Monitoring of SARS-CoV-2 antibodies using dried blood spot for at-home collection

Evaluation of SARS-CoV-2 Antibody Response Between Paired Fingerprick (HemaPEN®) and Venepuncture Collected Samples in Children and Adults

Serological surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies is important to monitor population COVID-19 immunity. Dried blood spots (DBS) are a valuable method for serosurveys, particularly in remote settings and in children. We compared the measurement of SARS-CoV-2 spike-specific IgG in paired blood samples collected using standard venepuncture (serum) and the hemaPEN® microsampling DBS device from children and adults. A total of 83 participants (10 months to 65 years of age), comprising COVID-positive and -negative participants, were recruited. Paired serum and DBS samples were assayed for SARS-CoV-2 receptor-binding domain (RBD) and Spike (S1) antibodies using an established in-house ELISA. RBD and S1 IgG concentrations of paired hemaPEN DBS eluates and serum samples were compared using a non-parametric Wilcoxon matched-pairs signed ranked test. A Pearson's correlation was used for RBD and S1 IgG concentrations and the level of agreement between the hemaPEN DBS eluates and serum samples was assessed by Bland-Altman analysis. A total of N = 41 adults (36 COVID-positive and 5 COVID-negative), and N = 42 children (37 COVID-positive, and 5 COVID-negative) have paired serum and DBS assayed. We found moderate to strong correlations between paired hemaPEN DBS eluates and serum SARS-CoV-2 IgG antibodies for RBD (r = 0.9472, p < 0.0001) and S1 proteins (r = 0.6892, p < 0.0001). Similar results were observed in both adult and paediatric populations. No significant differences in S1-specific IgG levels were observed in hemaPEN DBS samples stored for up to 35 weeks at room temperature. Eluted hemaPEN samples showed high specificity and sensitivity (100% and 89.89%, respectively) compared with serum. The use of the microsampling hemaPEN device for DBS sample collection is a feasible approach for assessing SARS-CoV-2 antibodies for serosurveillance studies, particularly in remote settings and in children.

Performance of patient-collected dried blood specimens for HIV-1 viral load testing in South Africa

OBJECTIVE

Evaluate the clinical utility of patient-collected dried blood spots (DBS) in measuring HIV-1 viral load (VL) for monitoring antiretroviral therapy (ART) compared to provider-collected DBS and blood plasma.

DESIGN

In a randomized trial of community-based delivery of ART in South Africa, we assessed performance of: DBS specimens compared to plasma, and participant-collected vs. staff-collected DBS specimens, to measure HIV-1 VL.

METHODS

The bioMérieux NucliSENS EasyQ HIV-1 v2.0 assay was used for VL measurement. From October 2017 to November 2019, we collected 996 pairs of plasma/DBS specimens from 760 participants and 315 pairs of staff-/participant-collected DBS cards from 261 participants. We assessed DBS test sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) using the WHO failure threshold of 1000 copies/ml. Log-transformed VL was compared using concordance correlation coefficients (CCC) and mean differences from linear mixed models.

RESULTS

In a population with 13% detectable VL, DBS VL compared with plasma VL had 91% [95% confidence interval (CI): 86-95] sensitivity, 99% (98-100) specificity, 94% (90-98) PPV, and 99% (98-99) NPV. We observed high agreement between staff-collected DBS VL and plasma VL (CCC: 0.94), and between participant-collected DBS VL and plasma VL (CCC: 0.92). We did not observe a statistically significant difference between participant- and staff-collected DBS VL and correlation was very high (CCC: 0.97).

CONCLUSIONS

VL results from participant-collected DBS are clinically comparable with those collected by clinical staff and using blood plasma. Self-collected DBS has potential for use for ART monitoring outside the clinic.

Short- and long-term stability of SARS-CoV-2 antibodies on dried blood spots under different storage conditions

