in plasma and DBS was good, although better results were obtained by the Nuclisens test (R(2) = 0.87, P < 0.001) than by the m2000rt test (R(2) = 0.70, P < 0.001). While the specificities were excellent and similar for both the Nuclisens and the m2000rt tests (97.1% and 100%, respectively), the sensitivity was greater by the Nuclisens test than by the m2000rt test (75.8% and 56.6%, respectively). Overall, the viral loads in DBS tended to be lower than those in plasma, with mean differences of 0.3 log unit (standard deviation, 0.5 log unit) and 0.76 log unit (standard deviation, 0.8 log unit) for the Nuclisens and the m2000rt tests, respectively. The levels of agreement between the measurements in plasma and DBS were assessed by using the Bland-Altman plot for each assay. The Nuclisens test gave results within its defined limits (-0.65 to 1.26) for 95.9% of the samples, while the m2000rt test gave results within its limits (-0.83 to 2.33) for 100% of the samples. In summary, the HIV-1 load can accurately be quantified by testing DBS by either the Nuclisens or the m2000rt test, although the Nuclisens test may outperform the m2000rt test when nucleic acids are extracted manually.

Evaluation of different RNA extraction methods and storage conditions of dried plasma or blood spots for human immunodeficiency virus type 1 RNA quantification and PCR amplification for drug resistance testing

The development and validation of dried sample spots as a method of specimen collection are urgently needed in developing countries for monitoring of human immunodeficiency virus (HIV) infection. Our aim was to test some crucial steps in the use of dried spots, i.e., viral recovery and storage over time. Moreover, we investigated whether dried plasma and blood spots (DPS and DBS, respectively) give comparable viral load (VL) results. Four manual RNA extraction methods from commercial HIV type 1 (HIV-1) VL assays--a QIAamp minikit (Qiagen), the Abbott Molecular sample preparation system, the Nuclisens assay (bioMarieux), and High Pure viral nucleic acid kit (Roche Applied Science)--were compared for VL quantification and PCR amplification for genotypic drug resistance testing on dried spots from spiked plasma and residual samples from HIV-1 patients (n = 47; median VL, 4.13 log(10) copies/ml). RNA recovery from DPS was efficient using Nuclisens extraction (median difference, 0.03 log(10) copies/ml) and slightly underestimated using the Abbott Molecular sample preparation system (median difference, 0.35 log(10) copies/ml). PCR amplification results were in concordance. Measurements from DBS overestimated VL for plasma, with VL results showing <3.7 log(10) copies/ml. VL was stable for up to 3 months in spiked DPS stored at 20 degrees C but for only 1 month at 37 degrees C. A faster decline was observed in PCR efficiency: DPS could be stored for 1 week at 37 degrees C and for 1 month at 20 degrees C. In conclusion, the RNA extraction method is an important factor in obtaining reliable RNA quantification and PCR amplification of HIV-1 on DPS/DBS. DBS could be used as an alternative for DPS depending on HIV RNA cutoffs for virological failure. VL measurements remain stable over a longer period than do PCR amplification results.

Dried-blood sampling for epstein-barr virus immunoglobulin G (IgG) and IgA serology in nasopharyngeal carcinoma screening

Dried-blood (DB) samples on filter paper are considered clinical specimens for diagnostic use because of the ease of collection, storage, and transport. We recently developed a synthetic-peptide-based immunoglobulin A (IgA) (EBNA1 plus viral capsid antigen [VCA]-p18) enzyme-linked immunosorbent assay (ELISA) for nasopharyngeal carcinoma (NPC) screening. Here, we evaluate the use of two filter papers for DB sampling, i.e., Schleicher & Schuell (S&S) no. 903 and Whatman no. 3; the DB samples were either taken directly from a finger prick or spotted from a Vacutainer blood collector. The elution of DB samples on filter paper was optimized and tested for IgG and IgA reactivity by ELISA (EBNA1 plus VCA-p18) and compared to simultaneously collected plasma samples. The results showed that both types of filter paper can be used for sample collection in NPC diagnosis by using either finger prick or blood spot sampling. Both DB sampling methods produced comparable ELISA (EBNA1 plus VCA-p18) results for IgG and IgA reactivity in 1:100-diluted plasma samples. DB samples of whole blood or finger prick blood show correlation coefficients (r(2)) of 0.825 to 0.954 for IgA on S&S no. 903 filter paper, 0.9133 to 0.946 for IgA on Whatman no. 3 filter paper, 0.807 to 0.886 for IgG on S&S no. 903 filter paper, and 0.819 to 0.934 for IgG on Whatman no. 3 filter paper. Using plasma IgA as a reference, DB sampling showed sensitivities and specificities of 75.0 to 96.0% and 93.5 to 100%, respectively. DB samples could be stored at 37 degrees C for 1 to 4 weeks on S&S no. 903 filter paper and 1 to 6 weeks on Whatman no. 3 filter paper without a significant loss of reactivity, with provision of transport options for tropical conditions. IgA proved to be more stable than IgG. Whatman no. 3 filter paper is a more economical yet diagnostically comparable alternative to S&S no. 903 filter paper. Finger prick DB sampling is proposed for NPC diagnosis, particularly for remote hospitals and field screening studies.

Feasibility of detecting human immunodeficiency virus type 1 drug resistance in DNA extracted from whole blood or dried blood spots

Due to high cost, availability of human immunodeficiency virus type 1 (HIV-1) drug resistance testing in resource-poor settings is still limited. We therefore evaluated the usefulness of viral DNA extracted from either whole blood or dried blood spots (DBS). Samples were collected from 50 patients receiving therapy and 10 therapy-naïve patients. Amplification and sequencing of RNA and DNA was performed using an in-house assay. Protease (PR) and reverse transcriptase (RT) sequences of plasma viral RNA were obtained for 96.6% and 89.7%, respectively, of the 29 patients with a detectable viral load. For cellular viral DNA, useful PR and RT sequences were obtained for 96.6% and 93.1% of the whole-blood-cell samples and for 93.1% and 93.1% of the DBS samples, respectively. For the 31 patients with an undetectable viral load, PR and RT sequences were obtained for 67.7% and 61.3% of the whole-blood-cell DNA preparations and for 54.8% and 58.1% of the DBS DNA preparations, respectively. A good correlation between RNA and DNA sequences was found; most discordances were caused by the detection of mixed amino acids. Of the RT drug-resistant mutations, 13 (38.2%) were seen in RNA only, 6 (17.6%) in DNA only, and 15 (44.1%) in both. Repeated amplification and sequencing of DNA extracts revealed a lack of reproducibility for the detection of drug resistance mutations in a number of samples, indicating a possible founder effect. In conclusion, this study shows the feasibility of genotypic drug resistance testing on whole blood cells or DBS and its possible usefulness for HIV-1 subtyping or examining the overall distribution of drug resistance in a population. For individual patients, RNA sequencing was shown to be superior to DNA sequencing, especially for patients who experienced early treatment failure. The use of DNA extracted from whole blood or DBS for the detection of archived drug resistance mutations deserves further study.