Dried blood spots (DBS) are broadly used for different serological analyses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody assessment. In order to biobank DBS samples, an understanding of the preservation of SARS-CoV-2 antibodies is needed. Therefore, we assessed the stability of SARS-CoV-2 antibodies on DBS during short- and long-term storage under different storage temperatures. Seven sample donors were enrolled, each donating twenty 6 mm DBS to assess anti-spike (S1) SARS-CoV-2 IgG antibodies (EUROIMMUN). Baseline samples were analyzed on the day of collection. The remainder of the samples was stored in grip seal bags kept in a cryobox at room temperature/4°C until 2 months after collection and at -20°C until 2 years after collection. Samples were analyzed at regular intervals within the total storage duration and after one and five freeze-thaw cycles. A pooled coefficient of variation was calculated for each storage temperature. We found that anti-S1 SARS-CoV-2 antibodies collected on DBS saver cards remain stable during short-term storage at RT, 4°C, and -20°C (at least to 2 months) and long-term storage at -20°C (at least 2 years). Moreover, up to five freeze-thaw cycles can occur without impacting the anti-S1 SARS-CoV-2 antibody level. The inter-assay coefficient of variation lies between 10 and 15%. As DBS can be preserved for both shorter periods of time at RT and longer periods of time at -20°C, they are a perfect application for studies that require sample shipment by mail, self-sampling studies, studies in limited resource settings and biobanking.IMPORTANCEDried blood spots (DBS) are currently widely used as a microsampling technique for different qualitative and quantitative serological assessments. Yet, there is a lack of long-term stability and storage condition studies. In our study, first, we assessed the stability of SARS-CoV-2 antibodies on DBS up to 2 years post-collection. We believe that our data are not only important for future COVID-19 research but also for studies on other infections/diseases using DBS-based serology.

Use of dried blood spots in the detection of coronavirus disease 2019 (COVID-19): A systematic review

INTRODUCTION

COVID-19 disease continues to be a global health concern. The current protocol for detecting SARS-CoV-2 requires healthcare professionals to draw blood from patients. Recent studies showed that dried blood spot (DBS) is a valuable sampling procedure that can collect a low blood volume without the need for the presence of medical practitioners. This study synthesized the available literature on using DBS as a blood collection tool to diagnose COVID-19 disease.

MATERIALS AND METHODS

A comprehensive search utilizing OVID, CINAHL, and Scopus databases was done from inception to March 2023. Five reviewers collected, extracted and organized the study data.

RESULTS

This systematic review included 57 articles. DBS was commonly prepared by finger pricking. Most studies showed more favorable results and longer sample stability (more than 1080 days) with lower storage temperature conditions for the DBS. DBS samples were mostly used for serological assays for COVID-19 disease detection. ELISA was the most used detection method (43.66 %). Diagnostic performance of laboratory tests for COVID-19 using DBS sample showed high sensitivity of up to 100 % for immunoassay tests and 100 % specificity in agglutination, PCR, and DELFIA assays.

CONCLUSION

DBS sampling coupled with serological testing can be an alternative method for collecting blood and detecting COVID-19 disease. These tests using DBS samples showed excellent diagnostic performance across various geographic locations and demographics.

Transmission of SARS-CoV-2 among underserved pastoralist communities in Kajiado County, Kenya: 2020-2022

Initial transmission of severe acute respiratory syndrome virus-2 (SARS-CoV-2) was highest in densely populated regions of Kenya. Transmission gradually trickled down to the less densely populated, remote and underserved regions such as the pastoral regions of Kajiado County which are characterized by poor healthcare systems. Molecular assays that were pivotal for COVID-19 diagnosis were not available in these regions. Serology is an alternative method for retrospectively tracking the transmission of SARS-CoV-2 in such populations. Dry blood spots (DBS) were prepared from consenting patients attending six health facilities in Kajiado County from March 2020 to March 2022. Upon elution, we conducted an enzyme-linked immunosorbent assay (ELISA) for the detection of SARS-Cov-2 IgG antibodies. Of the 908 DBSs we analyzed, 706 (78%) were from female participants. The overall seropositivity to SARS-Cov-2 antibodies was 7.3% (95% CI 5.7-9.1). The elderly (over 60 years) and male participants had a high likelihood of testing positive for SAR-CoV-2 infections. Mashuru (15.6%, 14/90) and Meto (15%, 19/127) health facilities registered the highest proportion of seropositive participants. Evidence of SARS-CoV-2 transmission among pastoralists in the remote and underserved regions of Kajiado County was established by DBS sampling and serologic testing.

Using Dried Blood Spots to Quantitatively Detect Anti-SARS-CoV-2 IgG Antibodies by ELISA: A Validation Study

SARS-CoV-2 serological testing is useful to determine seroprevalence, epidemiological trends, and the extent of transmission. The collection and transport of serum samples can be logistically challenging, especially in remote underserved areas. Dried blood spots (DBSs) would allow easier sample collection and logistical handling compared with standard serum collection, particularly for extensive and repeated SARS-CoV-2 serosurveys. We evaluated the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the IgG ELISA (Wantai, Beijing, China) using DBSs against sera for the quantitative detection of SARS-CoV-2 IgG antibody. The IgG ELISA was used to test paired sera and DBSs obtained from individuals with recent virologically confirmed COVID-19 illness and banked paired sera and DBSs collected before the COVID-19 pandemic. We found that 100/100 (100%) seropositive samples were positive using DBSs, and 193/194 (99%) seronegative samples were negative using DBSs. Compared with sera, the DBS method had a 100% sensitivity, 99% specificity, 99% PPV, and 100% NPV. Use of DBSs for SARS-CoV-2 household or population serosurveys may be considered in situations with limitations in sample collection, shipment, and storage.

Validity of dried blood spot testing for sexually transmitted and blood-borne infections: A narrative systematic review

Testing for human immunodeficiency virus (HIV) and hepatitis C virus (HCV) using dried blood spot (DBS) specimens has been an integral part of bio-behavioural surveillance in Canada for almost two decades, though less is known regarding the use of DBS in surveillance of other sexually transmitted and blood-borne infections (STBBI). A systematic review was conducted using a peer-reviewed search strategy to assess the current evidence regarding the validity of STBBI testing using DBS specimens. Eligibility criteria included studies reporting use of DBS specimens for STBBI testing with either commercially available or "in-house" tests in populations 15 years of age or older. Studies reporting a measure of validity such as sensitivity, specificity, positive and negative predictive values were eligible for inclusion. Quality of studies and risk of bias were assessed using the QUADAS-2 tool. A total of 7,132 records were identified. Of these, 174 met the criteria for inclusion. Among the studies that reported validity measures, a substantial proportion demonstrated high sensitivity (≥90%) in 62.5% of cases (N = 334/534 sensitivity measurements), and high specificity (≥90%) was observed in 84.9% of instances (N = 383/451 specificity measurements). However, the quality of the studies varied greatly. Our findings support the validity of the use of DBS specimens in STBBI testing where sufficient evidence was available, but validity is highly dependent on thorough method development and validation.

High pre-Delta and early-Omicron SARS-CoV-2 seroprevalence detected in dried blood samples from Kinshasa (D.R. Congo)

Studies on the impact of the COVID-19 pandemic in sub-Saharan Africa have yielded varying results, although authors universally agree the real burden surpasses reported cases. The primary objective of this study was to determine SARS-CoV-2 seroprevalence among patients attending Monkole Hospital in Kinshasa (D.R. Congo). The secondary objective was to evaluate the analytic performance of two chemiluminescence platforms: Elecsys® (Roche) and VirClia® (Vircell) on dried blood spot samples (DBS). The study population (N = 373) was recruited in two stages: a mid-2021 blood donor cohort (15.5% women) and a mid-2022 women cohort. Crude global seroprevalence was 61% (53.9%-67.8%) pre-Delta in 2021 and 90.2% (84.7%-94.2%) post-Omicron in 2022. Anti-spike (S) antibody levels significantly increased from 53.1 (31.8-131.3) U/mL in 2021 to 436.5 (219.3-950.5) U/mL in 2022 and were significantly higher above 45 years old in the 2022 population. Both platforms showed good analytic performance on DBS samples: sensitivity was 96.8% for IgG (antiN/S) (93.9%-98.5%) and 96.0% (93.0%-98.0%) for anti-S quantification. These results provide additional support for the notion that exposure to SARS-CoV-2 is more widespread than indicated by case-based surveillance and will be able to guide the pandemic response and strategy moving forward. Likewise, this study contributes evidence to the reliability of DBS as a tool for serological testing and diagnosis in resource-limited settings.

Dried blood spot eluates are suitable for testing of SARS-CoV-2 IgG antibodies targeting Spike protein 1 and Nucleocapsid protein

Dried blood spots (DBS) provide easy handling and are thus a beneficial tool for data collection, e.g. for epidemiological studies. The suitability of DBS for the assessment of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was analyzed with regards to the use in future studies addressing seroprevalence in the population. 121 volunteers gave a venous blood sample and capillary blood samples on two DBS cards (PerkinElmer and Ahlstrom-Munksjö) via self-sampling under supervision. All samples were analyzed using the Anti-SARS-CoV-2 ELISA (IgG) and the Anti-SARS-CoV-2 NCP ELISA (IgG) from EUROIMMUN performed on the EUROIMMUN EUROLabWorkstation ELISA. Correlation coefficients between ELISA results based on the different sampling methods were calculated. Results of DBS analysis for SARS-CoV-2 IgG S1 and NCP highly correlated with the serum values (r = 0.96). In addition, the calculation of the phi coefficient showed no significant difference between the qualitative results of both sampling methods (r_φ = 0.98-1.0). Further analysis of DBS eluates after prolonged storage of 6-8 h also showed a high correlation with serum results (r = 0.97 and r = 0.93, respectively). The study results indicate suitability of DBS for the analysis of antibodies against SARS-CoV-2 S1 and NCP. For DBS eluate, a stability of 6-8 h for measurement of SARS-CoV-2 antibodies can be assumed.

Feasibility of remote self-collection of dried blood spots, hair, and nails among people with HIV with hazardous alcohol use

BACKGROUND

The use of biomarkers in behavioral HIV research can help to address limitations of self-reported data. The COVID-19 pandemic forced many researchers to transition from standard in-person data collection to remote data collection. We present data on the feasibility of remote self-collection of dried blood spots (DBS), hair, and nails for the objective assessment of alcohol use, antiretroviral therapy adherence, and stress in a sample of people with HIV (PWH) who are hazardous drinkers.

METHODS

Standardized operating procedures for remote self-collection of DBS, hair, and nails were developed for an ongoing pilot study of a transdiagnostic alcohol intervention for PWH. Prior to each study appointment, participants were mailed a kit containing materials for self-collection, instructions, a video link demonstrating the collection process, and a prepaid envelope for returning samples.

RESULTS

A total of 133 remote study visits were completed. For DBS and nail collection at baseline, 87.5% and 83.3% of samples, respectively, were received by the research laboratory, of which 100% of samples were processed. Although hair samples were intended to be analyzed, most of the samples (77.7%) were insufficient or the scalp end of the hair was not marked. We, therefore, decided that hair collection was not feasible in the framework of this study.

CONCLUSION

An increase in remote self-collection of biospecimens may significantly advance the field of HIV-related research, permitting the collection of specimens without resource-intensive laboratory personnel and facilities. Further research is needed on the factors that impeded participants' ability to complete remote biospecimen collection.

Stabilization and quantitative measurement of nicotinamide adenine dinucleotide in human whole blood using dried blood spot sampling

Nicotinamide adenine dinucleotide (NAD⁺) is a coenzyme essential for energy production. Recently, associations between NAD⁺ and aging-related diseases have been reported, and NAD⁺ precursors that increase NAD⁺ concentration in the body have been acknowledged as anti-aging supplements. However, there have been only a few studies on the link between aging or aging-related diseases and human blood NAD⁺ concentration because NAD⁺ and its precursors are unstable in blood and difficult to measure. Therefore, we aimed to construct a quantitative NAD⁺ measurement method that is simpler than the existing methods. The calibration standards of NAD⁺ showed good linearity (0.9936 to 0.9990) in the range of 0.25 to 200 μM, and the lower limit of quantification was 0.5 to 2 μM. We found that QIAcard FTA DMPK-B maintained NAD⁺ stability of 85% or more for at least 2 weeks at 4 °C and 1 week at room temperature using the dried blood spot method. Additionally, NAD⁺ stability in the blood extraction solution was more than 90% for 2 months. To our knowledge, there has been no report on a quantitative NAD⁺ measurement method in human whole blood that can be performed with as little as 5 μL of blood and can be easily implemented at both medical clinics and private homes. Our simple and convenient method has the potential to become the gold standard for NAD⁺ measurement in blood. It is expected to contribute to the acceleration of research on the correlation between aging or aging-related diseases and NAD⁺ concentration in human blood.

A Highly Sensitive Immunoassay for Determination of Immune Response to SARS-CoV-2 in Capillary Blood Samples

Throughout the pandemic, serological assays have been revealed as crucial for detecting previous exposures to the virus and determining the timing of antibody maintenance after vaccination or natural infection. This study aimed to develop an optimized enzyme-linked immunosorbent assay (ELISA)-based serology, which could be used in case of reagent shortages, such as that occurred in the beginning of this health emergency. As a result, we present a high-sensitive immunoassay for the determination of IgG levels in venous serum samples, using 2 μg/mL antigen (receptor-binding domain of the spike protein S1) for coating the plate and utilizing human samples at a dilution 1:1000. This method showed non-inferiority features versus a commercial kit, is less expensive, and has a higher spectrophotometric range that allows for a better quantification of the antibody titers. The optical density values before and after heating venous serum samples at 56 °C during 30 min was quite similar, showing that heat inactivation can be used to reduce the biohazardous risks while handling samples. Furthermore, we show that finger-stick capillary blood samples can also serve as a suitable source for IgG detection, bypassing the need for serum isolation and being suitable for point-of-care application (Pearson's coefficient correlation with capillary serum was 0.95, being statistically significant).